Note: Descriptions are shown in the official language in which they were submitted.
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MASS SPECTROMETER
The present invention relates to an ion source and
a mass spectrometer comprising an ion source. The
preferred embodiment relates to an Electrospray
Ionisation ("ESI") and an Atmospheric Pressure Chemical
Ionisation ("APCI") ion source preferably used in
conjunction with a mass spectrometer.
The combination of Electrospray ionisation and mass
spectrometry is a powerful technique for the analysis of
organic compounds. Electrospray ionisation involves
passing a solution of analyte in a volatile solvent
through a capillary tube. The capillary tube is
maintained at a relatively high potential with respect
to a chamber surrounding the capillary tube and with
respect to ground. A concentric flow of high velocity
nitrogen is commonly provided at the tip of the
capillary tube to aid the nebulisation process. The
relatively high electric field which is generated
penetrates into the liquid volume at the capillary tip
and results in a partial separation of positive and
negative electrolyte ions. When, for example, a
positive potential is applied to the capillary tube then
negative ions will be driven or attracted towards the
inner capillary wall whilst positive ions will become
enriched at the liquid-gas interface. Droplets with a
net positive charge will then form at and be emitted
from the capillary tip when the combined electrostatic
and electrohydrodynamic forces exceed the liquid surface
tension.
Heat may be applied to the charged droplets which
will result in a further decrease in droplet radius at
constant charge. A point is reached, known as the
Rayleigh limit, wherein the coulombic repulsion of the
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charges exceeds the surface tension. The droplets then
undergo fissions forming even smaller charged droplets
or micro-droplets. The desolvation process continues
until ions are liberated into the gas phase by the
5 process of ion evaporation or charge residue. At least
some of the resulting ions are then admitted into a mass
spectrometer for subsequent mass analysis.
For liquid flow rates in the range 10-1000 nl/min
Electrospray ionisation can usually proceed efficiently
10 without the need to apply heat in the vicinity of the
capillary tip. However, for mobile phase flow rates
which are typically encountered in Liquid Chromatography
Mass Spectrometry ("LC/MS") which may be up to or in
excess of 1 ml/min then it often becomes necessary to
15 apply a significant amount of heat to the droplets
emerging from the capillary tube in order to improve the
ionisation efficiency and overall system sensitivity.
In particular, it is known to surround the capillary
tubes with a further (secondary) flow of nitrogen gas
20 which has been heated. The amount of heat required to
improve the ionisation efficiency increases with the
flow rate and with the proportion of water in the liquid
being ionised.
It is desired to provide an improved ion source.
25 According to a first main aspect of the present
invention there is provided an ion source comprising two
flow devices (e.g. capillary tubes).
According to an aspect of the present invention
there is provided an ion source comprising:
30 a probe comprising a first flow device and a second
flow device; and
a combustion source arranged downstream of the
probe.
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The ion source according to the preferred
embodiment enables a combustible gas or vapour to
perform the dual function of aiding droplet formation at
the tip of the probe whilst also supplying heat to aid
desolvation when combusted by the combustion source.
At least a portion of, or substantially the whole
of, the second flow device preferably surrounds,
envelopes or encloses at least a portion of, or
substantially the whole of, the first flow device. The
first flow device and the second flow device are
preferably co-axial or substantially co-axial.
The first and/or second flow devices preferably
comprise one or more capillary tubes or other form of
tube.
An analyte solution or liquid or flow is preferably
supplied, in use, to the first flow device and/or the
second flow device. The analyte solution or liquid or
flow is preferably supplied, in use, to the first flow
device and/or the second flow device at a flow rate
selected from the group consisting of: (i) < 1 1/min;
(ii) 1-10 1/min; (iii) 10-50 gl/min; (iv) 50-100
1/min; (v) 100-200 1/min; (vi) 200-300 1/min; (vii)
300-400 1/min; (viii) 400-500 1/min; (ix) 500-600
1/min; (x) 600-700 1/min; (xi) 700-800 1/min; (xii)
800-900 1/min; (xiii) 900-1000 1/min; and (xiv) > 1000
1/min.
A first gas or vapour is preferably supplied, in
use, to the first flow device and/or the second flow
device. The first gas or vapour preferably aids
nebulisation of an analyte solution or liquid or flow.
The first gas or vapour is preferably combustible and is
preferably selected from the group consisting of: (i)
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acetone; (ii) acetylene; (iii) benzene; (iv) butane; (v)
butyl alcohol (butanol); (vi) diethyl ether; (vii)
ethane; (viii) ethyl alcohol (ethanol); (ix) ethylene;
(x) ethylene oxide; (xi) hexane; (xii) hydrogen; (xiii)
isopropyl alcohol (isopropanol); (xiv) methane; (xv)
methyl alcohol (methanol); (xvi) methyl ethyl ketone;
(xvii) n-pentane; (xviii) propane; (xix) propylene; (xx)
styrene; (xxi) toluene; (xxii) xylene; (xxiii) carbon
monoxide; (xxiv) a saturated hydrocarbon; (xxv) an
unsaturated hydrocarbon; (xxvi) an alcohol; (xxvii) an
ester; (xxviii) an ether; (xxix) a hydrocarbon; (xxx)
gasoline; (xxxi) jet fuel; (xxxii) naphtha; (xxxiii)
turpentine; (xxxiv) a cyclic compound; (xxxv) a ketone;
(xxxvi) an inorganic gas; (xxxvii) an organic gas;
(xxxviii) hydrogen sulfide; (xxxix) ammonia; (xxxx)
propanol; (xxxxi) ethyl acetate; (xxxxii) heptane; and
(xxxxiii) exlene.
However, according to an alternative less preferred
embodiment the first gas may simply support combustion
and hence may comprise air or oxygen.
The first gas or vapour is preferably supplied, in
use, to the first flow device and/or the second flow
device at a pressure selected from the group consisting
of: (i) < 1 bar; (ii) 1-2 bar; (iii) 2-3 bar; (iv) 3-4
bar; (v) 4-5 bar; (vi) 5-6 bar; (vii) 6-7 bar; (viii) 7-
8 bar; (ix) 8-9 bar; (x) 9-10 bar; and (xi) > 10 bar.
The first gas or vapour preferably enhances or adds
to the combustion of a second gas or vapour which is
preferably combusted by the combustion source. The
first gas or vapour preferably supplies heat when
combusted to aid desolvation of droplets.
The combustion source preferably comprises a blue
flame torch, a gas torch or a blow torch.
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The combustion source is preferably arranged to
combust a second gas or vapour which is preferably
directly supplied to the combustion source. The second
gas or vapour preferably includes one or more gases or
5 vapours selected from the group consisting of: (i)
acetone; (ii) acetylene; (iii) benzene; (iv) butane; (v)
butyl alcohol (butanol); (vi) diethyl ether; (vii)
ethane; (viii) ethyl alcohol (ethanol); (ix) ethylene;
(x) ethylene oxide; (xi) hexane; (xii) hydrogen; (xiii)
10 isopropyl alcohol (isopropanol); (xiv) methane; (xv)
methyl alcohol (methanol); (xvi) methyl ethyl ketone;
(xvii) n-pentane; (xviii) propane; (xix) propylene; (xx)
styrene; (xxi) toluene; (xxii) xylene; (xxiii) carbon
monoxide; (xxiv) a saturated hydrocarbon; (xxv) an
15 unsaturated hydrocarbon; (xxvi) an alcohol; (xxvii) an
ester; (xxviii) an ether; (xxix) a hydrocarbon; (xxx)
gasoline; (xxxi) jet fuel; (xxxii) naphtha; (xxxiii)
turpentine; (xxxiv) a cyclic compound; (xxxv) a ketone;
(xxxvi) an inorganic gas; (xxxvii) an organic gas;
20 (xxxviii) hydrogen sulfide; (xxxix) ammonia; (xxxx)
propanol; (xxxxi) ethyl acetate; (xxxxii) heptane; and
(xxxxiii) exlene.
The probe preferably has a first longitudinal axis
and the combustion source preferably has a second
25 longitudinal axis. The angle between the first
longitudinal axis and the second longitudinal axis is
preferably selected from the group consisting of: (i) 0-
10'; (ii) 10-20'; (iii) 20-30'; (iv) 30-40'; (v) 40-50';
(vi) 50-60'; (vii) 60-70'; (viii) 70-80'; (ix) 80-90';
30 (x) 85-95'; (xi) 90-100'; (xii) 100-110'; (xiii) 1100-
120'; (xiv) 120-130'; (xv) 130-140'; (xvi) 140-150';
(xvii) 150-160'; (xviii) 160-170'; and (xix) 170-180'.
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The ion source preferably further comprises an
enclosure for enclosing the probe and/or the combustion
source. The enclosure preferably comprises a gas inlet
port and a gas outlet port. A background gas is
5 preferably introduced, in use, to the enclosure via the
gas inlet port. The background gas preferably supports
combustion and hence preferably comprises air or oxygen.
The enclosure is preferably maintained, in use, at a
pressure selected from the group consisting of: (i) <
10 100 mbar; (ii) 100-500 mbar; (iii) 500-600 mbar; (iv)
600-700 mbar; (v) 700-800 mbar; (vi) 800-900 mbar; (vii)
900-1000 mbar; (viii) 1000-1100 mbar; (ix) 1100-1200
mbar; (x) 1200-1300 mbar; (xi) 1300-1400 mbar; (xii)
1400-1500 mbar; (xiii) 1500-2000 mbar; and (xiv) > 2000
15 mbar.
According to a preferred embodiment the ion source
comprises an Electrospray ion source. The ion source
preferably comprises a spray device for spraying a
sample and for causing the sample to form droplets. The
20 first flow device and/or the second flow device are
preferably maintained, in use, at a voltage or relative
potential (preferably relative to ground or relative to
the potential of the ion block or inlet aperture of a
mass spectrometer, or less preferably relative to each
25 other) of: (i) < 1 kV; (ii) 1-2 kV; (iii) 2-3 kV;
(iv) 3-4 kV; (v) 4-5 kV; (vi) 5-6 kV; (vii) 6-7
kV; (viii) 7-8 kV; (ix) 8-9 kV; (x) 9-10 kV; and
(xi) > 10 kV.
According to an alternative preferred embodiment
30 the ion source may comprise an Atmospheric Pressure
Chemical Ionisation ion source. A corona discharge
device is preferably arranged downstream of the
combustion source. The corona discharge device
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preferably comprises a corona pin or needle. In a mode
of operation a current is preferably applied to the
corona discharge device selected from the group
consisting of: (i) < 0.1 pA; (ii) 0.1-0.2 pA; (iii) 0.2-
0.3 pA; (iv) 0.3-0.4 pA; (v) 0.4-0.5 pA; (vi) 0.5-0.6
pA; (vii) 0.6-0.7 pA; (viii) 0.7-0.8 pA; (ix) 0.8-0.9
pA; (x) 0.9-1.0 pA; and (xi) > 1 pA.
In a mode of operation a voltage is preferably
applied to the corona discharge device or the corona
discharge device is preferably maintained at a relative
potential (preferably relative to ground or relative to
the potential of the ion block or inlet aperture of a
mass spectrometer) selected from the group consisting
of: (i) < 1 kV; (ii) 1-2 kV; (iii) 2-3 kV; (iv)
3-4 kV; (v) 4-5 kV; (vi) 5-6 kV; (vii) 6-7 kV;
(viii) 7-8 kV; (ix) 8-9 kV; (x) 9-10 kV; and (xi)
> 10 kV.
The first flow device and/or the second flow device
may be maintained, in use, at a voltage or relative
potential (preferably relative to ground or relative to
the potential of the ion block or inlet aperture of a
mass spectrometer, or less preferably relative to each
other) selected from the group consisting of: (i) 0-
100 V; (ii) 100-200 V; (iii) 200-300 V; (iv) 300-
400 V; (v) 400-500 V; (vi) 500-600 V; (vii) 600-
700 V; (viii) 700-800 V; (ix) 800-900 V; (x) 900-
1000 V; and (xi) > 1000 V.
According to less preferred embodiments the ion
source may be selected from the group consisting of: (i)
an Atmospheric Pressure Photo Ionisation ("APPI") ion
source; (ii) a Laser Desorption Ionisation ("LDI") ion
source; (iii) an Inductively Coupled Plasma ("ICP") ion
source; (iv) an Electron Impact ("El") ion source; (v) a
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Chemical Ionisation ("CI") ion source; (vi) a Field
Ionisation ("Fl") ion source; (vii) a Fast Atom
Bombardment ("FAB") ion source; (viii) a Liquid
Secondary Ion Mass Spectrometry ("LSIMS") ion source;
(ix) an Atmospheric Pressure Ionisation ("API") ion
source; (x) a Field Desorption ("FD") ion source; (xi) a
Matrix Assisted Laser Desorption Ionisation ("MALDI")
ion source; (xii) a Desorption/Ionisation on Silicon
("DIOS") ion source; (xiii) a Desorption Electrospray
Ionisation ("DESI") ion source; and (xiv) a Nickel-63
radioactive ion source.
According to a further aspect of the present
invention there is provided a mass spectrometer
comprising an ion source as described above.
The mass spectrometer preferably further comprises
an ion sampling cone or an ion sampling orifice arranged
downstream of the combustion source. The mass
spectrometer may comprise one or more electrodes
arranged opposite or adjacent to the ion sampling cone
or the ion sampling orifice which in use act to deflect,
attract, direct or repel at least some ions towards the
ion sampling cone or the ion sampling orifice of the
mass spectrometer.
According to the preferred embodiment the ion
source is connected, in use, to a liquid chromatograph.
However, according to a less preferred embodiment the
ion source may be connected, in use, to a gas
chromatograph.
The mass spectrometer preferably further comprises
a mass analyser selected from the group consisting of:
(i) an orthogonal acceleration Time of Flight mass
analyser; (ii) an axial acceleration Time of Flight mass
analyser; (iii) a quadrupole mass analyser; (iv) a
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Penning mass analyser; (v) a Fourier Transform Ion
Cyclotron Resonance ("FTICR") mass analyser; (vi) a 2D
or linear quadrupole ion trap; (vii) a Paul or 3D
quadrupole ion trap; and (viii) a magnetic sector mass
analyser.
According to another aspect of the present
invention there is provided an Electrospray Ionisation
ion source comprising:
a probe comprising a first flow device and a second
flow device; and
a combustion source arranged downstream of the
probe.
According to another aspect of the present
invention there is provided an Atmospheric Pressure
Chemical Ionisation ion source comprising:
a probe comprising a first flow device and a second
flow device; and
a combustion source arranged downstream of the
probe.
According to another aspect of the present
invention there is provided an ion source comprising:
a probe comprising a first flow device and a second
flow device; and
an ignition source arranged downstream of the
probe;
wherein, in use, a combustible gas is supplied to
the first flow device and/or the second flow device.
Preferably, the ignition source comprises a spark
gap, a discharge device or an ignition device.
According to another aspect of the present
invention there is provided a method of ionising a
sample comprising:
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providing a probe comprising a first flow device
and a second flow device;
supplying a sample to one of the flow devices;
supplying a first gas or vapour to another of the
flow devices; and
combusting the first gas or vapour using a
combustion source arranged downstream of the probe.
According to another aspect of the present
invention there is provided a method of mass
spectrometry comprising a method of ionising a sample as
described above.
According to a second main aspect of the present
invention there is provided an ion source comprising
three flow devices (e.g. capillary tubes).
According to an aspect of the present invention
there is provided an ion source comprising:
a probe comprising a first flow device, a second
flow device and a third flow device, wherein, in use, a
first gas or vapour is supplied to one of the flow
devices and a further gas or vapour is supplied to
another of the flow devices.
Preferably, a combustion source is arranged
downstream of the probe.
At least a portion of or substantially the whole of
the second flow device preferably surrounds, envelopes
or encloses at least a portion of or substantially the
whole of the first flow device. Similarly, preferably
at least a portion of or substantially the whole of the
third flow device surrounds, envelopes or encloses at
least a portion of or substantially the whole of the
second flow device and/or the first flow device.
According to the preferred embodiment the first
flow device and/or the second flow device and/or the
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third flow device are co-axial or substantially co-
axial.
The first flow device preferably comprises one or
more capillary tubes or tubes, the second flow device
5 likewise preferably comprises one or more capillary
tubes or tubes and the third flow device also preferably
comprises one or more capillary tubes or tubes.
According to the preferred embodiment an analyte
solution or liquid or flow is supplied, in use, to the
10 first flow device and/or the second flow device and/or
the third flow device. The analyte solution or liquid
or flow is preferably supplied, in use, at a flow rate
selected from the group consisting of: (i) < 1 1/min;
(ii) 1-10 1/min; (iii) 10-50 1/min; (iv) 50-100
15 1/min; (v) 100-200 1/min; (vi) 200-300 1/min; (vii)
300-400 1/min; (viii) 400-500 1/min; (ix) 500-600
1/min; (x) 600-700 1/min; (xi) 700-800 1/min; (xii)
800-900 1/min; (xiii) 900-1000 1/min; and (xiv) > 1000
1/min.
20 A first gas or vapour is preferably supplied, in
use, to the first flow device and/or the second flow
device and/or the third flow device. The first gas or
vapour preferably aids nebulisation of an analyte
solution or liquid or flow.
25 The first gas or vapour is preferably combustible
and preferably includes one or more gases or vapours
selected from the group consisting of: (i) acetone; (ii)
acetylene; (iii) benzene; (iv) butane; (v) butyl alcohol
(butanol); (vi) diethyl ether; (vii) ethane; (viii)
30 ethyl alcohol (ethanol); (ix) ethylene; (x) ethylene
oxide; (xi) hexane; (xii) hydrogen; (xiii) isopropyl
alcohol (isopropanol); (xiv) methane; (xv) methyl
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alcohol (methanol); (xvi) methyl ethyl ketone; (xvii) n-
pentane; (xviii) propane; (xix) propylene; (xx) styrene;
(xxi) toluene; (xxii) xylene; (xxiii) carbon monoxide;
(xxiv) a saturated hydrocarbon; (xxv) an unsaturated
hydrocarbon; (xxvi) an alcohol; (xxvii) an ester;
(xxviii) an ether; (xxix) a hydrocarbon; (xxx) gasoline;
(xxxi) jet fuel; (xxxii) naphtha; (xxxiii) turpentine;
(xxxiv) a cyclic compound; (xxxv) a ketone; (xxxvi) an
inorganic gas; (xxxvii) an organic gas; (xxxviii)
hydrogen sulfide; (xxxix) ammonia; (xxxx) propanol;
(xxxxi) ethyl acetate; (xxxxii) heptane; and (xxxxiii)
exlene.
According to an alternative embodiment the first
gas supports combustion and hence preferably comprises
air or oxygen.
Preferably, the first gas or vapour is supplied, in
use, to the first flow device and/or the second flow
device and/or the third flow device at a pressure
selected from the group consisting of: (i) < I bar; (ii)
1-2 bar; (iii) 2-3 bar; (iv) 3-4 bar; (v) 4-5 bar; (vi)
5-6 bar; (vii) 6-7 bar; (viii) 7-8 bar; (ix) 8-9 bar;
(x) 9-10 bar; and (xi) > 10 bar.
The first gas or vapour preferably enhances the
combustion of a second gas or vapour which is combusted
by the combustion source. The first gas or vapour
preferably supplies heat when combusted to aid
desolvation of droplets.
A further gas or vapour is preferably supplied, in
use, to the first flow device and/or the second flow
device and/or the third flow device.
The further gas or vapour may less preferably aid
nebulisation of an analyte solution or liquid or flow.
The further gas or vapour may less preferably be
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combustible and may include one or more gases or vapours
selected from the group consisting of: (i) acetone; (ii)
acetylene; (iii) benzene; (iv) butane; (v) butyl alcohol
(butanol); (vi) diethyl ether; (vii) ethane; (viii)
5 ethyl alcohol (ethanol); (ix) ethylene; (x) ethylene
oxide; (xi) hexane; (xii) hydrogen; (xiii) isopropyl
alcohol (isopropanol); (xiv) methane; (xv) methyl
alcohol (methanol); (xvi) methyl ethyl ketone; (xvii) n-
pentane; (xviii) propane; (xix) propylene; (xx) styrene;
10 (xxi) toluene; (xxii) xylene; (xxiii) carbon monoxide;
(xxiv) a saturated hydrocarbon; (xxv) an unsaturated
hydrocarbon; (xxvi) an alcohol; (xxvii) an ester;
(xxviii) an ether; (xxix) a hydrocarbon; (xxx) gasoline;
(xxxi) jet fuel; (xxxii) naphtha; (xxxiii) turpentine;
15 (xxxiv) a cyclic compound; (xxxv) a ketone; (xxxvi) an
inorganic gas; (xxxvii) an organic gas; (xxxviii)
hydrogen sulfide; (xxxix) ammonia; (xxxx) propanol;
(xxxxi) ethyl acetate; (xxxxii) heptane; and (xxxxiii)
exlene.
20 However, more preferably, the further gas
preferably supports combustion and hence comprises air
or oxygen.
The further gas or vapour is preferably supplied,
in use, to the first flow device and/or the second flow
25 device and/or the third flow device at a pressure
selected from the group consisting of: (i) < 1 bar; (ii)
1-2 bar; (iii) 2-3 bar; (iv) 3-4 bar; (v) 4-5 bar; (vi)
5-6 bar; (vii) 6-7 bar; (viii) 7-8 bar; (ix) 8-9 bar;
(x) 9-10 bar; and (xi) > 10 bar.
30 The further gas or vapour may enhance the
combustion of a second gas or vapour which is combusted,
in use, by the combustion source. The further gas or
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vapour may less preferably supply heat when combusted to
aid desolvation of droplets.
The ion source preferably further comprises a
combustion source selected from the group consisting of:
5 (i) a blue flame torch; (ii) a gas torch; and (iii) a
blow torch. The combustion source is preferably
arranged to directly combust a second gas or vapour.
The combustion source may be directly supplied with
the second gas or vapour. The second gas or vapour is
10 preferably combustible and may include one or more gases
or vapours selected from the group consisting of: (i)
acetone; (ii) acetylene; (iii) benzene; (iv) butane; (v)
butyl alcohol (butanol); (vi) diethyl ether; (vii)
ethane; (viii) ethyl alcohol (ethanol); (ix) ethylene;
15 (x) ethylene oxide; (xi) hexane; (xii) hydrogen; (xiii)
isopropyl alcohol (isopropanol); (xiv) methane; (xv)
methyl alcohol (methanol); (xvi) methyl ethyl ketone;
(xvii) n-pentane; (xviii) propane; (xix) propylene; (xx)
styrene; (xxi) toluene; (xxii) xylene; (xxiii) carbon
20 monoxide; (xxiv) a saturated hydrocarbon; (xxv) an
unsaturated hydrocarbon; (xxvi) an alcohol; (xxvii) an
ester; (xxviii) an ether; (xxix) a hydrocarbon; (xxx)
gasoline; (xxxi) jet fuel; (xxxii) naphtha; (xxxiii)
turpentine; (xxxiv) a cyclic compound; (xxxv) a ketone;
25 (xxxvi) an inorganic gas; (xxxvii) an organic gas;
(xxxviii) hydrogen sulfide; (xxxix) ammonia; (xxxx)
propanol; (xxxxi) ethyl acetate; (xxxxii) heptane; and
(xxxxiii) exlene.
The probe preferably has a first longitudinal axis
30 and the combustion source preferably has a second
longitudinal axis and wherein the angle between the
first longitudinal axis and the second longitudinal axis
is selected from the group consisting of: (i) 0-10';
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(ii) 10-20'; (iii) 20-30 ; (iv) 30-40'; (v) 40-50'; (vi)
50-60'; (vii) 60-70'; (viii) 70-800; (ix) 80-90'; (x)
85-95'; (xi) 90-100'; (xii) 100-110'; (xiii) 110 -120 ;
(xiv) 120-130'; (xv) 130-140'; (xvi) 140-150'; (xvii)
150-160'; (xviii) 160-170 ; and (xix) 170-1800.
The ion source preferably further comprises an
enclosure for enclosing the probe and/or a combustion
source. The enclosure preferably comprises a gas inlet
port and a gas outlet port. A background gas is
preferably introduced, in use, to the enclosure via the
gas inlet port. The background gas preferably supports
combustion and hence the background gas preferably
comprises air or oxygen.
The enclosure is preferably maintained, in use, at
a pressure selected from the group consisting of: (i) <
100 mbar; (ii) 100-500 mbar; (iii) 500-600 mbar; (iv)
600-700 mbar; (v) 700-800 mbar; (vi) 800-900 mbar; (vii)
900-1000 mbar; (viii) 1000-1100 mbar; (ix) 1100-1200
mbar; (x) 1200-1300 mbar; (xi) 1300-1400 mbar; (xii)
1400-1500 mbar; (xiii) 1500-2000 mbar; and (xiv) > 2000
mbar.
According to an embodiment the ion source comprises
an Electrospray ion source. The ion source preferably
comprises a spray device for spraying a sample and for
causing the sample to form droplets. The first flow
device and/or the second flow device and/or the third
flow device are preferably maintained, in use, at a
voltage or relative potential (preferably relative to
ground or relative to the potential of the ion block or
inlet aperture of a mass spectrometer, or less
preferably relative to each other) of: (i) < 1 kV;
(ii) 1-2 kV; (iii) 2-3 kV; (iv) 3-4 kV; (v) 4-5
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kV; (vi) 5-6 kV; (vii) 6-7 kV; (viii) 7-8 kV; (ix)
8-9 kV; (x) 9-10 kV; and (xi) > 10 kV.
According to an alternative embodiment the ion
source may comprise an Atmospheric Pressure Chemical
5 Ionisation ion source. The ion source preferably
comprises a corona discharge device arranged downstream
of the combustion source. The corona discharge device
preferably comprises a corona pin or needle. In a mode
of operation a current is preferably applied to the
10 corona discharge device selected from the group
consisting of: (i) < 0.1 A; (ii) 0.1-0.2 pA; (iii) 0.2-
0.3 pA; (iv) 0.3-0.4 pA; (v) 0.4-0.5 pA; (vi) 0.5-0.6
pA; (vii) 0.6-0.7 pA; (viii) 0.7-0.8 pA; (ix) 0.8-0.9
pA; (x) 0.9-1.0 pA; and (xi) > 1 pA.
15 In a mode of operation a voltage is preferably
applied to the corona discharge device or the corona
discharge device is preferably maintained at a relative
potential (preferably relative to ground or relative to
the potential of the ion block or inlet aperture of a
20 mass spectrometer) selected from the group consisting
of: (i) < 1 kV; (ii) 1-2 kV; (iii) 2-3 kV; (iv)
3-4 kV; (v) 4-5 kV; (vi) 5-6 kV; (vii) 6-7 kV;
(viii) 7-8 kV; (ix) 8-9 kV; (x) 9-10 kV; and (xi)
> 10 kV.
25 The first flow device and/or the second flow device
and/or the third flow device is preferably maintained,
in use, at a voltage or relative potential (preferably
relative to ground or relative to the potential of the
ion block or inlet aperture of a mass spectrometer, or
30 less preferably relative to each other) selected from
the group consisting of: (i) 0-100 V; (ii) 100-200
V; (iii) 200-300 V; (iv) 300-400 V; (v) 400-500 V;
CA 02496013 2005-02-03
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(vi) 500-600 V; (vii) 600-700 V; (viii) 700-800 V;
(ix) 800-900 V; (x) 900-1000 V; and (xi) > 1000 V.
According to less preferred embodiments the ion
source is selected from the group consisting of: (i) an
Atmospheric Pressure Photo Ionisation ("APPI") ion
source; (ii) a Laser Desorption Ionisation ("LDI") ion
source; (iii) an Inductively Coupled Plasma ("ICP") ion
source; (iv) an Electron Impact ("El") ion source; (v) a
Chemical Ionisation ("CI") ion source; (vi) a Field
Ionisation ("Fl") ion source; (vii) a Fast Atom
Bombardment ("FAB") ion source; (viii) a Liquid
Secondary Ion Mass Spectrometry ("LSIMS") ion source;
(ix) an Atmospheric Pressure Ionisation ("API") ion
source; (x) a Field Desorption ("FD") ion source; (xi) a
Matrix Assisted Laser Desorption Ionisation ("MALDI")
ion source; (xii) a Desorption/Ionisation on Silicon
("DIOS") ion source; (xiii) a Desorption Electrospray
Ionisation ("DESI") ion source; and (xiv) a Nickel-63
radioactive ion source.
According to an aspect of the present invention
there is provided a mass spectrometer comprising an ion
source as described above.
The mass spectrometer preferably further comprises
an ion sampling cone or an ion sampling orifice arranged
downstream of a combustion source.
The mass spectrometer preferably further comprises
one or more electrodes arranged opposite or adjacent to
the ion sampling cone or the ion sampling orifice so as
to deflect, attract, direct or repel at least some ions
towards the ion sampling cone or the ion sampling
orifice of the mass spectrometer.
The ion source is preferably connected, in use, to
a liquid chromatograph. However, according to a less
CA 02496013 2005-02-03
.T.
- 18 -
preferred embodiment the ion source may be connected, in
use, to a gas chromatograph.
The mass spectrometer preferably further comprises
a mass analyser selected from the group consisting of:
5 (i) an orthogonal acceleration Time of Flight mass
analyser; (ii) an axial acceleration Time of Flight mass
analyser; (iii) a quadrupole mass analyser; (iv) a
Penning mass analyser; (v) a Fourier Transform Ion
Cyclotron Resonance ("FTICR") mass analyser; (vi) a 2D
10 or linear quadrupole ion trap; (vii) a Paul or 3D
quadrupole ion trap; and (viii) a magnetic sector mass
analyser.
According to an aspect of the present invention
there is provided an Electrospray Ionisation ion source
15 comprising:
a probe comprising a first flow device, a second
flow device and a third flow device, wherein, in use, a
first gas or vapour is supplied to one of the flow
devices and a further gas or vapour is supplied to
20 another of the flow devices.
According to an aspect of the present invention
there is provided an Atmospheric Pressure Chemical
Ionisation ion source comprising:
a probe comprising a first flow device, a second
25 flow device and a third flow device, wherein, in use, a
first gas or vapour is supplied to one of the flow
devices and a further gas or vapour is supplied to
another of the flow devices.
According to an aspect of the present invention
30 there is provided an ion source comprising:
a probe comprising a first flow device, a second
flow device and a third flow device, wherein, in use, a
first gas or vapour is supplied to one of the flow
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4
- 19 -
devices and a further gas or vapour is supplied to
another of the flow devices; and
an ignition source arranged downstream of the
probe.
Preferably, the ignition source is selected from
the group consisting of: (i) a spark gap; (ii) a
discharge device; and (iii) an ignition device.
According to an aspect of the present invention
there is provided a method of ionising a sample
comprising:
providing a probe comprising a first flow device, a
second flow device and a third flow device;
supplying a first gas or vapour to one of the flow
devices; and
supplying a further gas or vapour to another of the
flow devices.
According to an aspect of the present invention
there is provided a method of mass spectrometry
comprising a method of ionising a sample as described
above.
Various embodiments of the present invention
together with other arrangements given for illustrative
purposes only will now be described, by way of example
only, and with reference to the accompanying drawings in
which:
Fig. 1 shows a conventional Electrospray ion
source;
Fig. 2 shows the temperature profile for a
conventional Electrospray ion source and for an ion
source according to the preferred embodiment as a
function of axial distance from the probe tip;
Fig. 3 shows a preferred Electrospray ion source
comprising two capillary tubes;
_
_______________________________________________________________________________
________
CA 02496013 2005-02-03
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Fig. 4A shows a mass spectrum obtained using a
conventional ion source, Fig. 4B shows a mass spectrum
obtained using a preferred Electrospray ion source which
includes a combustion source and Fig. 4C shows a control
5 mass spectrum obtained using an ion source as shown in
Fig. 3 but wherein a non-combustible nebulisation gas
was used;
Fig. 5 shows an Electrospray ion source according
to an alternative embodiment comprising three capillary
10 tubes; and
Fig. 6 shows an Atmospheric Pressure Chemical
Ionisation ion source according to a further embodiment.
A known Electrospray ionisation ion source is shown
in Fig. 1. The known arrangement comprises an
15 electrospray probe 1 which comprises an inner capillary
tube 2 and an outer capillary tube 3. A primary gas
flow A of unheated nitrogen is introduced, in use, into
the outer capillary tube 3 in order to aid the
electrospray nebulisation process. The capillary tubes
20 2,3 are surrounded by a hollow conical heating vessel 4
having an annulus outlet. The heating vessel 4 has a
single gas inlet and a secondary nitrogen gas flow B is
arranged to enter the heating vessel 4. The nitrogen
gas within the heating vessel 4 is heated as it passes
25 over an internal resistive heater such that the nitrogen
gas in the secondary nitrogen gas flow B emerges at an
elevated temperature from the annulus outlet.
The primary gas flow A of unheated nitrogen acts as
a fast jet of gas which breaks up the droplets of liquid
30 emerging from the inner capillary 2 into an aerosol i.e.
the purpose of the primary gas flow A is to aid
nebulisation. The secondary gas flow B is directed
towards the exit of the electrospray probe 1 and has the
CA 02496013 2005-02-03
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main purpose of raising the ambient temperature in the
region between the electrospray probe 1 and an ion
sampling cone 5 arranged downstream of the electrospray
probe 1. The main purpose of the heated secondary gas
5 flow B therefore is to aid droplet desolvation and
subsequent ion formation.
In order for a very fine spray or mist of micro-
droplets to be formed, the liquid droplets should
ideally be made as small as possible so that the charged
10 droplets break apart due to the Coulombic repulsion
exceeding the surface tension of the droplet.
Fig. 2 shows the typical temperature profile along
the axis from the tip of an electrospray probe 1 of a
conventional ion source as shown in Fig. 1. The
15 temperature profile due to a preferred ion source as
will be discussed in more detail in relation to Fig. 3
is also shown in Fig. 2. The distance X as shown in
Fig. 2 is the displacement measured from the end of the
electrospray probe 1 as indicated in Fig. 1. The
20 temperature data for the conventional ion source was
obtained by operating a conventional electrospray probe
with no liquid flow, a primary nitrogen nebuliser flow
rate A of 100 1/hr supplied to outer capillary 3, and a
secondary nitrogen desolvation flow rate B of 500 1/hr.
25 The secondary nitrogen flow B was supplied via heating
vessel 4 which was arranged to have a heater temperature
of 500 C and therefore substantially heated the
secondary nitrogen flow B.
It is apparent from Fig. 2 that there is a
30 relatively rapid fall-off in temperature with
displacement or distance from the probe tip 1 (or more
accurately from the heat source 4). As will be
understood by those skilled in the art, it is not
CA 02496013 2005-02-03
= = 4
- 22 -
practically possible to mount the heating vessel 4 any
closer to the electrospray probe 1 due to a number of
mechanical and high voltage design restrictions.
When relatively high liquid flow rates are used
with a conventional electrospray probe 1 such as the
electrospray ion source shown in Fig. 1 and especially
when the sample being ionised has a relatively high
water content, then disadvantageously desolvated ions
are believed to exist only substantially around the
perimeter of the spray emitted from the electrospray
probe 1. The centre of the spray is believed to remain
substantially undesolvated in such circumstances. It is
believed that the heating and desolvation process is
relatively efficient around the perimeter of the emitted
spray but is significantly less efficient towards the
centre of the spray.
A schematic of an ion source according to the
preferred embodiment is shown in Fig. 3 and will now be
discussed. The preferred embodiment comprises a
combustion assisted Electrospray Ionisation ("ESI")
interface or ion source which is preferably coupled, in
use, to a mass spectrometer. The preferred interface or
ion source preferably comprises an electrospray probe 1
which preferably comprises an inner stainless steel
capillary tube 2 and an outer stainless steel capillary
tube 3. According to other less preferred embodiments
the inner capillary tube 2 and/or the outer capillary
tube 3 may be made from other materials. The inner
capillary 2 is preferably approximately 200 mm long and
preferably has an internal diameter of 130 pm and
preferably an external diameter of 230 pm. The outer
capillary 3 is preferably approximately 30 mm long and
CA 02496013 2005-02-03
- 23 -
preferably has an internal diameter of 330 pm and
preferably an external diameter of 630 pm.
A blue-flame gas torch 6 is preferably arranged or
otherwise provided downstream of the exit of the
5 electrospray probe 1. An ion sampling cone 5 or other
entrance to the main body of a mass spectrometer is
preferably arranged downstream of the blue-flame gas
torch 6.
The electrospray probe 1, blue-flame gas torch 6
10 and ion sampling cone 5 which preferably includes an ion
sampling orifice 11 are preferably enclosed or at least
partially enclosed within an enclosure 8. The enclosure
8 preferably includes a gas inlet port 9 and a gas
outlet port 10. The gas outlet port 10 preferably
15 facilitates the venting of undesirable gases to an
appropriate extractor system.
The bore of the inner capillary tube 2 of the probe
1 preferably serves as a conduit for an analyte solution
whilst the bore of the outer capillary tube 3 preferably
20 serves as a conduit for nebuliser/combustion gas or
vapour.
An important feature of the preferred embodiment is
the provision of a more direct method of heating the
droplets emitted or emerging from the electrospray probe
25 1. The preferred ion source exhibits a significantly
enhanced or otherwise improved desolvation process. This
is achieved by providing a gas combustion source between
the exit of the electrospray probe tip 1 and the ion
sampling cone 5.
30 According to the preferred embodiment a nebulising
and combustible gas such as methane may be provided or
supplied to the outer capillary 3 in order to serve the
dual purpose of both aiding droplet formation at the tip
CA 02496013 2005-02-03
- 24 -
of the probe 1 and also of supplying heat via combustion
with the surrounding oxygen-containing atmosphere when
combusted by the blue flame torch 6. The reaction of
methane with oxygen is exothermic by 802 kJ/mole, and
5 the complete combustion of 100 1/hr of methane will
result in approximately 1 kW of available power in order
to enhance desolvation of the droplets emitted from the
electrospray probe 1. This is to be compared with only
approximately 200 W of power in a conventional system
10 assuming in both cases a flow rate of 1 ml/min of 1:1
acetonitrile:water. Although complete combustion of the
combustion gas is not necessarily to be expected due to
limited oxygen penetration, nonetheless the heat is
limited to the very small probe jet volume which results
15 in a high power density and significantly improved
desolvation.
Referring back to Fig. 2, the temperature profile
along the axis of an electrospray probe when using a
preferred ion source (as shown in Fig. 3) is also shown.
20 The temperature profile relating to the preferred ion
source was obtained when 40 1/hr of methane was supplied
to the outer capillary tube 3 of an ion source such as
the one shown in Fig. 3. The methane gas acted both as
a nebulising and combustion gas in atmospheric air.
25 As will be appreciated from Fig. 3, the combustion
of e.g. methane gas supplied to outer capillary 3 may be
initiated and sustained by, for example, a blue flame
butane gas torch 6 which preferably intersects the
methane jet close to the probe tip. The relative
30 temperature profiles shown in Fig. 2 demonstrate the
effectiveness of the heating method according to the
preferred embodiment and show that gas temperatures in
excess of 300 C can be achieved in the vicinity of the
CA 02496013 2005-02-03
- 25 -
ion sampling cone 5 i.e. at a position 10-15 mm
downstream from the probe tip. The ion sampling cone 5
which forms the entrance of the mass spectrometer 12 is
preferably made from stainless steel and preferably
5 comprises an orifice 11 which at its apex is preferably
0.3-0.5 mm in diameter. At least some of the ions
emitted from the electrospray probe 1 preferably pass
through the orifice 11 of the ion sampling cone 5 into a
first low pressure stage of the mass spectrometer 12.
10 The axes of the electrospray probe 1 and the ion
sampling cone 5 preferably lie approximately or
substantially in the same geometrical plane and/or
preferably intersect at an angle of generally or
substantially 90 . However, according to other less
15 preferred embodiments the axes of the electrospray probe
1 and the ion sampling cone 5 may lie in different
planes and/or intersect at angles less than or
substantially greater than 90 .
The orientation of the blue flame gas torch 6 is
20 preferably such that its axis lies generally or
substantially in the same geometrical plane as the axis
of the electrospray probe 1 and/or the axis of the
sampling cone 5. The axis of the blue flame gas torch 6
also preferably generally or substantially intersects
25 the axis of the electrospray probe 1 at a point
substantially or generally downstream of the probe tip
and preferably upstream of the ion sampling cone orifice
11 and ion sampling cone 5. An orthogonal orientation
between the axes of the electrospray probe 1 and the gas
30 torch 6 is preferable but not essential. According to
other less preferred embodiments the gas torch 6 may,
for example, be rotated around a pivot point formed at
the intersection of the axis of the electrospray probe 1
CA 02496013 2005-02-03
- 26 -
and the axis of the gas torch 6. At least a portion of
the blue flame section 13 of the gas torch 6 preferably
intersects the preferably diverging gas jet that
preferably emanates from the electrospray probe tip.
5 Various geometrical parameters may be varied
depending upon experimental conditions such as liquid
flow rate and gas flow rate. For example, as shown in
Fig. 3 the distance Y1 from the tip of the body of the
blue flame gas torch 6 to the axis of the electrospray
10 probe 1 is preferably 10-50 mm, further preferably 25
mm. The distance Y2 from the axis of the electrospray
probe 1 to the inlet of the ion sampling cone 5 or ion
sampling cone orifice 11 is preferably 0-10 mm, further
preferably 3 mm. The distance X1 from the exit of the
15 electrospray probe 1 to the axis of the blue-flame torch
6 is preferably 0-30 mm, further preferably 4 mm., The
distance X2 from the exit of the electrospray probe 1 to
the axis of the ion sampling cone 5 is preferably 5-30
mm, further preferably 12 mm.
20 In operation, a solution containing analyte is
preferably pumped through the inner capillary 2 via or
by means of a solvent delivery system 14 at a flow rate
preferably in the range 1-1000 pl/min. For positive ion
analysis, a voltage of +3 kV is preferably applied to
25 the inner capillary 2 via a high voltage power supply 15
i.e. the inner capillary is preferably maintained a
potential of +3 kV relative to ground or relative to the
potential of the ion block or inlet aperture of a mass
spectrometer. A combustible gas, such as methane, is
30 preferably pumped through the outer capillary 3 via a
pressurized gas cylinder 16 and pressure regulator 17.
The gas flow rate is determined by the regulator
pressure which is preferably set at between 3-7 bar. If
CA 02496013 2005-02-03
- 27 -
the gas supplied to the outer capillary 3 is a pure
combustible gas then oxygen may additionally be supplied
to the system via gas inlet port 9 of the enclosure 8.
The oxygen supplied via gas inlet port 9 may be supplied
either at ambient atmospheric air pressure as air, as
forced air or as a pressurised gas containing oxygen.
The enclosure volume 8 preferably remains substantially
at or generally close to atmospheric pressure.
According to other embodiments gases other than
pure gases may be used as the nebulisation and
combustion gas which is preferably supplied to the outer
capillary 3 via pressure regulator 17. For example,
mixtures comprising a combustible gas in addition with a
combustion supporting gas (i.e. oxygen) may be used.
Preferred combustible gases include methane, hydrogen,
carbon monoxide, saturated hydrocarbons such as butane,
and unsaturated hydrocarbons such as ethylene and
acetylene. However, other less preferred gases or
vapours may be used.
Electrosprayed droplets emerging from the probe tip
preferably move nominally or substantially along the
probe axis in a direction generally towards the ion
sampling cone 5. The droplets then gain preferably
significant heat as they approach the region where the
axis of the blue flame gas torch 6 intersects the axis
of electrospray probe 1. The heat supplied to the
droplets encourages further desolvation. Further
downstream desolvation continues as a result of further
combustion in regions of the gas jet where oxygen
penetration is sufficient. At least some of the gas
phase ions or microdroplets which emerge downstream of
the blue flame torch 6 then preferably enter an ion
sampling cone 5 of a mass spectrometer via an ion
CA 02496013 2005-02-03
- 28 -
sampling cone orifice 11. The ions are then
subsequently mass analysed by the mass spectrometer 12.
The method of combustion assisted electrospray
ionisation according to a preferred embodiment of the
present invention has been demonstrated using a number
of different organic analytes including Reserpine,
Gramicidin-S, Raffinose and Verapamil. Electrospray
ionisation of these analytes using a conventional
Electrospray Ionisation ion source indicated that
Reserpine exhibited the strongest dependency on droplet
heating i.e. the greater the desolvation temperature,
the greater the resulting ion intensity. Consistent
with this, Reserpine was also found to benefit the most
from the strong heating and enhanced desolvation
associated with the combustion assisted Electrospray
Ionisation ion source according to the preferred
embodiment.
Figs. 4A, 48 and 40 show a comparison between the
optimised mass spectral ion intensities observed using a
conventional Electrospray Ionisation ion source and a
combustion assisted Electrospray Ionisation ion source
according to the preferred embodiment as shown in Fig.
3. Data was obtained by infusing a solution of 330
pg/pl of Reserpine in 1:1 acetonitrile:water at a flow
rate of 30 pl/min. A mass spectrum across the range
606.5-611.5 was recorded so as to be approximately
centred on the molecular ion (M1-i+) having a mass to
charge ratio of 609.3 Da. All mass spectra were
obtained by operating the mass spectrometer 12 in a MS
mode of operation. The mass spectrometer 12 comprised a
triple quadrupole mass spectrometer but the mass
spectrometer is preferably not limited to such a design.
CA 02496013 2005-02-03
- 29 -
The intensity scale (detector gain) was the same for all
three mass spectra shown in Figs. 4A-4C.
Fig. 4A shows the optimised ion signal obtained
using a conventional Electrospray Ionisation ion source
5 such as shown in Fig. 1 wherein a primary flow A of
unheated nitrogen at a flow rate of 100 1/hr was
supplied to the outer capillary 3 of the probe 1 in
order to nebulise the liquid emerging from the inner
capillary tube 2. A heating vessel 4 maintained at a
10 temperature of 500 C was used to heat a secondary flow B
of nitrogen gas. The secondary flow B of nitrogen gas
had a flow rate of 800 1/hr and was primarily provided
to aid desolvation.
Fig. 4B shows the optimised ion signal obtained
15 with a combustion assisted Electrospray Ionisation ion
source according to the preferred embodiment using pure
methane as the nebulisation and combustible gas which
was supplied to the outer capillary 3 of the ion source
shown in Fig. 3. The pure methane was supplied at a
20 flow rate of 40 1/hr. An ambient air inlet 9 and a blue
flame butane torch 6 were employed. Although the ion
signal shown in Fig. 4B is saturated, a comparison of
the 13C isotopes for the data shown in Fig. 4A and the
data shown in Fig. 4B indicates that the combustion
25 assisted Electrospray ionisation ion source according to
the preferred embodiment resulted in at least a 4-fold
improvement in the intensity of the Reserpine ion
signal. It is apparent therefore that the preferred ion
source represents a significant improvement compared to
30 conventional ion sources.
Fig. 4C shows by way of a control example the ion
signal obtained using a combustion assisted Electrospray
Ionisation ion source as shown in Fig. 3 but wherein a
CA 02496013 2005-02-03
. . . .
. ,
- 30 -
non-combustible nitrogen gas was used as the
nebulisation gas supplied to the outer capillary 3. The
ion signal shown in Fig. 4C exhibits an approximately
100-fold decrease in ion signal compared to using
methane gas as the nebulisation and combustion gas
according to the preferred embodiment.
Results with Raffinose (data not shown) indicate
that combustion assisted Electrospray ionisation
according to the preferred embodiment using pure methane
as the nebulising and combustion gas is equally
effective in negative ion mode. Accordingly, the
significant increase in ion intensity experienced when
using an ion source according to the preferred
embodiment is not simply due to positive ion gas phase
chemical ionisation of the analyte with methane reagent
ions, but rather is due to the enhanced nebulisation and
heating of the droplets emerging from the electrospray
probe 1 according to the preferred embodiment. It is
also significant to note that no thermal degradation was
observed for the various test analytes.
A further advantage of an Electrospray Ionisation
ion source according to the preferred embodiment is that
a substantially lower overall gas flow rate can be used
with a combustion assisted Electrospray Ionisation ion
source according to the preferred embodiment compared to
a conventional Electrospray Ionisation ion source. In
the examples described above in relation to Figs. 4A and
4B, the total gas flow for the combustion assisted
Electrospray Ionisation ion source according to the
preferred embodiment was only 40 1/hr whereas the total
gas flow rate for the conventional Electrospray
Ionisation ion source was 900 1/hr. Accordingly, the
preferred ion source not only significantly enables a
CA 02496013 2005-02-03
õ
- 31 -
four-fold increase in the ion intensity to be achieved
but also importantly enables the overall gas flow rate
to be significantly reduced by approximately 20-fold.
The preferred embodiment therefore also enables a
significant reduction in operating costs to be achieved.
An ion source according to the preferred embodiment
therefore represents a significant advance in the art.
A modification of the double capillary embodiment
shown and described in relation to Fig. 3 will now be
discussed with reference to Fig. 5. Fig. 5 shows a
triaxial capillary system comprising an inner capillary
2, an intermediate capillary 3 and an outer capillary
3'. The inner capillary 2 and/or the intermediate
capillary 3 and/or the outer capillary 3' are preferably
concentric or substantially co-axial. The inner
capillary 2 preferably carries or is supplied with an
analyte solution. According to an embodiment the
intermediate capillary 3 preferably carries or is
supplied with a combustible gas or gas mixture, whilst
the outer capillary 3' preferably carries or is supplied
with a flow of air, oxygen, or a mixture comprising
oxygen. However, according to an alternative
embodiment, the intermediate capillary 3 may carry or be
supplied with a flow of air, oxygen, or a mixture
comprising oxygen whilst the outer capillary 3' may
carry or be supplied with a combustible gas or gas
mixture.
A further embodiment is shown in Fig. 6 which
relates to an Atmospheric Pressure Chemical Ionisation
("APCI") ion source. According to this embodiment a
corona discharge device 19 is provided downstream of the
blue flame torch 6. The inner capillary 2 of the probe
1 is preferably grounded or held a relative potential of
CA 02496013 2005-02-03
. .
- 32 -
OV relative to the ion block or inlet aperture of the
mass spectrometer 12 (or less preferably is maintained
at a relatively low potential relative to ground) in
contrast to the Electrospray Ionisation ion source shown
and described above in relation to Figs. 3 and 5 wherein
the inner capillary 2 was preferably maintained at a
potential of +3 kV relative to ground or the potential
of the ion block or inlet aperture of the mass
spectrometer 12. According to this embodiment the
combination of a combustible probe gas supplied to outer
capillary 3 and a blue flame torch 6 is utilized. The
combustible gas, such as for example methane, is
preferably supplied to outer capillary 3 and is
preferably used to pneumatically nebulise an analyte
solution which is preferably supplied to inner capillary
2. The inner capillary 2 is preferably grounded.
Desolvation of the resulting droplets emerging from the
probe 1 is then preferably enhanced by the blue flame
torch 6 in substantially the same manner as described
above in relation to the embodiments described in
relation to Figs. 3 and 5. However, ionisation is
primarily initiated by the use of a corona discharge
device 19 which is preferably arranged downstream of the
blue flame torch 6 (although less preferably might be
arranged upstream of the combustion source 6). The
corona discharge device 19 is preferably located
substantially or generally adjacent or opposite to the
ion sampling cone 5 and the ion sampling cone orifice 11
although according to other embodiments the corona
discharge device 19 may be positioned upstream or
slightly downstream of the inlet 11 to the mass
spectrometer 12. A corona discharge is preferably
produced by applying a relatively high voltage e.g. +3-5
CA 02496013 2012-07-06
- 33 -
kV relative to ground (or relative to the potential of
the ion block or inlet aperture of the mass spectrometer
12) to the corona discharge device 19 which preferably
comprises a corona needle. The corona needle 19 is
preferably supported by an insulating flange 20 and is
preferably supplied with a high voltage by a high
voltage source 15.
A further unillustrated embodiment is contemplated
wherein the Atmospheric Pressure Chemical Ionisation ion
source comprises three capillaries 2,3,3' in a similar
manner to the embodiment shown and described in relation
to Fig. 5 in place of the double capillary system 2,3 as
shown in Fig. 6. According to this further embodiment
analyte solution would as before preferably be provided
to the inner capillary tube 2. A nebulisation and
combustion gas is preferably supplied to the
intermediate capillary 3 and a combustion supporting gas
(i.e. oxygen) is preferably supplied to the outer
capillary 3'. Alternatively, the nebulisation and
combustion gas may be supplied to the outer capillary 3'
and the combustion supporting gas (i.e. oxygen) may be
supplied to the intermediate capillary 3.
