Note: Descriptions are shown in the official language in which they were submitted.
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CHROMATOGRAPHY AND OTHER ADSORPTIONS
USING MODIFIED CARBON ADSORBENTS
FTFLT) OF't]KF TNVF',NTTnN
This invention relates to separation devices and processes as well as the use
of
modified carbonaceous materials as adsorbents and also relates to methods of
using these
adsorbents, including a method to increase the adsorption capacity and/or
alter the adsorption
affinity of carbonaceous materials capable of adsorbing an adsorbate.
Adsorption is an important operation in many industrial processes, The
effectiveness
of an adsorbent depends, primarily, on its surface area, pore structure, and
surface chemistry.
The nature of the adsorbate which is to be adsorbed frequently dictates the
chemical nature
of the adsorbent. For example, carbonaceous adsorbents are often used to
selectively remove
organic compounds from liquid, gaseous, or vapor media. Silica and alumina
based
adsorbents are employed to selectively adsorb polar adsorbates such as water,
ammonia, and
the like from similar media.
The efficacy of an adsorbent for a particular application is usually
determined by the
2 0 adsorption capacity and selectivity of the adsorbent for the adsorbate in
question. The
adsorption capacity may be measured per unit mass or per unit volume of the
adsorbent. In
general, the higher the adsorption capacity and selectivity of an adsorbent
for a particular
adsorbate, the more useful it is, since less of the adsorbent has to be used
to effect the same
removal of the adsorbate.
2 5 Carbonaceous materials, such as activated carbon, carbon black, and the
like,
represent an important class of adsorbents which are used in many fields such
as separation,
purification, and waste treatment, among others. Because oftheir widespread
use, any
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method for improving the adsorption properties of carbonaceous adsorbents for
a particular
adsorbate can have a large impact on the efficacy and economy of the processes
utilizing
them. Therefore, attempts have been made in the past to modify the surface
chemistry of
carbonaceous adsorbents. The methods employed for their modification can be
broadly
classified into physical and chemical means. In surface modification by
physical means, a
species is deposited on the surface of the carbonaceous adsorbent to form a
layer which then
changes its adsorption properties. However, such modification techniques have
limited
utility because the deposited layer is easily removed. In surface modification
by chemical
means, the modifying species is attached to the carbon surface by a chemical
bonding
mechanism.
The characteristics of the adsorption isotherm, representing the relationship
between
the extent of adsorption and adsorbate concentration or adsorbate partial
pressure at a fixed
temperature, is also of importance. As described by Sircar et al. in
"Activated Carbon for
Gas Separation and Storage," C:arhcn, Vol. 34, No. 1, pp. I-12 (1996), the
characteristics of
the preferred adsorption isotherm will depend on the separation process being
employed. For
example, in cases where adsorbent regeneration is effected by a pressure
swing, the preferred
adsorbent is one with a moderate affinity for the adsorbate. When the
adsorbate is strongly
adsorbed, that is, when it has a strong affinity for the adsorbent,
regeneration becomes
difficult and energy intensive. On the other hand, when the adsorbent exhibits
a weak
2 0 affinity for the adsorbate, it has a small adsorption capacity at low
adsorbent partial pressures
and, hence, the adsorption mass transfer zone becomes very long. Thus, the
availability of a
method for altering the affinity of an adsorbent for an adsorbate is
advantageous.
Thus, any method for increasing the adsorption capacity and/or modifying the
adsorption affinity of the adsorbent enhances its usefulness in adsorption
applications. As
2 5 already noted, chemical modification can be used to alter the adsorptive
properties of
carbonaceous adsorbents. The range of chemical species which can be attached,
however, is
limited.
Bansal, Donnet and Stoeckli (in Chapter 5 of Active (':arh~n, Marcel Dekker,
Inc.,
1988) have reviewed different techniques of carbon surface modification.
Physical
3 0 impregnation methods are described, as are methods that rely on chemical
reactions with
various species to modify the surface of the carbon. Some of the chemical
surface
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modification techniques described by Bansal et al. are oxidation,
halogenation, sulfonation,
and ammoniation. Several of these techniques require treatment of the carbon
at elevated
temperatures. Another technique involving oxidation of the carbon with HNOs in
the
presence of a catalyst, has been described by Sircar and Golden (U.S. Patent
No. 4,702,749).
However, these techniques have certain disadvantages apparent to those
familiar with the
field.
In chromatography and other separation methods, there is a certain amount of
selectivity and efficiency that is necessary in order for the stationary phase
to separate the
various components in a mixture. For this reason, carbon products, such as
carbon black,
graphite, and activated carbon, have not been used as a standard stationary
phase in certain
separation systems because carbon is a strong non-specific adsorbent. This has
been
disappointing in the past, because carbon products, otherwise, would have many
advantages
over commercially available adsorbents. For instance, there are no corrosion
problems with
carbon products, which are stable at a wide pH range unlike silica particles
which are stable
only in the pH range of 1-8, nor are there any swelling problems with carbon
products, which
are stable in all organic solvents, unlike polysaccharide and/or polymer-based
chromatographic particles, which have solvent restrictions. In addition,
carbon products can
be subjected to large temperature ranges and/or extreme pressures which would
be beneficial
for certain types of adsorptions, such as temperature swings used in some
types of
2 0 chromatography. In addition, with certain separation processes used in the
production of
biopharmaceuticals for clinical applications, the sterilization requirements
or
recommendations provide for the use of hot sodium hydroxide. With such
sterilization
procedures, the current popular stationary phases such as silica columns,
cannot be used.
Further, the polymeric columns such as cellulose polymers, are chemically but
not physically
stable to such sterilization treatments; in addition polymeric stationary
phases are typically
less e~cient than metal oxide based stationary phases, resulting in poorer
separations.
Accordingly, there is a need to provide a new class of adsorbents and new
separation
devices which can make use of carbon materials that have the advantages
described above
but are capable of being selective in their adsorption in order to serve as
suitable adsorbents
3 0 in separation processes such as chromatography.
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All patents, publications, and applications referenced throughout this
application are
incorporated in their entirety by reference herein and form a part of the
present application.
SUMMARY OF THF TNVF,NTT()N
To achieve these and other advantages and in accordance with the purposes of
the
present invention, as embodied and broadly described herein, the present
invention relates to
an adsorbent composition containing a modified carbonaceous material capable
of adsorbing
an adsorbate.
The present invention also relates to a separation device having a mobile
phase and a
stationary phase, wherein said stationary phase is a carbonaceous material
having attached at
least one organic group. The carbonaceous material having attached at least
one organic
group is capable of adsorbing one or more chemical species present in a
mixture.
The present invention further relates to a chromatography column containing a
column having a stationary phase and a mobile phase. The stationary phase is
at least a
carbonaceous material having attached at least one organic group wherein the
carbonaceous
material having at least one organic group is capable of adsorbing at least
one chemical
species present in a mixture.
The present invention further relates to a method for conducting
chromatography on
a substance and involves passing the substance through a column having a
stationary phase
2 0 and a mobile phase, wherein the stationary phase is at least a
carbonaceous material having
attached at least one organic group. The chromatography can be, for instance,
a size
exclusion chromatography, an affinity-type chromatography, an adsorption-
desorption
chromatography, or variations thereof or combinations thereof. Also, the
chromatography
can be a reverse phase chromatography, ion exchange chromatography,
supercritical fluid
chromatography, hydrophobic interaction chromatography, or chiral
chromatography.
The present invention, in addition, relates to bioseparations using the
chromatography methods described above.
The present invention also relates to separations using electrophoresis
wherein the
stationary phase is a carbonaceous material having attached at least one
organic group.
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The present invention further relates to a separation device containing a
membrane
wherein said membrane contains a carbonaceous material having attached at
least one
organic group.
The separation device can also be a magnetic separation device or a reverse
osmosis
device wherein the stationary phase or the membrane contains a carbonaceous
material
having attached at least one organic group.
Another embodiment of the present invention relates to a method to increase
the
adsorption capacity of a carbonaceous material capable of adsorbing an
adsorbate or altering
the adsorption isotherm of the adsorbate on the adsorbent, for instance, to
allow an easier
regeneration of the adsorbent. In this method, at least one organic group
capable of
increasing the adsorption capacity of a carbonaceous material is attached to
the carbonaceous
material.
The present invention, in addition, relates to a method of adsorbing an
adsorbate and
includes the step of contacting the adsorbate with a carbonaceous material
which has been
modified by attaching an organic group. The modified carbonaceous material is
capable of
adsorbing the adsorbate and at least one organic group is attached to the
carbonaceous
material.
Additional features and advantages of the present invention will be set forth
in part in
the description which follows, and in part will be apparent from the
description, or may be
learned by practice of the present invention. The objectives and other
advantages of the
present invention will be realized and attained by means of the elements and
combinations
particularly pointed out in the written description and appended claims.
It 'is to be understood that both the foregoing general description and the
following
detailed description are exemplary and explanatory only and are intended to
provide further
2 5 explanation of the present invention, as claimed.
The accompanying figures, which are incorporated in and constitute a part of
this
specification, illustrate several embodiments of the present invention and
together with the
description, serve to explain the principles of the present invention.
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Figure 1 is a graph plotting the amount of water adsorption on modified and
unmodified carbon black.
Figure 2 is a graph plotting the amount of water adsorption on modified and
unmodified activated carbon.
Figure 3 is a graph plotting the amount of water adsorption on modified and
unmodified carbon black per unit surface area.
Figure 4 is a graph plotting the amount of water adsorption on modified and
unmodified activated carbon per unit surface area.
Figure 5 is a graph plotting the amount of COa adsorption on modified and
unmodified carbon black at 273 IC.
Figure 6 is a graph plotting the concentration of supernatant vs. the
concentration of
loaded Bovine Serum Albumin (BSA) solution in the presence of various
carbonaceous
materials.
Figures 7-11 are various graphs plotting the separation of various analytes
resulting
from using various phases of the present invention.
DF,TATT,F,D DF~C'RTPTTON OF TTiF PRF~FNT TNVFNTTnN
The present invention relates to separation devices which typically have a
stationary
2 0 phase. The stationary phase, for purposes of the present invention, is a
carbonaceous material
having attached at least one organic group. This material is also known, once
the organic
group is attached, as a modified carbonaceous material for purposes of the
present invention.
The organic group is preferably attached (e.g., chemically) to the surfaces of
the
carbonaceous material, preferably by covalent bonds.
2 5 One preferred separation device is a chromatography column which, for
purposes of
the present invention, contains a column having a mobile phase and a
stationary phase. The
stationary phase is at least the modified carbonaceous material of the present
invention. The
mobile phase can be any conventional mobile phase used in the separation of
chemical
compounds or species from a mixture, such as solvents and the like. The
present invention
3 0 further relates to a method for conducting chromatography on a substance
or mixture which
involves passing the substance through a column packed with at least the
modified
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_'j_
carbonaceous material as the stationary phase and the mobile phase. The type
of
chromatography that can be accomplished by 'the present invention includes,
but is not
limited to, size exclusion chromatography and amity chromatography (wherein
the affinity
between the modified carbonaceous material and the different chemical species
in the
mixture is different such that separation occurs at different rates). Another
type of
chromatography that can be accomplished by the present invention is adsorption-
desorption
chromatography, reverse phase chromatography, ion exchange chromatography,
hydrophobic
interaction chromatography, chiral chromatography, capillary liquid
chromatography,
supercritical fluid chromatography, or electrochromatography.
Chromatographic separation of proteins and other biomolecules can also be
accomplished by the present invention. An example of such a bioseparation
would involve
the use of a stationary phase wherein polyols or polyethylene glycol compounds
are attached
on the carbonaceous material. Another example of a bioseparation would involve
the use of a
stationary phase wherein benzoic acid or benzenesulfonic groups are attached
to the surface
of the carbonaceous material.
Typically, a chromatographic system contains a mobile phase, a stationary
phase, a
pumping system, and a detector. Generally, the stationary phase contains
insoluble particles
which are preferably spherical and preferably range in size from about 1
micron to about 500
microns, and most preferably 2 to 5 microns, for analytical chromatography and
10 to 40
3 0 microns for preparative chromatographic applications. These particles have
a surface area
ranging from about 1 to about 500 m2/g. preferably 50 to 200 m2/g, and a mean
pore
diameter ranging from about 20 to about 20,000 Angstrom, preferably 60 to 1000
Angstrom.
The choice of these particles depends on the physical, chemical, and/or
biological
interactions that need to be exploited by the separation. Conventional
stationary phases, such
2 5 as silica, agarose, polystyrene-divinylbenzene, polyacrylamide, dextrin,
hydroxyapatite,
cross-linked polysaccharides, and polymethacrylates are functionalized with
certain groups in
order to accomplish the selective separation of particular chemical compounds
from a
mixture. The precise functional groups that accomplish this desired
specification are set
forth, for instance, in Garcia, Bonen et al., "Biosepas°ation Process
Science," Blackwell
30 Science (1999), incorporated in its entirety by reference herein. In
preferred instances, the
functional groups described in Garcia et al. axe the organic groups attached
to the
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_g_
carbonaceous materials based on the present invention or are part of the
organic group
attached to the carbonaceous materials (e.g., the functional groups of Garcia
et al. attached to
the carbonaceous material through at least one aromatic group or alkyl group,
wherein the
aromatic group or alkyl group are preferably directly attached to the
carbonaceous material).
Another form of separation is electrophoresis which uses an applied electric
field to
produce directed movement of charged molecules. The process is similar to
chromatographic
methods in that a fixed barrier phase or stationary phase is used to
facilitate separation. In the
present invention, electrophoresis can be accomplished by using a stationary
phase which
contains the modified carbonaceous material of the present invention.
Similarly, magnetic separations, such as magnetic bioseparations, can be
accomplished using the modified magnetic carbonaceous materials of the present
invention
as the stationary phase.
In addition, membrane separations, such as reverse osmosis, can be
accomplished by
forming the membrane such that it contains modified carbonaceous materials.
The
membrane can be formed by dispersing the modified carbonaceous material in a
polymer and
casting the polymer mixture to form a membrane. Another way to make the
membrane is to
form a conventional membrane and then surface modify the membrane to attach
organic
groups onto the membrane. Membranes can be used in a variety of separation
techniques,
including protein separations and/or metal removal.
2 0 Generally, any separation technique which involves the use of a stationary
phase can
be improved by the present invention. In particular, the stationary phase can
be or can contain
the modified carbonaceous material of the present invention. Upon knowing the
desired
chemical compound or species to be separated, the modified carbonaceous
material can be
tailored to be selective to the targeted chemical species by attaching an
organic group or
~ 5 organic groups onto the carbonaceous material to suit the separation
needed. Since many
functional groups are known to cause particular selectivity in separations,
these groups can
be attached onto the carbonaceous material to form the modified carbonaceous
material of
the present invention and achieve the desired selectivity for separation
processes.
In one embodiment, an adsorbent composition of the present invention contains
a
3 0 modified carbonaceous material capable of adsorbing an adsorbate wherein
at least one
organic group is attached to the carbonaceous material.
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The carbonaceous material capable of adsorbing an adsorbate includes, but is
not
limited to, activated carbon, carbon black, graphite, or other carbonaceous
material obtained
by the pyrolysis of cellulosic, fuel oil, polymeric, or other precursors.
Additional examples,
include but are not limited to, carbon fibers, carbon cloth, vitreous carbon,
carbon aerogels,
pyrolized ion exchange resins, pyrolized polymer resins, mesoporous carbon
microbeads,
pelleted carbon powder, nanotubes, buckyballs, silicon-treated carbon black,
silica-coated
carbon black, metal-treated carbon black, densified carbon black, carbon clad
silica, alumina,
and ceria particles, and combinations thereof or activated versions thereof.
The carbonaceous
material can also be a waste product or by-product of carbonaceous material
obtained by
pyrolysis, including carbonized polymeric particles (e.g., polydivinylbenzene
based
chromatographic particles, or sulfonated polydivinylbenzene/polystyrene
particles).
Preferably, the carbonaceous material is ~ activated carbon or carbon black
capable of
adsorbing an adsorbate. Commercial examples of carbon black include, but are
not limited
to, Black Pearls0 2000 carbon black, Black Pearls~ 430 carbon black, Black
Pearls0 900
carbon black, and Black Pearls~ 120 carbon black, all available from Cabot
Corporation.
Commercial examples of activated carbon include Darco 551, available from
Norit;
Sorbonorit 3, available from Norit; Ambersorb adsorbent (available from Rohm
and Haas);
Hypercarb carbon particle (available from ThermoHyperSil); TosoHaas carbon
materials;
and BPL activated carbon from Calgon. The carbonaceous material modified by
the
2 0 procedures described herein may be a microporous or mesoporous activated
carbon in
granular or pellet form; a carbon black of different structures in fluffy or
pelleted form; or
any other carbonaceous material whose applicability to this invention is
apparent to those
skilled in the art, such as carbon fibers or carbon cloth. The choice of
carbonaceous material
used eventually depends on a variety of different factors, including the
application for which
2 5 it is intended. Each of these types of carbonaceous material has the
ability to adsorb at least
one adsorbate. A variety of BET surface areas, micropore volumes, and total
pore volumes
are available depending on the desired end use of the carbonaceous material.
Carbonaceous materials include, but are not limited to, material obtained by
the
compaction of small carbon particles and other finely divided forms of carbon
as long as the
30 carbon has the ability to adsorb at least one adsorbate and is capable of
being chemically
modified in accordance with the present invention.
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Also, for purposes of the present invention, the carbonaceous material can be
an
aggregate comprising a carbon phase and a silicon-containing species phase. A
description of
this aggregate as well as means of making this aggregate is described in PCT
Publication No.
WO 96/37547 and WO 98/47971 as well as U.S. Patent Nos. 5,830,930; 5,869,550;
5,877,238; 5,919,841; 5,948,835; and 5,977,213. All of these patents and
publications are
hereby incorporated in their entireties herein by reference.
The carbonaceous material for purposes of the present invention, can also be
an
aggregate comprising a carbon phase and metal-containing species phase where
the metal-
containing species phase can be a variety of different metals such as
magnesium, calcium,
titanium, vanadium, cobalt, nickel, zirconium, tin, antimony, chromium,
neodymium, lead,
tellurium, barium, cesium, iron, molybdenum, aluminum, and zinc, and mixtures
thereof.
The aggregate comprising the carbon phase and a metal-containing species phase
is
described in U.S. Patent No. 6,017,980, also hereby incorporated in its
entirety herein by
reference.
Also, for purposes. of the present invention, the carbonaceous material
includes a
silica-coated carbon black, such as that described in U.S. Patent No.
5,916,934 and PCT
Publication No. WO 96/37547, published November 28, 1996, also hereby
incorporated in
their entirety herein by reference.
The carbonaceous material described above is then modified by the attachment
of an
2 0 organic group to the carbonaceous material. Preferred processes for
attaching an organic
group to a carbonaceous material and examples or organic groups are described
in detail in
U.S. Patent Nos.5,554,739; 5,559,169; 5,571,311; 5,575,845; 5,630,868;
5,672,198;
5,698,016; 5,837,045; 5,922, I 18; 5,968,243; 6,042,643; 5,900,029; 5,955,232;
5,895,522;
5,885,335; 5,851,280; 5,803,959; 5,713,988; and 5,707,432; and International
Patent
Publication Nos. WO 97/47691; WO 99/23174; WO 99/31175; WO 99/51690; WO
99/63007; and WO 00/22051; all incorporated in their entirety by reference
herein. These
processes can be preferably used in preparing the modified carbon adsorbents
of the present
invention and permit the attachment of an organic group to the carbonaceous
material via a
chemical reaction. As indicated. above, the organic group attached to the
carbonaceous
3 0 material is one preferably capable of increasing the adsorption capacity
and/or selectivity of
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the carbonaceous material and/or enhancing the resolution of solute peaks in
chromatographic separations.
As indicated above, once the desired separation technique is chosen and the
particular
chemical species preferably known, a particular functional group or multiple
functional
groups can be chosen to be attached onto the carbonaceous material in order to
accomplish
the selectivity needed to conduct the separation process. For instance, as set
forth in Garcia et
al., heparin is used in the separation of lipoproteins, accordingly, heparin
can be attached
onto carbonaceous material in order to accomplish the desired separation.
Similarly, when
cationic exchange processes are needed, a sulfonic acid, for instance, can be
attached on a
carbonaceous material and when anionic exchanges are needed, a quaternary
amine can be
attached onto the carbonaceous material. Thus, with the present invention, and
the
knowledge possessed by one skilled in the art, separation techniques can be
conducted using
modified carbonaceous material to achieve the selectivity desired.
Thus, the present invention provides a carbonaceous material which is
resistant to
corrosion, swelling, andlor extreme temperatures and pressures, but also
provides the desired
selectivity. In essence, the present invention gives the separation field the
best of both
worlds, namely, selectivity combined with a resilient stationary phase without
any losses in
the e~ciency of separation.
A preferred process for attaching an organic group to the carbonaceous
materials
2 0 involves the reaction of at least one diazonium salt with a carbonaceous
material in the
absence of an externally applied current sufficient to reduce the diazonium
salt. That is, the
reaction between the diazonium salt and the carbonaceous material proceeds
without an
external source of electrons sufficient to reduce the diazonium salt. Mixtures
of different
diazonium salts may be used. This process can be carried out under a variety
of reaction
2 5 conditions and in any type of reaction medium, including both erotic and
aprotic~ solvent
systems or slurries.
In another preferred process, at least one diazonium salt reacts with a
carbonaceous
material in a erotic reaction medium. Mixtures of different diazonium salts
may be used in
this process. This process can also be carried out under a variety of reaction
conditions.
30 Preferably, in both processes, the diazonium salt is formed in situ. If
desired, in
either, process, the modified carbonaceous material can be isolated and dried
by means
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known in the art. Furthermore, the modified carbonaceous material can be
treated to remove
impurities by known techniques. The various preferred embodiments of these
processes are
discussed below.
The processes can be carried out under a wide variety of conditions and in
general are
not limited by any particular condition. The reaction conditions must be such
that the
particular diazonium salt is sufficiently stable to allow it to react with the
carbonaceous
material. Thus, the processes can be carried out under reaction conditions
where the
diazonium salt is short lived. The reaction between the diazonium salt and the
carbonaceous
material occurs, for example, over a wide range of pH and temperature. The
processes can
be carried out at acidic, neutral, and basic pH. Preferably, the pH ranges
from about 1 to 9.
The reaction temperature may preferably range from O~C to 1 OO~C.
Diazonium salts, as known in the art, may be formed for example by the
reaction of
primary amines with aqueous solutions of nitrous acid. A general discussion of
diazonium
salts and methods for their preparation is found in Morrison and Boyd, Organic
C'.hemi~trT,
5th Ed., pp. 973-983, (Allyn and Bacon, Inc. 1987) and March, Advanced Org ni
(':hemis ry Reacti~n~, Mechanisms and Strapre~, 4th Ed., (Whey, 1992).
According to
this invention, a diazonium salt is an organic compound having one or more
diazonium
groups.
The diazonium salt may be prepared prior to reaction with the carbonaceous
material
2 0 or, more preferably, generated in situ using techniques known in the art.
In situ generation
also allows the use of unstable diazonium salts such as alkyl diazonium salts
and avoids
unnecessary handling or manipulation of the diazonium salt. In particularly
preferred
processes, both the nitrous acid and the diazonium salt are generated in situ.
A diazonium salt, as is known in the art, may be generated by reacting a
primary
amine, a nitrite and an acid. The nitrite may be any metal nitrite, preferably
lithium nitrite,
sodium nitrite, potassium nitrite, or zinc nitrite, or any organic nitrite
such as for example
isoamylnitrite or ethylnitrite. The acid may be any acid, inorganic or
organic, which is
effective in the generation of the diazonium salt. Preferred acids include
nitric acid, HN03,
hydrochloric acid, HCI, and sulfuric acid, H2SO4.
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The diazonium salt may also be generated by reacting the primary amine with an
aqueous solution of nitrogen dioxide. The aqueous solution of nitrogen
dioxide, NOz/HzO,
provides the nitrous acid needed to generate the diazonium salt.
Generating the diazonium salt in the presence of excess HCI may be less
preferred
than other alternatives because HCl is corrosive to stainless steel.
Generation of the
diazonium salt with NOz/Hz0 has the additional advantage of being less
corrosive to
stainless steel or other metals commonly used for reaction vessels. Generation
using
HzSOa/NaNOz or HN03/NaNOz are also relatively non-corrosive.
In general, generating a diazonium salt from a primary amine, a nitrite, and
an acid
requires two equivalents of acid based on the amount of amine used. In an in
situ process,
the diazonium salt can be generated using one equivalent of the acid. When the
primary
amine contains a strong acid group, adding a separate acid may not be
necessary. The acid
group or groups of the primary amine can supply one or both of the needed
equivalents of
acid. When the primary amine contains a strong acid group, preferably either
no additional
acid or up to one equivalent of additional acid is added to a process of the
invention to
generate the diazonium salt in situ. A slight excess of additional acid may be
used. One
example of such a primary amine is para-aminobenzenesulfonic acid (sulfanilic
acid).
In general, diazonium salts are thermally unstable. They are typically
prepared in
solution at low temperatures, such as 0-S~C, and used without isolation of the
salt. Heating
2 0 solutions of some diazonium salts may liberate nitrogen and form either
the corresponding
alcohols in acidic media or the organic free radicals in basic media.
However, the diazonium salt need only be sufficiently stable to allow reaction
with
the carbonaceous material. Thus, the processes can be carried out with some
diazonium salts
otherwise considered to be unstable and subject to decomposition. Some
decomposition
2 5 processes may compete with the reaction between the carbonaceous material
and the
diazonium salt and may reduce the total number of organic groups attached to
the
carbonaceous material. Further, the reaction may be carried out at elevated
temperatures
where many diazonium salts may be susceptible to decomposition. Elevated
temperatures
may also advantageously increase the solubility of the diazonium salt in the
reaction medium
3 0 and improve its handling during the process. However, elevated
temperatures may result in
some loss of the diazonium salt due to other decomposition processes.
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Reagents can be added to form the diazonium salt in situ, to a suspension of
carbonaceous material in the reaction medium, f~r example, water. Thus, a
carbonaceous
material suspension to be used may already contain one or more reagents to
generate the
diazonium salt and the process accomplished by adding the remaining reagents.
Reactions to form a diazonium salt are compatible with a large variety of
functional
groups commonly found on organic compounds. Thus, only the availability of a
diazonium
salt for reaction with a carbonaceous material limits the processes of the
invention.
The processes can be carried out in any reaction medium which allows the
reaction
between the diazonium .salt and the carbonaceous material to proceed.
Preferably, the
reaction medium is a solvent-based system. The solvent may be a erotic
solvent, an aprotic
solvent, or a mixture of solvents. Protic solvents are solvents, like water or
methanol,
containing a hydrogen attached to an oxygen or nitrogen and thus are
sufficiently acidic to
form hydrogen bonds. Aprotic solvents are solvents which do not contain an
acidic
hydrogen as defined above. Aprotic solvents include, for example, solvents
such as hexanes,
tetrahydrofuran (THF), acetonitrile, and benzonitrile. For a discussion of
erotic and aprotic
solvents see Morrison and Boyd, organic C'hPmi~trT, 5th Ed., pp. 228-231,
(Allyn and
Bacon, Inc. 1987). -
The processes are preferably carried out in a erotic reaction medium, that is,
in a
erotic solvent alone or a mixture of solvents which 1 contains at Least one
erotic solvent.
2 0 Preferred erotic media include, but are not limited to water, aqueous
media containing water
and other solvents, alcohols, and any media containing an alcohol, or mixtures
of such
media.
The reaction between a diazonium salt and a carbonaceous material can take
place
with any type of carbonaceous material, for example, in finely divided state
or pelleted form.
2 5 In one embodiment designed to reduce production costs, the reaction occurs
during a
process for forming carbonaceous material pellets. For example, a carbonaceous
material
product of the invention can be prepared in a dry drum by spraying a solution
or slurry of a
diazonium salt onto a carbonaceous material. Alternatively, the carbonaceous
material
product can be prepared by pelIetizing a carbonaceous material in the presence
of a solvent
3 0 system, such as water, containing the diazonium salt or the reagents to
generate the
diazonium salt, in situ. Aqueous solvent systems are preferred.
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In general, the processes produce inorganic by-products, such as salts. In
some end
uses, such as those discussed below, these by-products may be undesirable.
Several possible
ways to produce a carbonaceous material product without unwanted inorganic by-
products or
salts are as follows:
First, the diazonium salt can be purified before use by removing the unwanted
inorganic by-product using means known in the art. Second, the diazonium salt
can be
generated with the use of an organic nitrite as the diazotization agent
yielding the
corresponding alcohol rather than an inorganic salt. Third, when the diazonium
salt is
generated from an amine having an acid group and aqueous NOz, no inorganic
salts are
formed. Other ways may be known to those of skill in the art.
In addition to the inorganic by-products, the process may also produce organic
by-products. They can be removed, for example, by extraction with organic
solvents. Other
ways of obtaining products without unwarranted organic by-products may be
known to those
of skill in the art, and include washing or removal of ions by reverse
osmosis.
The reaction between a diazonium salt and a carbonaceous material forms a
carbonaceous material product having an organic group attached to the
carbonaceous
material. The diazonium salt may contain the organic group to be attached to
the
carbonaceous material. It may be possible to produce the carbonaceous material
products of
this invention by other means known to those skilled in the art.
2 0 The organic group may be an aliphatic group, a cyclic organic group, or an
organic
compound having an aliphatic portion and a cyclic portion. As discussed above,
the
diazonium salt employed can be derived from a primary amine having one of
these groups
and being capable of forming, even transiently, a diazonium salt. The organic
group may be
substituted or unsubstituted, branched or unbranched. Aliphatic groups
include, for example,
2 5 groups derived from alkanes, alkenes, alcohols, ethers, aldehydes,
ketones, carboxylic acids,
and carbohydrates. Cyclic organic groups include, but are not limited to,
alicyclic
hydrocarbon groups (for example, cycloalkyls, cycloalkenyls), heterocyclic
hydrocarbon
groups (for example, pyrrolidinyl, pyrrolinyl, piperidinyl, morpholinyl, and
the like), aryl
groups (for example, phenyl, naphthyl, anthracenyl, and the like), and
heteroaryl groups
3 0 (imidazolyl, pyrazolyl, pyridinyl, thienyl, thiazolyl, furyl, indolyl, and
the like). As the steric
hindrance of a substituted organic group increases, the number of organic
groups attached to
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the carbonaceous material from the reaction between the diazonium salt and the
carbonaceous material may be diminished.
When the organic group is substituted, it may contain any functional group
compatible with the formation of a diazonium salt. Functional groups include,
but are not
limited to, R, OR, COR, COOR, ODOR, carboxylate salts such as COOLi, COONa,
COOK,
GOONR4+, halogen, CN, NRz, S03H, sulfonate salts such as S03Li, SOsNa, S03K,
SO3T1R4+, OSOsH, OS03 salts, NR(COR), CONRz, NOz, P03Hz, phosphonate salts
such as
POsHNa and P03Naz, phosphate salts such as OPOsHNa and OPOsNaz, N=NR, NR3~X-,
PR3+X-, SkR, SS03H, SS03 salts, SOzNRR', SOaSR, SNRR', SNQ, SOaNQ, COzNQ, S-
(1,4-piperazinediyl)-SR, 2-(1,3-dithianyl) 2-(1,3-dithiolanyl), SOR, and SOZR.
R and R',
which can be the same or different, are independently hydrogen, branched or
unbranched C~-
Czo substituted or unsubstituted, saturated or unsaturated hydrocarbon, e.g.,
alkyl, alkenyl,
alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted
heteroaryl, substituted
or unsubstituted alkylaryl, or substituted or unsubstituted arylalkyl. The
integer k ranges
from 1-8 and preferably from 2-4. The anion X- is a halide or an anion derived
from a
mineral or organic acid. Q is (CHz)W, (CHz)a0(CHz)Z, (CHz)~NR(CHz)Z, or
(CHz)~S(CHz)Z,
where w is an integer from 2 to 6 and x and z are integers from 1 to 6. In the
above formula,
specific examples of R and R' are NHz-C6Ha-, CHzCHz-C6Ha-NHz, CHz-C6H~-NHz,
and
C6Hs.
Another example of an organic group is an aromatic group of the formula AyAr-,
which corresponds to a primary amine of the formula AyArNHz. In this formula,
the
variables have the following meanings: Ar is an aromatic radical such as an
aryl or heteroaryl
group. Ar can be selected from the group consisting of phenyl, naphthyl,
anthracenyl,
phenanthrenyl, biphenyl, pyridinyl, benzothiadiazolyl, and benzothiazolyl; A
is a substituent
2 5 on the aromatic radical independently selected from a preferred functional
group described
above or A is a linear, branched or cyclic hydrocarbon radical (preferably
containing 1 to 20
carbon atoms), unsubstituted or substituted with one or more of those
functional groups; and
y is an integer from 1 to the total number of -CH radicals in the aromatic
radical. For
instance, y is an integer from 1 to 5 when Ar is phenyl, 1 to 7 when Ar is
naphthyl, 1 to 9
3 0 when Ar is anthracenyl, phenanthrenyl, or biphenyl, or 1 to 4 when Ar is
pyridinyl.
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Another set of organic groups which may be attached to the carbonaceous
material
are organic groups substituted with an ionic or an ionizable group as a
functional group. An
ionizable group is one which is capable of forming an ionic group in the
medium of use. The
ionic group may be an anionic group or a cationic group and the ionizable
group may form
an anion or a cation.
Ionizable functional groups forming anions include, for example, acidic groups
or
salts of acidic groups. The organic groups, therefore, include groups derived
from organic
acids. Preferably, when it contains an ionizable group forming an anion, such
an organic
group has a) an aromatic group or a C~-C~z alkyl group and b) at least one
acidic group
having a pKa of less than I l, or at least one salt of an acidic group having
a pKa of less than
11, or a mixture of at least one acidic group having a pKa of less than 11 and
at least one salt
of an acidic group having a pKa of less than 11. The pICa of the acidic group
refers to the
pKa of the organic group as a whole, not just the acidic substituent. More
preferably, the
pKa is less than 10 and most preferably less than 9. Preferably, the aromatic
group or the C~-
C~z alkyl group of the organic group is directly attached to the carbonaceous
material. The
aromatic group may be further substituted or unsubstituted, for example, with
alkyl groups.
The organic group can be a phenyl or a naphthyl group and the acidic group is
a sulfonic acid
group, a sulfinic acid group, a phosphonic acid group, or a carboxylic acid
group. The
organic group may also contain one or more asymmetric centers. Examples of
these acidic
2 0 groups and their salts are discussed above. The organic group can be a
substituted or
unsubstituted sulfophenyl group or a salt thereof; a substituted or
unsubstituted
(polysulfo)phenyl group or a salt thereof; a substituted or unsubstituted
sulfonaphthyl group
or a salt thereof; or a substituted or unsubstituted (polysulfo)naphthyl group
or a salt thereof.
An example of a substituted sulfophenyl group is hydroxysulfophenyl group or a
salt
~ 5 thereof.
Specific organic groups having an ionizable functional group forming an anion
(and
their corresponding primary amines for use in a process according to the
invention) are p-
sulfophenyl (p-sulfanilic acid), 4-hydroxy-3-sulfophenyl (2-hydroxy-5-amino-
benzenesulfonic acid), and 2-sulfoethyl (2-aminoethanesulfonic acid).
3 0 Amines represent examples of ionizable functional groups that form
cationic groups.
For example, amines may be protonated to form ammonium groups in acidic media.
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Preferably, an organic group having an amine substituent has a pKb of less
than 5..
Quaternary ammonium groups (-NR3+) and quaternary phosphonium groups (-PRs+)
also
represent examples of cationic groups. The organic group can contain an
aromatic group
such as a phenyl or a naphthyl group and a quaternary ammonium or a quaternary
phosphonium group. The aromatic group is preferably directly attached to the
carbonaceous
material. Quaternized cyclic amines, and even quaternized aromatic amines, can
also be
used as the organic group. Thus, N-substituted pyridinium compounds, such as N-
methyl
pyridyl, can be used in this regard. Examples of organic groups include, but
are not limited
t0, (CsHaN)CaHs~X , C6Ha(NCsHs)+X , C6H4COCHaN(CH3)s+X , CsH4COCHz(NCsHs)+X_,
(CsHaN)CH3+X-, and
C6H4CHzN(CH3)3+X , where X- is a halide or an anion derived from a mineral or
organic
acid.
Aromatic sulfides encompass another group of organic groups. These aromatic
sulfides can be represented by the formulas Ar(CHz)qS~;(CH2)rAr' or A-
(CHz)qS,c(CHz)rAr"
1.5 wherein Ar and Ar' are independently substituted or unsubstituted arylene
or heteroarylene
groups, Ar" is an aryl or heteroaryl group, k is 1 to 8 and q and r are 0-4.
Substituted aryl
groups would include substituted alkylaryl groups. Examples of arylene groups
include
phenylene groups, particularly p-phenylene groups, , or benzothiazolylene
groups. Aryl
groups include phenyl, naphthyl and benzothiazolyl. The number of sulfurs
present, defined
2 0 by k preferably ranges from 2 to 4. Examples of carbonaceous material
products are those
having an attached aromatic sulfide organic group of the formula -(C6H4)-Sk-
(C6H4)-, where
k is an integer from 1 to 8, and more preferably where k ranges from 2 to 4.
Other examples
of aromatic sulfide groups are bis-para-(C6Ha)-Sz-(C6Ha)- and para-(C6Ha)-Sz-
(CsHs). The
diazonium salts of these aromatic sulfide groups may be conveniently prepared
from their
25 corresponding primary amines, HzN-Ar-S~-Ar'-NHz or HzN-Ar-S~;-Ar". Groups
include
dithiodi-4,1-phenylene, tetrathiodi-4,1-phenylene, phenyldithiophenylene,
dithiodi-4,1-(3-
chlorophenylene), -(4-CsH4)-S-S-(2-C~H4NS), -(4-C6H~)-S-S-(4-CsH4)-OH, -6-(2-
C~H3NS)-
SH, -(4-CsHa)-CHzCHz-S-S-CHZCHz-(4-C6H4)-, -(4-CsHø)-CHzCHz-S-S-S-CHzCHz-(4-
C6Ha)-, -(2-C6Hd)-S-S-(2-C6Ha)-, -(3-CsHa)-S-S-(3-C6Ha)-, -6-(C6H3N2S), -6-(2-
C~H3NS)-S_
3 0 NRR' where RR' is -CHaCHaOCHzCHz-, -(4-CsH4)-S-S-S-S-(4-C6H4)-, -(4-C6Ha)-
CH=CHz,
-(4-CsHa)-S-SO3H, -(4-C6H4)-SOZNH-(4-CsHa)-S-S-(4-C6Ha)-NHSOz-(4-C6Ha)-, -6-(2-
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C~H3NS)-S-S-2-(6-C~H3NS)-, -(4-C6Ha)-S-CHz-(4-C6Ha)-, -(4-C6Ha)-SOz-S-(4-CsHa)-
, -(4
CsHa)-CHz-S-CHz-(4-C6Ha)-, -(3-C6Ha)-CHz-S-CHz-(3-C6Ha)-, -(4-CsHa)-CHz-S-S-
CHz-(4
CsHa)-, -(3-C6H4)-CHz-S-S-CHz-(3-C6Ha)-, -(4-C6Ha)-S-NRR', where RR' is
CHzCHaOCHaCHz-, -(4-C6Ha)-SOzNH-CHzCHz-S-S-CHaCHz-NHSOz-(4-CsHø)-, -(4
C6Ha)-2-(1,3-dithianyl), and -(4-C6Ha)-S-(1,4-piperizinediyl)-S-(4-C6Ha)-.
Another set of organic groups which may be attached to the carbonaceous
material
are organic groups having an aminophenyl, such as (C6Ha)-NHz, (C6Ha)-CHz-
(C6Ha)-NHz,
(C6Ha)-SOz-(CsHa)-NHz.
Preferably, the organic group is a C~-Coo alkyl group (more preferably a C~-
C~z alkyl
l0 group), an aromatic group, or other organic group, monomeric group, or
polymeric group,
each optionally having a functional group or ionic or ionizable group. More
preferably, these
groups are directly attached to the carbonaceous material.
The polymeric group can be any polymeric group capable of being attached to a
carbon product. The polymeric group can be a polyolefin group, a polystyrenic
group, a
polyacrylate group, a polyamide group, a polyester group, or mixtures thereof.
Monomeric
groups are monomeric versions of the polymeric groups.
The organic group can also be an olefin group, a styrenic group, an acrylate
group,
an amide group, an ester, or mixtures thereof. The organic group can also be
an aromatic
group or an alkyl group, either group with an olefin group, a styrenic group,
an acrylate
2 0 group, an amide group, an ester group, or mixtures thereof, wherein
preferably the
aromatic group, or the alkyl group, like a C~-C~z group, is directly attached
to the carbon
product.
The polymeric group can include an aromatic group or an alkyl group, like a C~-
C~z
group, either group with a polyolefin group, a polystyrenic group, a
polyacrylate group, a
~ 5 polyamide group, an polyester group, or mixtures thereof.
The organic group can also comprise an aralkyl group or alkylaryl group, which
is
preferably directly attached to the carbon product. Other examples of organic
groups
include a Ci-Coo alkyl group, and more preferably a Czo-Cso alkyl group.
Examples of other organic groups are organic groups having the following
3 0 formulas (hyphens on one or more ends represents an attachment to a carbon
product or to
another group):
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-Ar-COz(CmHzm+~), where m = 0 to about 20;
-Ar-(CnHzn+~), where n = 1 to about 50;
-Ar-CPHzp Ar-, where p = 1 to about 10;
-Ar-CXs, where X is a halogen atom;
-Ar-O-CXs, where X is a halogen atom;
-Ar-S03-;
-Ar-SOz(CqHz~_1 ), where q = about 2 to about 10;
-Ar-Sz-Ar-NHz;
-Ar-Sz-Ar-;
-ArSOzH;
-Ar-((C"Hzn)COOX)m, where n=0 to 20, m=1 to 3, and X=H, canons, or organic
group; These groups are further activated and/or reacted with such groups as
carbodiimides and further reacted with NHz-terminated functionalization
groups; SOCIz,
or PCIs, or PC15 to be converted to -Ar-(C"Hz")COCI)m groups and further
reacted with
OH-terminated functionalization groups.
-Ar-((C"Hz~)OH)m, where n=0 to 20, m=I to 3; These groups are further
activated
and/or reacted with such groups as tosyl chloride and subsequently reacted
with amino-
terminated ligands; carbonyldiimidazole and subsequently reacted with amino-
terminated
ligands; carbonylchloride terminated ligands; and epoxy terminated ligands.
2 0 -Ar-((CnHzn)NHz)m, where n=0 to 20, m=1 to 3, and its protonated form: -Ar-
((CnHz")NH3X)m, where X is an ion; These groups are further activated and/or
reacted with
such groups as carbodiimide activated carboxyl-terminated ligands;
carbonyldiimidazole
activated hydroxy-terminated ligands; tosyl activated hydroxy-terminated
ligands; vinyl
terminated ligands; alkylhalide terminated ligands; or epoxy terminated
ligands.
2 5 -Ar-((CnHz")CHNH3+COO-)", where n=0 to 20 and m=1 to 3; These groups are
derivatized further by reaction through the carboxylic group by reaction with
NHz or OH
terminated groups or through the amino group by reaction with activated
carboxy-
terminated ligands, activated hydroxy-terminated ligands, vinyl ligands,
alkylhalide
terminated ligands, or epoxy terminated ligands.
3 0 -Ar-((C"Hzn)CH=CHz)m, where n=0 to 20, m=1 to 3 or -Ar-
((CnHz")SOzCH=CHz)m, where n=0 to 20, m=1 to 3. These groups are further
activated
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and/or reacted with such groups as amino-terminated ligands; peroxy-acids to
form
epoxides and subsequently reacted with hydroxy- or amino-terminated ligands;
hydrogen
halides to form -Ar((C"Hzr,)CHzCHaX)", groups and subsequently reacted with
amino-
terminated ligands.
Other reaction schemes can be used to form various groups onto the
carbonaceous
material.
Preferred mixtures of organic groups include the following:
-Ar-SOs and -Ar(CnHzn+~), where n = 1 to about 50;
-Ar-SZ-Ar-NHz and -ArCPHzPAr-, where p = 1 to about 10;
-Ar-Sz-Ar- and -ArCPHzPAr-, where p = 1 to about 10; or
at least two different -Ar-COZ(CmHzm+~), where m = 0 to about 20.
The various organic, monomeric, and polymeric groups described above and below
which are part of the modified carbon product can be unsubstituted or
substituted and can
be branched or linear.
Any one or more of these organic groups, after attachment to the carbonaceous
material which permits adsorption, and preferably an increase in the
adsorption capacity of
the carbonaceous material may be used in the present invention.
Preferably, the organic group attached to the carbonaceous material is an acid
or base
or a salt of an acid or base, and specific examples include phenyl or naphthyl
groups having
~ 0 substituents like sulfonic acid and carboxylic acid. Quaternary ammonium
can also be used.
Most preferred organic groups attached to the carbonaceous material are (CsHø)-
S03T1a~,
(C6Ha)-SOs K+, (C6Ha)-SOs Li+, and the like. Generally, an acid-type organic
group
attachment will be useful in adsorbing basic adsorbates while a base-type
organic group
attachment will be useful in adsorbing acidic adsorbates.
~ 5 Other preferred organic groups which can be used in the present invention
include
amino acids and derivatized amino acids (e.g., phenyl alanine and its
derivatives),
cyclodextrins, immobilized proteins and polyproteins, and the like. Other
organic groups
include, but are not limited to, C6F5- groups and/or trifluoromethyl-phenyl
groups, and bis-
trif(uorophenyl groups, other aromatic groups with fluorine groups, and the
like. These
3 0 organic groups are particularly preferred with respect to the embodiments
of the present
invention relating to chromatography and other separation techniques.
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Other preferred organic groups which are attached onto the carbonaceous
material
include -Ar-(CnHan+~)x group functionalities, wherein n is an integer of from
about I to about
30 and x is an integer of from about I to about 3. These groups are
particularly preferred for
purposes of reverse phase chromatography. Another example of an organic group
is benzene
with a sulfonic group, benzoic groups, isophtalic groups which are
particularly useful for
cationic exchanges and quaternary amine groups which are particularly
preferred for anionic
exchanges.
Organic groups such as cyclodextrins which are directly attached onto the
carbonaceous material or attached through an alkyl group such as C"Han+~ chain
wherein n is
an integer of from about 3 to about 20 and also preferred. Other groups that
can be attached
are optically pure amino acids and derivatized amino acids, immobilized
proteins, and the
like. These types of organic groups are particularly preferred with respect to
chiral
chromatography. .
In addition, polyethyleneglycol (PEG groups) and methoxy-terminated PEG groups
as well as derivatized PEG and MPEG groups can be attached onto the
carbonaceous
material. These types of organic groups are particularly preferred with
respect to affinity
and/or hydrophobic interactions chromatography for the separation, for
instance, of proteins
and polyproteins.
Further examples of organic groups that can be attached, either alone or as an
2 0 additional group, include -Ar-C(CH3)3, -Ar-(CnH2n)CN)m, wherein Ar is an
aromatic
group, n is 0 to 20, and m is I to 3; - Ar-((CnH2n)C(O)N(H)-CxH2x+I)m, wherein
Ar is
an aromatic group, n is 0 to 20, x is 0 to 20 and m is 1 to 3; - Ar-
((CnH2n)N(H)C(O)
CxH2x+I )m, wherein Ar is an aromatic group, n is 0 to 20, x is 0 to 20 and m
is 1 to
3; - Ar-((CnH2n)O-C(O)-N(H)-CxH2x+I )m, wherein Ar is an aromatic group, n is
0 to
2 5 20, x is 0 to 20 and m is I to 3; - Ar-((CnH2n)C(O)N(H)-R)m, wherein Ar is
an aromatic
group, n is 0 to 20, x is 0 to 20 and m is 1 to 3, and R is an organic group; -
Ar-
((CnH2n)N(H)C(O)-R)m, wherein Ar is an aromatic group, n is 0 to 20, x is 0 to
20 and m
is I to 3, and R is an organic group; - Ar-((CnH2n)O-C(O)N(H)-R)m, wherein Ar
is an
aromatic group, n is 0 to 20, x is 0 to 20 and m is 1 to 3, and R is an
organic group.
3 0 In addition, the present invention has the ability to attach organic
groups such that the
organic groups block out microporosity of the carbonaceous material and thus
permits the
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use of microporous materials for separation techniques, such as
chromatography.
Accordingly, the present invention permits the use of microporous materials
that would
otherwise not be chromatographically useful for separations.
In the present invention, more than one type of group can be attached onto the
carbonaceous material. This is especially useful to fill in any gaps on the
surface of the
carbonaceous material not having an attached organic group. The filling in of
such gaps
promotes better selectivity and/or blocks any microporosity that may still
exist in the
carbonaceous material. Typically, the optional second organic group is
attached after the first
primary organic group is attached and the modified carbonaceous material is
preferably
purified is described above by removing any by-products that are produced from
attaching an
organic group onto the carbonaceous material. Afterwards, the second organic
group can
then be attached using the same diazonium salt or other attachment methods.
Typically, the
type of secondary organic groups which are subsequently attached include, but
are not
limited to, organic groups which are shorter in chain length or have less
steric hindrance than
the first organic group attached. For instance, preferred secondary organic
groups include,
but are not limited to, phenyl groups, alkyl phenyl groups having short alkyl
chains (e.g., CI-
C~s), and the like. Particularly preferred groups include, phenyl, methyl-
phenyl, 3,5-
dimethyl-phenyl, 4-isopropyl-phenyl, and 4-tert-butyl-phenyl.
The modified carbonaceous materials of the present invention, especially when
the
2 0 attached organic groups are alkyl phenyl groups, like 4-alkyl-phenyl,
where the length of the
alkyl chain is between 1 and 30, (preferably between 8 or 18), are especially
useful for
reverse phase chromatography applications having surface properties directly
analogous to
octadecyl-modified silica. Additionally, the modified carbonaceous materials
described
above, can have secondary attached groups such as phenyl, methyl-phenyl,
dimethyl-phenyl,
2 5 isopropyl-phenyl, tert-butyl-phenyl, and the like. The carbonaceous
materials of the present
invention will have one or more of the following properties compared to the
conventional
octadecyl silica:
Enhanced pH stability (octadecyl silica is only used in a narrow pH and rarely
above
pH 8). The enhanced carbonaceous materials of the present invention will be
stable at
3 0 al l pH.
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Enhanced temperature stability. These materials can be used at temperatures up
to
250°C, preferably up to 200°C without significant degradation in
performance.
Enhanced resistance to swelling.
Efficiency of separation comparable to silica and much greater than that of
polymeric
chromatographic materials.
The ability to dial-in the surface properties by determining the concentration
of active
and endcapping groups on the surface, which would give the stationary phase
different selectivities.
A combination of different organic groups is possible. For instance, it is
within the
bounds of the present invention to attach more than one type of organic group
to the same
carbonaceous material or use a combination of carbonaceous materials, wherein
some of the
carbonaceous material has been modified with one organic group and another
portion of the
carbonaceous material has been modified with a different organic group.
Varying degrees of
modification are also possible, such as low weight percent or surface area
modification, or a
high weight percent or surface area modification. Also, mixtures of modified
carbonaceous
material and unmodified carbonaceous material can be used. Mixtures of
modified
carbonaceous material with different functionalizations and/or different
levels of treatment
can be used.
Preferably, the modified carbonaceous materials of the present invention,
especially
2 0 when the attached organic group is a phenyl or naphthyl group having
substituents like
sulfonic acid, carboxylic acid, or quaternary ammonium or salts thereof, can
be directly
analogous to polymeric ion exchange resins. These types of carbonaceous
materials of the
present invention can have one or more of the following properties as compared
to
conventional polymeric ion exchangers:
2 5 a) higher temperature stability;
b) greater resistance to swelling; and
c) greater mechanical strength without adversely affecting uptake kinetics.
Furthermore, the modified carbonaceous materials of the present invention,
besides
being used as adsorbents, can also be used in separations ranging from water
treatment to
3 0 metals separation/recovery, ion exchange, catalysis, and the like. An
additional advantage of
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an adsorbent possessing exchangeable groups as described above is that it
confers on the
material the ability to be further surface modified using ion exchange
procedures.
With respect to the adsorbates, any adsorbate capable of being adsorbed by one
or
more of the modified carbonaceous materials of the present invention is
contemplated to be
within the bounds of the present invention. Examples include, but are not
limited to, polar
species such as water, ammonia, mercaptans, sulfur dioxide, and hydrogen
sulfide. By "polar ,
species," it is understood that this is a species whose electronic structure
is not symmetrical.
This includes molecules that possess dipole moments, for example H20 and NH3;
and/or
molecules that possess quadrupole moments, such as COZ and molecules that
possess
unsaturated pi bonds (~), such as alkenes, alkynes, and other organic and
inorganic
compounds with double and triple bonds. Non-polar species such as argon,
oxygen,
methane, and the like can also be adsorbed with the appropriate modified
carbonaceous
materials of the present invention. In view of the description provided in
this application,
those skilled in the art will be able to determine which organic groups need
to be attached to
the carbonaceous materials in order to achieve the most effective adsorption
affinity or
increase in adsorption, depending upon the adsorbate and the adsorption
processes involved.
By developing an adsorbent composition containing a modified carbonaceous
material capable of adsorbing an adsorbate, selectivity for a particular
adsorbate can be
enhanced. Using the proper modified carbonaceoust material, one can
selectively adsorb
2 0 particular species from a multicomponent mixture. In other words,
modifying the
carbonaceous material to create the adsorbent composition of the present
invention can
decrease adsorption affinity for one component in order to maximize the
adsorption affinity
of another component which will maximize separation of the second component
from the
first component. Furthermore, by increasing adsorption of polar species, this
further results
~ 5 in the relatively decreased adsorption of nonpolar species which improves
selectivity.
Further, the carbonaceous material can be modified in such a manner as to add
a hydrophobic
group to "disable" the oxygen functionalities on the surface of the
carbonaceous material to
increase the selectivity for the adsorption of nonpolar species.
The adsorbate can be in a liquid phase or in the gaseous or vapor phase,
depending
3 0 upon the needs and desires of the user. Certain adsorbates can be more
efficiently adsorbed
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from the vapor or gaseous phases than from the liquid phase or vice versa, and
the modified
carbonaceous materials of the present invention are effective in adsorption
from either phase.
One advantage of the present invention is to modify the surface of an
activated
carbon or carbon black adsorbent extensively, without damaging the structure
or making the
adsorbent more friable. For instance, a carbonaceous material can be surface
modified based
on the present invention with exchangeable sodium cations attached to the
surface. This is
very useful from the point of view of substituting different ions to alter the
chemistry of the
surface.
The beneficial effect of using the modified carbonaceous materials of the
present
invention for the purpose of adsorption can be demonstrated by comparing the
adsorption
isotherms of an adsorbate on an unmodified carbonaceous adsorbent and the same
carbonaceous adsorbent modified in accordance with the present invention.
The present invention will be further clarified by the following examples,
which are
intended to be purely exemplary of the present invention.
FXAMPT.FS
The effectiveness of the surface modification of exemplary carbonaceous
material
was determined by comparing the adsorption isotherms of various adsorbates on
the
unmodified carbonaceous materials, with adsorption isotherms on the
carbonaceous
2 0 materials modified in accordance with the present invention. Adsorbates
used were water and
CO2, but other adsorbates could also be used.
Pellets of Black Pearls 430 carbon black and Darco S51 activated carbon from
Norit were surface-modified using the following procedure:
2 5 SnrfarP modification ~f Rla k P arlS tt 43f1 ('arh~n Rla k~
A dispersion of 5 ml of water dilutable phenol-formaldehyde thermosetting
resin
(Schenectady International, Schenectady, NY) in 50 mL of water was mixed with
50 g of
Black Pearls~ 430 carbon black (available from Cabot Corp., Boston, MA). The
mixture
was pressed in 1 g portions using a 0.25 inch stainless steel die at a
pressure of 5000 psi. The
3 0 pellets were heated under flowing argon at ,110°C for one hour and
at 135°C for one hour to
cure the resin. The temperature was then raised under flowing argon at
20°C/min until a
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temperature of 650°C was reached. The temperature was then held at
650°C for three hours
and cooled under flowing argon. The pellets were then crushed into pieces
about 1 mm by
2 mm.
An aqueous solution of 0.81 g of sodium nitrite in about 1 g of water was
added to a
mixture of 16.8 g of the carbon black granules, 2.04 g of sulfanilic acid, and
50 g of water
that was stirring at 84°C. After stirring for two hours, the resulting
material was dried in an
oven at 65°C.
finrfac . m~difi a inn ~fa tivat d arhnm
An aqueous solution of 30.5 g of sodium nitrite in about 100 g of water was
added to
a boiling mixture of 130 g of DARCO S51 activated carbon (available from
Norit), 76.5 g of
sulfanilic acid, and 1300 g of water. After stirring for 15 minutes, the
heating was
discontinued and the mixture was allowed to cool to room temperature with
stirring. The
resulting material was dried overnight in an oven at 50°C.
T~n Rxchan_g~
The surface modified carbons were washed with a large amount of deionized
water
and dried. The material thus obtained was in the sodium form. Further
modification of the
carbon into potassium and lithium forms was carried out by ion exchange using
2M solutions
of ICOH and LiOH, respectively. The ion-exchanged material was washed
thoroughly and
dried. Adsorption experiments were carried out on the washed, dried materials.
The surface areas ofthe unmodified and surface modified carbon materials are
shown
in Table 1 below. Surface areas were calculated from nitrogen (77 K)
adsorption data using
the BET formalism (S.J. Gregg and K.S.W. Sing, in Ads~rnti~n, Surfa , . Ar .a,
and
P~r~," Academic Press, 1982). The adsorption experiments were carried out on
an
ASAP 2000 automated instrument, manufactured by Micromeritics Corp.
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Sample ID BET Surface Pore Volume,
Area, m2/g cm3/g
BP 430 pellets, unmodified 99 0.518
BP 430, modified, washed 92 0.49
Darco S51 694 0.809
Darco S51, modified, washed141.3 0.279
While the activated carbon lost some surface area and pore volume after the
surface
modification treatment, both the carbon black and the activated carbon
underwent an
increase in adsorption capacity per unit surface area as a result of the
surface modification.
The loss of any surface area and pore volume may be mitigated by pre-treating
the
carbonaceous material with immiscible organic solvent, like heptane. The
results from
adsorption of water vapor at 298 I~ on the unmodified and modified material
are shown in
Figure I (carbon black) and Figure 2 (activated carbon). The water adsorption
experiments
were carried out by a batch technique that involved equilibrating the sample
with water vapor
at a constant relative humidity, in a sealed cell. The constant relative
humidities were
attained by using saturated salt solutions, which have known relative
humidities above their
surface.
Both the activated carbon and carbon black contained Na+ ions on the surface
after
the surface modification was carried out. The Na+ ions can be substituted by
other ions using
standard ion exchange procedures (e.g., see lc,n Fx hange, by F. Helfferich,
McGraw-Hill,
1962). The water adsorption isotherms for the surface-modified material with
Nay ions on
2 0 the surface, as wel l as the other ionic forms derived by ion exchange,
are shown in Figures 1
and 2. The adsorption isotherms show the quantity of water vapor adsorbed, per
gram of
adsorbent, as a function of the relative pressure of water vapor. Figures 3
and 4 show the
same data normalized by the BET surface area of the materials. It is clear
that the adsorption
capacities per unit area of the carbon black, Black Pearls~ 430 carbon black
and the Darco
2 5 S51 carbon black, are considerably enhanced by the surface modification
described in this
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invention. In addition, the shape of the water adsorption isotherm is changed
as a result of
the surface modification (concave upward, to linear or convex upward).
The surface modification technique of the present invention may affect the
adsorption
of gases like COz as well, which possesses a quadrupole movement. Figure 5
shows the
adsorption isotherm of COz from the gas phase at 273 I~ .on the same
unmodified and
modified Black Pearls~ 430 carbon black. Adsorption of C02 was carried out on
an
ASAP 2000 automated adsorption system manufactured by Micromeritics Corp. The
figure
shows the quantity of COa adsorbed as a function of the COz pressure. Clearly,
the
adsorption of COZ is enhanced by the carbon surface modification technique
described in this
invention.
The use of carbonaceous material for chromatographic and other biochemical
applications involving contact with proteins has traditionally been hindered
by the non-
specific adsorption of proteins at the carbon surface. Using various types of
conventional
carbonaceous materials as well as carbonaceous materials of the present
invention, several
experiments were conducted to determine the non-specific adsorption of
proteins at the
carbon surface by these various carbonaceous materials including carbonaceous
materials of
the present invention. Black Pearls~ 3700, available from Cabot Corporation,
was
chemically modified by attaching methoxy terminated polyethylene glycol groups
onto the
2 0 carbon black with the use of the diazonium reaction described above. The
polyethylene
groups attached had average molecular weights of 350, 750, and 2000. The
modified carbon
blacks were dispersed in water during their preparation and subsequently
purified by 10
volumes of diafiltration for removal of impurities and reaction byproducts. A
stock solution
of 10 mg/ml of Bovine Serum Albumin (BSA) was prepared and used for all the
experiments
2 5 detailed below. Appropriate amounts of dispersion containing 0.5 g of each
modified carbon
black and 0.5 g of unmodified BP3700 were introduced in separate 20 ml vials.
In each vial,
protein solution and deionized water were introduced so that the total final
weight of the
contents of each vial was approximately 7.5 g, with approximately 7 ml of
liquid. Protein
solutions varied in concentrations between 0 and 4.5 mg/ml. The vials were
vortexed for 2
3 0 hours to intimately mix the protein solution with the carbon black
particles. After 1 week, the
vials were vortexed again, and subsequently 2 ml aliquots were taken and
centrifuged at
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11,000 RPM for the time required to separate the carbon black particles. The
protein
concentrations in the supernatant solutions were measured using the standard
Bradford assay.
The protein concentrations were measured using the standard Bradford Assay as
described in
Analytical Biochernistty, 72, pp. 248-254 (1976}, which is incorporated in its
entirety by
reference herein. As a comparison, Black Pearls~ 3700 which was not modified
was used as
a control. The remaining concentration of BSA in the aqueous solution was
measured after 1
week and the amount of BSA adsorbed by the various carbonaceous materials in
the separate
experiments was plotted. As can be seen in Fig. 6, the modified carbonaceous
material of the
present invention was quite successful in not adsorbing the protein since the
diagonal line in
Fig. 6 represents no adsorption and as can be seen, the chemically modified
carbonaceous
materials of the present invention were quite successful in not adsorbing
significant amounts
of proteins on the surface. However, the untreated or conventional carbon
black adsorbs
significant amounts of the BSA on the carbon surface. Thus, the present
invention, through
the use of organic groups on a carbonaceous material can be quite successful
in promoting
non-specific adsorption of protein at the carbon surface. The conventional
carbon black
adsorbed approximately 0.9 mg/m2 of BSA from a solution after one week while
the
concentration of BSA in the aqueous solution did not change in the presence of
the
carbonaceous materials of the present invention.
Prenaratmn of ~ ta~V~~~ cmrfar Lm~dlfje~ rarhnn n~ar~ ~irnn ' ,.f~' I
I S g of deionized water and I S g of ethanol, 0.83 g of 4-octadecylaniline
and 1.01
g of a 30 wt% nitric acid solution were mixed in a beaker and heated to 50
°C. 10 g of
ZirChrom-Carb particles (provided by ZirChrom Separations, Anoka, MN) were
added to
2 5 the mixture and the temperature was increased to 60 °C. 0.83 g of a
20 wt% solution of
sodium nitrite were added dropwise over 2 minutes. The mixture was left to
react at 60 °C
for I.S hours. After the reaction was complete, the reaction mixture was left
to cool to
room temperature and filtered using Whatman 1 filter paper. The particles were
rinsed
with ethanol, tetrahydrofuran (THF), and a 1 wt% NaOH solution and then
soxhlet
3 0 extracted for I 6 hours in ethanol and 12 hours in THF. The particles SP-I
were
subsequently left to dry. The starting particles ZirChrom-Carb particles had
1.18 wt% C
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and the final SP-1 particles had 3.4 wt%C, indicating surface coverage with
octadecylphenyl groups.
The particles SP-1 prepared in the previous step were mixed in a beaker with
22.5
g of deionized water, 7.5 g of ethanol, 0.22 g of 4-tert-butylaniline, and
0.63 g of a 30 wt%
nitric acid solution and heated to 60 °C. 0.52 g of a 20 wt% solution
of sodium nitrite were
added dropwise over 2 minutes. The mixture was left to react at 60 °C
for 1.5 hours. After
the reaction was complete, the reaction mixture was left to cool to room
temperature and
filtered using Whatman I filter paper. The particles were rinsed with ethanol,
THF, and 1
wt% NaOH solution and extracted in ethanol for 16 hours and THF for 8 hours.
The
particles SP-2 were subsequently left to dry. The final particles had 3.72
wt%C indicating
that tert-butylphenyl groups were attached to the surface.
The particles SP-2 were then slurry packed into a 50 x 4.6 mm HPLC column used
in the subsequent examples of chromatographic separations.
In order to demonstrate the chromatographic use of particles SP-2, the
retention
times of 22 solutes were measured. The solutes were injected in 5 ~1 volumes
into a
2 0 mobile phase consisting of 40 vol% acetonitrile and 60 vol% water held at
30 °C and
flowing at I ml/min. Table 2 contains the retention factors k' for these
solutes for a
column packed with the unmodified ZirChrom-Carb particles and for a column
packed
with particles SP-2. These retention factors were measured using a L1V
detector at 254 nm.
Each solute has a different retention factor, which means that if a mixture of
these solutes
2 5 was injected into the column, they would elute at different times,
enabling their separation.
The effect of surface modification is seen in Table 2. The retention factors
of all
compounds in the column packed with SP-2 particles are different from those in
the
column packed with the unmodified ZirChrom-Carb particles. This indicates that
a unique
and different chromatographic selectivity was accomplished by surface
modification.
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Table 2. Retention factors (k') for 22 solutes obtained with a column packed
with
particles SP-2 compared to those of unmodified ZirChrom-Carb particles .
Solute k' k' (SP-2)
ZirChrom-C18/t-butyl
Carb
N-benz Iformamide0.49 0.222
Benz lalcohol 0.54 0.286
Phenol 0.59 0.236
3- hen I ro 1.19 0.488
anol
-chloro henol 2.49 0.841
Aceto henone 2.06 1.057
Benzonitrile 1.55 1.012
Nitrobenzene 4.76 2.078
Meth lbenzoate 3.75 1.884
Anisole 1.57 1.680
Benzene 0.76 1.454
-chlorotoluene 5.79 6.919
-nitrobenz 1 13.90 4.604
chloride
Toluene 1.70 2.793
Benzo henone 16.91 6.512
Bromobenzene 3.57 5.097
Na thalene 39,48 18.046
Eth lbenzene 2.36 4.526
-x lene 3.85 6.081
-dichlorobenzene8.50 ~ 10.159
!Pro lbenzene 4.73 8.332
Butylbenzene 9 12 15 393
Rxamnl~S
Dodecylphenyl surface modified carbon-clad zirconia particles (SP-3) were
prepared using a similar procedure to that described in Example 3 for,the
preparation of
particles SP-I, using equivalent molar amounts of 4-dodecylaniline instead of
4
octadecylaniline as the treating reagent. t-butyl phenyl endcapped
dodecylphenyl surface
modified carbon-clad zirconia particles (SP-4) were also prepared starting
from particles
SP-3, using a procedure similar to that described in Example 3 for the
preparation of
particles SP-2 from particles SP-1.
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Effect of endcapping on the separation of pharmaceutical molecules
The retention of basic pharmaceutical molecules lidocaine, atenolol, and
labetalol
was measured using HPLC columns packed with ZirChrom-Carb, particles SP-2, SP-
3,
and SP-4. The solutes were injected in 5 p,1 volumes into a mobile phase
consisting of 80
vol% acetonitrile and 20 vol% 20 mM potassium phosphate buffer at pH 10, held
at 30 °C
and flowing at 1 ml/min. The retention factors are compared in Table 3. One
observes that
atenolol and labetalol are very strongly retained on the starting ZirChrom-
Carb HPLC
column, because their retention factors are greater than 30. Surface
modification simply
with a dodecylphenyl group (particles SP-3) decreases the retention factor for
lidocaine,
but does not effect the retention of atenolol and labetalol. It is only after
endcapping with t-
butylphenyl groups (particles SP-4 and SP-2) that the retention of atenolol
and labetalol is
significantly reduced. This reduction in retention indicates that adding the
smaller t-
butylphenyl groups helps improve the chromatographic performance by blocking
access to
the sites on the carbon surface responsible for the strong retention of these
basic
pharmaceutical molecules.
Table 3. Comparison of retention factors for basic pharmaceutical molecules on
various HPLC columns packed with surface modified carbon-clad zirconia
particles.
Solute k' k' (SP-3)k' (SP-4)k' (SP-2)
ZirChrom- C12 Cl2lt-butylCl8lt-butyl
Carb
Lidocaine 19.07 2.33 2.52 5.35
Atenolol >30 >30 1.70 10.12
Labetalol >30 >30 2.03 9.53
A 5 ~,1 mixture of acetone, barbital, metharbital, butethal, hexobarbital,
pentobarbital, and mephobarbital was introduced in a mobile phase consisting
of 80 vol%
acetonitrile, 20 vol% 20 mM Ammonium phosphate buffer at pH 7.0, flowing at I
mllmin
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at 30 °C. The separation of analytes by an HPLC column packed with
particles SP-2 is
shown in Figure 7. The analytes were detected by UV absorption at 2S4 nm.
Fx, an,p~$
In this example the effect of temperature on the separation of 3-phenyl-2-
thiohydantoin (PTH) derivatized aminoacids is used to illustrate the
advantages of
performing chromatographic separations at higher temperatures using the column
containing particles SP-2. A 1 p,1 mixture of PTH derivatives of arginine,
serine, glycine,
alanine, isoaminobutyric acid, aminobutyric acid, valine, and norvaline was
injected into a
mobile phase consisting of 20 vol% Acetonitrile and 80 vol% of a 0.1 %
trifluoroacetic
acid solution at pH 2.0 with a flow rate of 1 ml/min. The separation is shown
at 30 °C and
80 °C in Figure 8. Increasing the temperature by SO °C reduces
the separation time from
greater than 14 minutes to less than 6 minutes, effectively halving the
analysis time.
Senarati~n ef nr~n~tereidal antiinflammat~rT dry
The effect of temperature on the speed of chromatographic separations using
the
packing material SP-2 is also illustrated on this example of the separation of
a mixture of
acetaminophen, ketoprofen, ibuprofen, naproxen, and oxaprofen at 80 and 1S0
°C, which
is shown in Figure 9. At 80 °C, an injection volume of S p,1 was used
in combination with a
2 0 gradient elution, with the mobile phase flowing at 1 ml/min and the
composition
transitioning over 20 minutes from 50 vol°I° to 80 vol%
acetonitrile, and 50 vol% to 20
vol% 40 mM ammonium phosphate, SmM ammonium at pH 2. At a temperature of 1 SO
°C an injection volume of 1 ~I was used with a mobile phase consisting
of 7S vol%
acetonitrile, and 25 vol% 40 mM phosphoric acid at pH 2.3 and a flow rate of
3.0 ml/min.
The separation time dropped from approximately 3 minutes at 80 °C to
less than 1 minute
at 1 SO °C.
The separation of these two molecules is very difficult using traditional
silica based
3 0 stationary phases. However, as .is shown in Figure 10, a column packed
with stationary
phase SP-2 is capable of separating the mixture. An injection volume of S p.1
is used with a
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mobile phase consisting of 25 vol% acetonitrile, 25 vol% tetrahydrofuran, and
50 vol%
water at 30 °C and a flowrate of 1 ml/min.
A column packed with SP-2 was used to separate a mixture of beta-blockers
consisting of labetalol, metoprolol, and alprenolol. A 1 p,1 sample was
injected into a
mobile phase consisting of 45 vol% ACN and 55 vol% 20 mM ammonium phosphate at
pH 11. The mobile phase was heated to 150 °C and flowing at a rate of 3
ml/min. The
detection was by UV at 210 nm. As is shown in Figure 11 the separation was
accomplished in less than 0.5 min.
.(~P=~l.
11 g of deionized water and 4 g of ethanol, 0.17 g (1 mmol) of sulfanilic acid
and
0.21 g of a 30 wt% nitric acid solution (1 mmol) were mixed in a beaker and
heated to 50
°C. 5 g of ZirChrom-Carb particles were added to the mixture and the
temperature was
raised to 65 °C. 0.35 g of a 20 wt% solution of sodium nitrite (I mmol)
were added
dropwise over 2 minutes. The mixture was left to react at 65 °C for 1.5
hours. After the
reaction was complete, the reaction mixture was left to cool to room
temperature and
2 0 filtered using Whatman 1 filter paper. The particles were rinsed with
deionized water,
ethanol, methanol, and a 1 wt% NaOH solution and then extracted using the
Dionex ASE
300 extractor with water, and a 50/50 ethanol-water mixture. The particles SP-
5 were
subsequently left to dry. The starting particles ZirChrom-Carb particles had
0.97 wt% C
and the final SP-5 particles had 1.4 wt% C, indicating the attachment of
benzenesulfonic
2 5 groups.
modified carbon lad sir cnia~article~ y P~-61_
1.96 grams of dinitrobenzoyl-L-phenyl glycine [2, (4-aminophenyl) ethyl] amide
30 were dissolved in a beaker containing a mixture of 31.5 ml tetrahydrofuran
(THF) and 13.5
ml deionized water and heated to 50 °C. 15 grams of Zirchrom-Carb were
added and
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mixed for 5 minutes. 0.591 ml of HCl was diluted with 1 ml of water and added
to the
reaction mixture. 0.256 grams of sodium nitrite was dissolved in 1 ml of water
and added
drop-wise to the reaction mixture. The reagents were mixed for 2 hours at 50
°C. The
particles were filtered by vacuum filtration and washed with THF and Ethanol
and
subsequently extracted for 3 hours with THF. The starting particles ZirChrom-
Carb
particles had 1.68 wt% C and 0.05 wt% N and the final SP-6 particles had 3.1
wt% C and
0.33 wt%N.
(SP-7)
45 g of deionized water and 20 g of ethanol, 0.72 g (5.3 mmol) of 4-
aminophenethylamine and 1.93 g (10.6 mmol) of a 20 wt% hydrochloric acid
solution
were mixed in a beaker and heated to 40 °C. 22 g of ZirChrom-Carb
particles were added
to the mixture and the temperature was increased to 60 °C. 1.82 g (5.3
mmol) of a 20 wt%
solution of sodium nitrite were added dropwise over 2 minutes. The mixture was
left to
react at 60 °C for 1.5 hours. After the reaction was complete, the
reaction mixture was left
to cool to room temperature and filtered using Whatman I filter paper. The
particles were
rinsed with ethanol, THF, and a 1 wt% NaOH solution and then soxhlet extracted
overnight in ethanol. The particles SP-7 were subsequently left to dry. The
starting
2 0 ZirChrom-Carb particles had 1.03 wt% C and the final SP-7 particles had
2.41 wt%C,
indicating surface coverage with phenethylamino groups.
Other embodiments of the present invention will be apparent to those skilled
in the
art from consideration of the specification and practice of the invention
disclosed herein. It
is intended that the specification and examples be considered as exemplary
only, with a true
scope and spirit of the invention being indicated by the following claims and
equivalents
thereof.
