Note: Descriptions are shown in the official language in which they were submitted.
1(~801Z;~
This invention is concerned with a particulate
material useful for analysing a fluid sample, particularly
but not exclusively for use in immunoassays.
This application is a divisional application of
applicant's copending application Serial No, 273,631,
filed March 10, 1977.
It is known to assay biological fluids such as
blood serum or urine to detect and quantify the presence
therein of antibodies (and similar binding proteins),
antigens (and similar substances such as haptens) and
antibody-antigen immune complexes. Such procedures are
broadly called immunoassays. One common technique in
immunoassays is to make use of the binding reaction
which takes place between a limited amount of an antibody
and two antigens, both antigens being capable of binding ;~
with the antibody but being distinguishable, e.g. in
that one antigen carries an identifying label. The
proportion of labelled antigen which binds with the
antibody gives an indication of the amount of unlabelled
antigen present. Thus, if for example a biological
fluid sample containing a specific antigen is mixed
with antibody and an amount of labelled antigen, the
amount of (unlabelled) antigen in the sample can be
determined.
Various labels have been suggested, but the
most successful has been a radioactive label and
immunoassays using radioactive labels are called
"radioimmunoassays" (RIA).
In immunoassay procedures, it is often necessary
to separate the reaction product (e.g. the antibody-
antigen complex) from the raction mixture in order for
example to determine the amount of labelled antigen in
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the product (by direct analysis either of the product
or of the remaining reaction mixture). It has been
suggested in the prior art that in RIA procedures
(in which a separation step is essential), the antibody
be immobilised on a carrier to facilitate subsequent
separation of the reaction product. Thus, in
"Continuous Flow Automated Radioimmunoassay Using
Antibodies Attached to Red Blood Cells", by S. J, Luner,
Analytical Biochemistry, Vol, 65 (1975), pages 355-364,
it is said that red blood cells may be used for the
immobilisation of antibodies in automated RIA techniques
using a continuous-flow system.
In "Magnetic Solid-Phase Radioimmunoassay" by
L. S. Hersh and S. Yaverbaum, Clinica Chemica Acta,
Vol. 63 (1975), pages 69-72, antibody is immobilised on
magnetic particles and the reaction product separated
from the reaction mixture by application of a magnetic
field. This RIA proeedure is carried out in a test
tube reaetor, and the supernatant reaetion mixture is
assayed.
We have now devised a partieulate material `
useful for this purpose, by whieh a series of liquid
samples ean be sueeessively and automatically assayed
by, for exampleS RIA.
The invention relates to a particulate material
for use in the analysis of a liquid sample of known
speeifie gravity. The particulate material comprises
a resgent and one or more magnetic particles in a
matrix of binding material The particulate material
has a controlled specific gravity approaching that of
the liquid sample so as to retard separation of the
particulate material when mixed with the liquid sample.
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The binding material is selected from a group consisting
of: cellulose or a cellulose derivative, a polymer or
synthetic polymeric material, and agarose.
In use a reaction mixture is flowed along a
conduit. The mixture comprises the sample under test
which includes the constituent of interest, i e, the
substance which is to be assayed. In the case, for
example, of biological fluids such as blood serum,
the constituent of interest may, for example, be an
antigen, e.g. a peptide hormone, a steroid hormone, a
drug or a virus (the term "antigen" is intended to
include haptens and other similar substances), an
antibody (which term includes other binding substances),
or an antibody; antigen complex, or a single protein.
The invention is not limited, however, to the assay
of biological fluids.
The reaction mixture also includes, as a
solid phase, magnetically attractable particulate
material which has a reagent bound thereto, This
particulate material may itself be a composite material
made up of, for example, a matrix containing
magnetically attractable material, with the reagent
bound to the particle.
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The magnetically
attractable material may be, for example, iron or
magnetic iron oxides, nickel, cobalt or chromium oxide.
, Suitably, one or more particles of such a material are
¦ 5 embedded in the matrix. The matrix itself may be of a
wide variety of materials including many synthetic and
natural polymeric materials (e.g. cellulose, cellulose ,
derivatives, agarose, organic polymers). The reagent ;~
may be bound directly to the matrix or to another
material within the matrix.
The reagent itself is a substance which takes
part in a reaction in the reaction mixt1lrc. It may
react directly with the constituent of interest in the
sample, or it may react not directly with the sample but
with a second reagent in the mixture. Thus, for example,
the reagent on the particulate matter may be an antibody
which will react directly with an antigen in the sample
under test, or the sample itself may contain an antibody
and the reagent react with an antigen added as the
second reagent. In the latter case, the second reagent
antigen may also react with the antibody in the sample.
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The reagent is bound to the particulate -~
material in such a manner that the reagent is avallable
to react with another substance in the reaction mixture.
Usually, there will be reagent bound to the periphcral
surface of the particulate material, but this is not
essential provided that the reagent is accessible for
reaction. The reagent may thus be wholly within the
matrix but in such case, the matrix will be porous to
the liquid of the reaction mixture.
The nature of the reagent can vary very widely,
depending on the particular analysis to be performed. It
may, for example, be an immunoglobulin, an antigen (e.g.
a virus) or another biological substance. After reaction,
it remains bound (as reaction product) to the particulate
material and is thus separated with the particulate
material from the reaction mixture.
The separation of the particulate material
solid phase from the liquid phase of the reaction mixture
is effected in the conduit using a magnetic trap. The
reaction mixture flows along the conduit into the resion
of a localised magnetic field (the magnetic trap), ~-here-
upon the solid phase is held by the field whilst the
liquid phase flows on.
Preferably, the magnetic field is disposed in
the conduit substantially transversely of the flo~-ing
reaction mixture, but this is not essential. As ~ill be
clear, the strength of the field must be sufficient to
hold the solid phase against the liquid flow.
After the liquid has passed throush the trap,
the solid phase in the trap in the conduit can be washed
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by passing a wash liquid through that portion of the
conduit. The solid phase remains held in the trap but
the particles are exposed to, and washed by, the wash
liquid flowing past. It is a Highly advantageous pre-
ferred feature to be able to
wash the solid phase "on line" and thus the apparatus
preferably comprises means for passing
wash liquid along the conduit.
The wash liquid may be water or any inert
fluid or solution, its purpose being to remove from the
solid phase remaining traces of the reaction mixture
liquid phase. This is particularly important in immuno-
assays, such as RIA, where the solid phase is to be
assayed for the presence of a label, since in such cases
even trace residues of the reaction mixture liquid phase
could lead to incorrect assay results.
The magnetic field is preferably provided by
at least one magnet means actuable to provide magnetic
field in a portion of the conduit. The (or each) magnet
means may be a permanent magnet which is mo~eable to vary
the field from a minimum (when the trap is "de-actuated")
to a maximum "when the trap is "actuated"). We prefer,
however, to use one or more electromagnets. Upon de- -
energisation of the electromagnet, it is preferable to
degauss by providing an alternating current, thus ridding
the electromagnet of residual magnetic field. Solid phase
in the trap will also be demagnetised by this procedure,
thus reducing any tendency to clogging due to magnetic
attraction.
The magnetic trap may consist of a single
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~agnet means, or two or more such means. For many pur-
poses, it is preferred to provide two (or more~ magnetic
traps, spaced apart along the conduit. This enables an
improved washing procedure, for example, to be effected. ~-
Thus, with two traps, the magnet means of each trap are
actuable independently of each other, and the solid phase
is separated from the liquid phase of the reaction
mixture in the first (upstream) trap~ It is washed
whilst it is held in that trap, and then the trap is de-
actuated to release the solid phase into suspension in
flowing wash liquid. The particulate matter is carried
to the second trap (which is energised) and held against
the wash liquid flow. This double wash procedure is ~
particularly effective.
The liquid phase of the reaction mixture passes
through the magnetic trap(s) and flows further along the
conduit. Similarly, after washing, the solid phase is
released from the trap and passes along thc washed con-
duit. Preferably, valving means are provided in the
conduit for directing the separated solid phase or liquid
phase to the analysis means as required. If the solid
phase is to be analysed, the liquid phase of the reaction
mixture can be collected in a receiver or passed to waste~
If the liquid phase is to be measured (possibly together
with wash liquid), the solid phase may be passed to a
receiver, and possibly (after treatment) re-uscd. It
will usually be preferable to assay the solid phase
because it can be automatically washed (as described
above), whereas the liquid phase is likely to be bulky
(with the wash liquid) and not so easily handled or anal~sed.
~080123
The constituent of interest in the sample is
determined by analysis of the separated solid cr liquid
reaction mixture phases. It will be appreciated that
this determination may involve several analytical and/or
calculation steps. Thus, in the case of RIA, analysis of
the solid phase by counting the radioactivity, will reveal
the amount of radioaFtive label in the solid phase. From
this, and standard curves, it will be possible to deter-
mine the amount of constituent of interest in the sample.
It is possible to
effect further reactions on the separated solid or liquid
phase, and to introduce further magnetically attractable
particles for a subsequent separation step. This may be
desirable, for example, when the reaction mixture contains
an enzyme or co-enzyme. In such cases further magnetic
traps may be provided in the conduit downstream of the
trap(s) for effecting the first separation.
The whole or any part of the reaction
mixture may be preformed before it is flowed along the
conduit. It is usually preferred, however, to add one
or more reagents to the flowing sample (or partly formed
mixture) in the conduit. Thus, the apparatus preferably
includes means for introducing the said particulate
material and/or the second reagent into admixture with
the flowing sample (or reaction mixture) in the conduit.
Intermixing of the sample and the reagents will take place
in the conduit as the mixture flows (as is described more
fully hereinafter).
Whilst we have specifically referred above to
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~.
the reagent bound to the particulate material, and to
- the second reagent, it will be understood that there may
also be other reagents present in the reaction mixture.
These other reagents may be added in admixture with the -
particulate material or second reagent, or they may be
pre-mixed with the sample, or they may be added individ-
ually to the flowing sample (or reaction mixture) in the
conduit. The nature of these reagents (if any are used
will be determined by the nature of the assay being per-
formed. The reaction mixture may also contain other sub-
stances such as buffers.
In immunoassays involving binding between, for
example, an antibody and an antigen, the second reagent
will usually carry an identifying label such as a radio-
active atom, a fluorescent group, an enzyme or co-enzyme
or a chemiluminescent material. Thus, for example, when
the biologica] fluid sample is to be assayed for an anti-
gen, the reagent on the particulate material will be an
antibody for binding with the antigen, and the second re-
agent will be an antigen capable of binding with the anti-
body and which also carries a label. In the alternative,
the fluid sample may be assayed for antibody by providing
an antigen on the particulate material and using a labelled
antibody as the second reagent. As will be understood by
those skilled in the art, analysis of the separated solid
phase or liquid phase for the amount of label present will
allow determina'ion of the amount of constituent of interest
in the fluid sample.
The particular analysis to be carried ollt on
the separated solid or liquid phases will depend on the
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'
assay being effected and (where a labelled reagent is
used) on the nature of the label. Thus, the apparatus
may lnclude, for example, means for
measuring the radioactivity, the colour or fluorescence
of the separated phase or i~s enzymic activity. -~
It will be understood that it is not essential
in the method of the invention to use a second or any
reagent other than that bound to the particulate matter.
Thus, the method (and apparatus) can be used, for example,
to separate a particular constituent from a fluid sample
(by selectively binding it to the reagent on the par- ;
ticulate material) and then subsequently assaying the
separated solid phase, In most immunoassay procedures,
however, a second reagent is used (and there may often
be other reagents too).
The method and apparatus may
be used in the known continuous-flow type of procedure
in which individual segments of reaction mixture are
passed along the conduit, separated by an inert fluid
~egment (e.g. air) and, if desired, a wash liquid seg-
ment. This is described in U.S. specification no.
2,797,149 to which reference should be made for further
details. Thus, the apparatus preferably
includes means for passing successive reactio~ mixtures
along said conduit separated from each other by at least
an inert fluid segment of sufficient volume to occlude
said cond~lit and maintain said successive mixtures dis-
crete. The apparatus may also include means for intro-
ducing inert fluid segments into said conduit to sub-
divide li~uid samples or reaction mixtures thercin.
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Further, the apparatus preferably includes means for
providing a wash liquid segment between successive
reaction mixtures flowing in said conduit, each said
mixture being separated from adjacent wash liquid seg-
ments by at least an inert fluid segment.
When the reaction mixture (or sample) is
segmented, and the particulate material and/or the
second reagent is to be added to the flowing segments
in the conduit, then means are provided for introducing
the particulate material (and/or the second reagen~) on
an intermittent basis so that they merge with successi~re
sample segments in the conduit. Preferably, the inter-
mittent introducing means includes means for returning
particulate material not admitted to the conduit, to a
reservoir therefor. Preferably, also, the apparatus
includes means for introducing buffer solution inio said
conduit alternately with said particulato material, so
as (in use) to maintain the flow along said conduit sub-
stantially constant.
It will be appreciated that it is important
that any labelled reagent (or other reagent of critical
importance in the final determination procedllrc) be added
only to the sample or reaction mixture, and not to any t
wash liquid or other segments in the conduit, since other-
wise an incorrect assay may result.
It is convenient, particularly when segmented
flow is used, to provide in the apparatus upstream of
the magnetic trap(s) a sensing means to detect the passage
of a reaction mixture along the conduit and to provide
means for actuating the magnetic trap to trap the
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particles in that reaction mixture, in response to the ~ -
sensing means. Depending on how far upstream of the trap
the sensing means is located, a time delay may be needed
before actuat~on.
The particulate matter will preferably have a
specific gravity close to that of the liquid phase of ~-
the reaction mixture, so that it does not tend to settle
out (nor to float to the top) but rather remains in good
admixture in suspension, Generally, the particulate
matter will have a specific gravity substantially in the
range Gf about 1.4 to 3.2, although values outside this
range can be used.
It will be understood that, in the method ~and
in use of the apparatus) sufficient time must be allowed
after forming the reaction mixture for the desired
reaction(s) to take place, before the solid phase is
separated from the liquid phase To provide this period
(commonly called "incubation"), the conduit may include,
for example, an incubation coil,
In order that the invention may be more fully
understood, one embodiment setting out method and
apparatus for using the particulate material will now be
described, by way of example only, with reference to
the accompanying drawings, in which:
FIGURE 1 is a flow diagram of one form of
apparatus according to the present invention;
FIGURE 2 illustrates the composition of the
fluid stream passed along the system of Figure l;
FIGURE 2A illustrates the two-phase laminar
flow pattern within the fluid samples of Figure 2; and
FIGURES 3A-3C illustrate the operation of the
on-line magnetic traps to effect separation and working
of the solid phase.
Referring now to the drawings, there is shown
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a sampler arrangement 10 for supplying a series of liquid
samples along a compressible pump tube 12. Sampler
arrangement 10 may be of the type shown and described
in U.S. Patent 3, o38,340. Pump tube 12 is incorporated
in a peristaltic-type pump 14, of the type described in
U.S. Patent 2,935,028. (which also controls tubes 38, 40,
3~, 34 l, 30, 30 ~, 32, 36, 52, 57, 84 and 80 as herein-
after described). Probe 15 is controlled to be immersed
alternately in successive sample receptacles 16, and a
wash receptacle 18. As the probe 14 aspirates air
between immersion into successive sample receptacles 16
and wash reservoir lo, the sample stream directed along
pump tube 12 comprises successive samples, each separated
from adjacent samples by air-wash liquid-air segments.
Accordingly, simple integrity is maintained during flow
along the entire system, as hereinafter described. In
addition to sampler 10, a source 20 of antibodies
immobilized on the surface of magnetically attractable
particles in suspension, an associated source 22 of the '
buffer solution, a source 24 of a labelled antigen in
solution, and an associated source 26 of buffer, are pro-
vided. The system is operated such that the solid phase
from source 20, appropriately buffered, and thc lebelled
antigen from source 24, appropriately buffered, are intro-
duced in controlled discrete volumes and proper phases,
to be mixed only with successive samples pumped along
pump tube 12 and conduit 28. To this end, pump 14 com-
prises a plurality of pump tubes, 30, 32, 34 and 36
having respective inlets in fluid communication with
source 20 of the solid phase, source 2~ of the labelled
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antigen and the associated buffer sources 22 and 26.
Also~ pump tubes 38 and 40 are provided for periodically
injecting air bubbles to segment the fluid streams
passed along pump tubes 30 and 34, to provide discrete
segments of uniform concentration of the solid phase and
maintain a constant flow rate through the system when
valves 40 and 42 are operated. Each of the pump tubes
30, 32, 34 and 36 has an associated return conduit 30 ~,
32 l ,34 ~ and 36 ~, respectively, whereby fluid is re-
circulated back to the respective sources 20, 2~, 22
and 26. The outlets of pump tubes 30, 32, 34 and 36
are connected to the inlets of three port-two-position
valves, 42. 44, 40 and 46, respectively. One outlet of
each such valve is connected to the assoclated return
conduit. The remaining outlets of valves 40 and 42,
associated with the solid phase, are multipled and
connected along a mixing coil 48 to conduit 28 a-t junction
A. Also, the remaining outlets of valves 44 and 46 are
multipled and connected along conduit 50 to conduit 28
at junction B. Additionally, the outlet of pump tube 52,
having an inlet exposed to air, is connected to segment
the liquid stream along conduit 50 prior to introduction
into conduit 28. As peristaltic pump 14 opcrates con-
tinuously, air segments are continuously injected via
air pump tubes 38, 40 and 52 so as to achieve both intra-
sample segmentation and intra-wash liquid scgmentation as
hereinafter described, whereby effective internal mixing
of the individual segments of the flowing stream along
conduit 28 is obtained.
Valves 40, 42, 44 and 46 are controlled by a
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pro~rammer 152, which is timed with respect to sampler
10, such that the buffered labelled-antigen stream along
conduit 50, and.the buffered solid phase along mixing
coil 48, are intrQduced in discrete volumes and in pro-
per phase at junctions B and A, respectively, to be inter-
mixed only with each liquid sample along conduit 28.
During passage of the wash liquid segment (intermediate
successive samples) along junction A and also along
junction B, valves 42 and 44 are operated to position I,
to interconnect pump tubes 30 and 32 with conduits 30'
and 32', respectively, and recirculate the liquids being
passed therealong to their sources. Simultaneously,
valves 40 and 46 are operated to position II, to direct
the buffer solution from sources 22 and 26, respecti~ely,
to junctions A and B, to maintain constant flow rates
along conduit 28. At this time, air i9 being pumped
constantly along pump tube 52, wher~by air bubbles are
periodically injected into conduit 50 to segment the
fluid stream therealong and direct it to junction B,-to
ensure proper mixing along coil 55. During passage of a
sample along junctions A and B, programmer 152 operates
valves 42 and 44 momentarily to position II, to introduce
controlled discrete volumes of the buffered solid phase
along mixing coil 48 and of the labelled antig~n sus-
pension along conduit 50 into such sample. A m;~ing
coil 55 is provided along conduit 28 and intcrmediate
junctions A and B, to ensure that tne labelled antigens
are thoroughly mixed and uniformly distributed through-
out each liquid sample segment, prior to introduction
of the solid phase at junction A.
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The successive sample segments, co-mixed
with the solid phase and labelled antigen to form
reaction mixture, are directed along conduit 28 to an
incubation coil 54. The composition of the stream
directed to the incubation 54 is illustrated in Figure
2. Each of the segments~ or aliquots, of samples 51'
S2, etc. include controlled volumes of the solid phase
and labelled antigen; the wash liquid segments (W) are
between successive samples and the successive samples
are themselves segmented by air bubbles introduced along
pump tube 52. In Figure 2A, the labelled antigen and
the solid phase, i.e. antibodies immobilized on ma~net-
ically attractable particles, are distributed throughout
a sample aliquot and are indicated by "-" and "~", res-
pectively. The presence of air segment immediately pre-
ceding and following a liquid segment induces a two-
phase laminar flow pattern, whereby tho liq~lid in such
segment i9 caused to recirculate, as indicated by the
arrows in Figure 2A. Such flow pattern results, primarily,
from the drag imposed on the moving liquid immediately
at the inner surface of conduit 28, and serves to
accelerate the mixing of the various componcnts of the
reaction mixture.
As described, the solid phase comprises mag-
netically attractable particles of controllcd spccific
gravity. Preferably, these particles comprise ~ matrix
having one or more small ferromagnetic particles embedded
therein. For example, the ferromagnetic particles may
be coated with an organic material, e~g~ a polymeric
material, or they may bs silanized, to bind with either
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an antibody or antigen. For example, sui*able coating
techniques have been described in the abo~e-identified
Hersh and Yaverbaum article and, also, in t'The Pro-
perties of Magnetic Supports in Relation to Immobilized
Enzyme Reactions", P.J. Robinson et al, Biotechnology
and Bioengineering,,Vol.XV. (1973) pp. 603-606. The
ratio of the respective volumes of the matrix and the ~-
magnetic particles is chosen so that the resulting
specific gravity approaches that of the liquid phase.
As such, these magnetically attractable particles are
carried along by the two-phase laminar flo~r pattern
induced within each sample aliquot and do not tend to
settle out, either by gravitation or flotation. It
should be appreciated that the specific gravi~y of the
magnetic particles need not be equal to the specific
gravity of the liquid phase, but should be such as to
avoid settling or flotation of the solid phase during
passage through the qystem. The reduced density of such
particles pro~ides for excellent wash characteristics,
whereby there is substantially no contamination between
successive samples. For example, if the particles were
to have a ~pecific gra~ity much higher than that of the
liquid phase, they would tend to settle out and collect
in the cusp defined at the interface between the sample
aliquot and the up-stream air segment along the inner
wall surface of conduit 28. Such settling would sub-
stantially increase the possibility that such particles
could pass under the up-stream air segment, and follow- -
ing liquid and air segments in the flowing stream to
contaminate a following sample. If the spccific gravity
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of the particles is reduced much below that of the
sample, the particles separate out by flotation and may
possibly pass over the following liquid and air segments
to effect contamination. By controlling the specific
gravity of the solid phase, so that it is retained and
carried within the two-phase laminar flow pattern, con-
tamination between successive samples is avoided.
The reaction mixture stream, with the solid
phase constantly circulating within the individual
sample aliquots, is passed through an incubation coil 54
to enable the reaction to proceed. The output of
incubation coil 54 is greatly diluted by buffer directed
along conduit 53 and pump tube 57, to inhibit the reaction
(i.e. quench the reaction) and facilitate washing
of the solid phase by a dilution process. The output
of incubation coil 54, is directed alons conduit 56 to
a wash statiorL~ identified as 58. SUCh wash station pre-
ferably inclucles a firgt magnetic trap 60 and a second
magnetic trap 62, arranged with respect to conduit 56 in
on-line fashion. Each of the magnetic traps 60 and 62
are electromagnetic and arranged to direct magnetic flux
transversely to the path of the sample stream. The
magnetic traps 60 and 62 are operated in particular timed
sequence by programmer 64 controlled by a sample detector
65. Accordingly, sample detector 65 comprises light
source 66 and a detector 68 and is located at the output
of incubation coil 54. Light from source 66 is directed
transversely through conduit 56. l~hen a sample passing
along conduit 56 intercepts such light, at time t of
Figure 2, the reduced output level of a detector 68
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instructs programmer 64 to energize the magnetic traps
60 and 62 concurrently.
l~hen energized, first magnetic trap 60, in
effect, sweeps the solid phase from each of the sample
aliquots comprising, for example, sample S1 as sho~n in
Figure 2. The intensity of the magnetic fields generated
by the first magnetic trap 60 and, also, the second
magnetic trap 62, as hereinafter described, are sufficient
to ensure that passage of intra-sample air bubbles -.~ithin
sample S do not dislodge or carry away any of the solid
phase retained within the wash station 58. Accordingly,
the solid phase in each sample, albeit carried by
individual aliquots, is accumulated along conduit 56
passing through the first magnetic trap 60. Energization
f magnetic trap 62 at time t1 ensures that any solid
phase not swept by magnetic trap 60 is retained. ~agnetic
trap 60 is energized during passage of the entire Yolume
of sample S and, also, during passage of at least a
portion of the following wash liquid segment, i.e. during
time interval t1 - t~ shown in Figure 2. Passage of
such wash liquid segment through wash station 58, while
the solid phase is packed, serves to remove any super-
natant from the magnetic particles. Before the entire
wash liquid segment has been passed, at time t, pro-
grammer 64 de-energizes magnetic trap 60. Accordingly,
the solid phase is caused to be resuspended ~ithin the
remaining wash liquid segment. Air bubbles in the wash
liquid segment, as introduced along pump tubes 52, tend
to break-up the solid phase packed by the magnetic trap
60 and accelerate resuspension of the same in the wash
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. . .
liquid to ensure complete removal of any liquid phase, ;~
i.e. unbound labelled or unlabelled antigens, from the
surfaces thereof. As the second magnetic trap 62 is
energized, the solid phase is again swept from the ~-ash
liquid segment.
In a particularly preferred embodiment of the
in~ention, conduit 56 passing through the wash arrange-
ment 58 is connected to the inlet of a three-port two-
position valve 70, the outputs of such valve being
connected to a solid-phase scintillation counter 72
(position 1) and waste (position II), respectively.
Also, an additional three-port, two position valve 76
is provided, having an inlet connected along conduit 78
to pump tube 80, whose inlet is connected to a source 82
of buffer, and having outlets connected to waste W
(position I) and solid-phase counter 72 (position II).
Valves 70 and 76 are controlled simultaneously by pro-
grammer 64. ~n additional air pump -tube 84, llaving its
inlet exposed to air, is connected to conduit 78, so as
to periodically introduce air bubbles into the buffer
stream flowed along conduit 78. The buffer liquid pumped
along tube 78 is used for cleaning the solid-phase counter
72. As known, the presence of air bubbles alons conduit
78 serves to accelerate the cleaning of any residues of
a preceding sample within the solid-phase counter. When
the solid phase in magnetic trap arrangement 58 has been
thoroushly washed and prior to the appearance of the next
successive sample adjacent the light source 66, at time
t3 of Figure 2, magnetic trap 62 is de-energized and
valves 70 and 72 are operated momentarily to position I,
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to direct th~ solid phass, now suspended in wash liquid,
to solid-phase counter 72 and the segmented buffer stream
along conduit 78 to waste. At this time, the solid phase
is passed through the storage coil 79 of solid-phase
counter 72 and its radioactivity measured. Such measure-
ments can be recorded, for example, by a print-out
recorder 80~ Subsequently, valves 70 and 72 are operated
to position II, to direct the fluid stream along conduit
58 to waste and the segmented buffer stream alon~ conduit
78 through the solid-phase counter, preparatory to the
washing and measurement of the sol.id-phase in a next
sample.
It will be evid~ent that the liquid-phase can be
measured, if desired, rather than the solid phase~ To
this end, a liquid-phase scintillation counter could be
substituted for the solid-phase counter 74. In such
event, the magnetic traps 60 and 62 arc operated, as
described, to sweep out the solid-phase from the aliquots
of the same'~ample. Concurrentl~, valves 70 and 72 are
controlled (to position I) to pass the separated liquid
phase directly to the storage coil of the liquid-phase
counter and while magnetic traps 60 and 62 arc energized.
Subsequently, valves 70 and 72 are operated to position
II, prior to de-energization of magnetic traps 60 and G2,
such that the solid-phase re-suspended in thc wash liquid
is passed to waste and the segmented buffcr liquid is
passed to wash the liquid-phase counter. In either event,
it can be appreciated that the controlled specific gravity
of the magnetic particles, on which the solid phase is
immobilized, and the magnetic in-line trapping technique
described, co-operate to achieve a positive separation of
1~801Z3 ,
the solid and liquid phases, without deteriorating the
wash characteristics of the system.
The individual samples
passed along the conduit 28 may be reacted selectively.
For example, we can provide a plurality of solid phase
sources 20 and label sources 24, each having an assoc-
iated yump tube 30 and return conduit 30', each of wllich
can be connected to a respective three part, two-
position changeover valve. The outputs of tlle change-
over valves for each of the solid phase and label
systems as well as the outputs of the buffer valves
may be connected to corresponding inlets of a multi
input/single output valve, whose output is connected
to junctions A and B.
Each of the single output valves is corltrolled
in response to information read frorn the individual
receptacle 16, so as to introduce the appropriate solid
phase and label phase, in phase with each other, at
junctions B and A, so as to react selectively each sample.
Also, the output on recorder 88 may be appropriately
identified.
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