US3601609A

US3601609A - Ionization detection device using a nickel-63 radioactive source

Info

Publication number: US3601609A
Application number: US863672A
Authority: US
Inventors: William L Yauger Jr
Original assignee: Tracor Inc
Current assignee: Bankers Trust Co; Tracor Instruments Austin Inc
Priority date: 1965-10-18
Filing date: 1969-09-19
Publication date: 1971-08-24
Anticipated expiration: 1988-08-24
Also published as: FR1496910A

Abstract

Improved ionization detectors capable of analyses at temperatures of 500* C. or more for use with analysis instruments such as gas chromatographs, utilize a radioactive source of nickel-63.

Description

United States Patent [72] Inventor William L. Yauger, Jr. 2,990,492 6/1961 Wellinger et a1 313/54 Baton Rouge. La. 3,176,135 3/1965 Lovelock 250/836 121] App]. No. 863,672 3,361,908 1/1968 Petitjean et a]. 250/836 X [22] Filed Sept. 19,1969 3,104,320 9/1963 Speakman et a1. 250/836 [45] Patented Aug. 24, I971 3,361,908 1/1968 Pettitjean et a1 250/836 [73] Assignec Tracor, Inc. OTHER REFERENCES Ausfimn Shah' t 1'A 1 Ch v 1 35 N 4 A 1963- Continuation of application Ser. No. 467 e a 0 1965 now abandoned' Shoemake et 21].; Radiation Sources for Ionization Detectors in Gas Chromatography" J. 0fG.C.-Aug. 1965; pp. 285- 286.

Kahnet al.; The Emanation of Tritium Gas from Two 4 [ONIZATION DETECTION DEVICE USING A Electron Capture Detectors" J. ofG.C.-Aug. 1965; ppv 287- NICKEL-63 RADIOACTIVE sooner: 12 Claims! 7 Drawing Figs Primary ExaminerArchie R. Borchelt 52 us. on 250 44, y- Roylance, Krugerafld Durkee 250/435 MR 250/836 FT, 313/54 [511 lnLCl ..G0ln23/l2 [50] Field olSearch 250/435 R, 83.6 FT, 44; 313/54 ABSTRACT: Improved ionization detectors capable of [56] References (Med analyses at temperatures of 500C. 01' more for use with anal- UNITED STATES PATENTS ysis instruments such as gas chromatographs, utilize a radioac 2,968,730 l/1961 Morris et al. 313/54 X tive source ofnickel-63.

PATENTED AUB24 I971 SHEET 2 BF 3 oNi 2O 3O 4O 50 -SOURCE ACTIVITY (MILLICURIES) PATENTEB M82419?! SHEET 3 OF 3 3,601,609

CHROMATOGRAM OF ORGANO HALIDES USING Ni ELECTRON CAPTURE DETECTOR 32 mexonmmoiufimwz Bz 55 2 .5512- mmzommwm MINUTES FIG.

IONIZATION DETECTION DEVICE USING A NICKEL-63 EADIOACTIVE SOIUIICE This application is a continuation of Ser. No. 497,099, filed Oct. 18, 1965, now abandoned,

This invention relates to ionization detection in which ionization of gaseous matter within a cell or detector is promoted by emission from a radioactive source. More particularly, this invention pertains to improvements in ionization detectors normally operated at low potentials and functioning, for example, as electron capture detectors (also known as electron affinity detectors), ionization cross section detectors, argon ionization detectors (also referred to as metastable atom detectors), or electron mobility detectors.

ln recent years, ionization detection of the type in question has achieved considerable importance in the field of scientific measurements. For example, electron capture detectors have been found to be extremely sensitive and therefore especially useful in gas chromatography, especially in connection with pesticide trace analysis. Further details relative to this and other fields of application for the foregoing ionization detectors are fully documented in the literature, exemplary references being Lovelock, Anal. Chem. 35, 474( 1963); Lovelock et al., J. Am. Chem. Soc. 82, 43 l 1960); Loveloclt, Anal. Chem. 33, 162(1961); Goodwin et al., Analyst 86, 697(1961); Watts et al., Journal ofthe AOAC 45, 102( 1962); Lovelock, Nature 189, 729(1961); Lovclock et al., Anal. Chem. 33, 1958(1961); Lovelock et al., Nature 193, 540(1962); Landowne et al., Anal. Chem. 34, 726(1962); Reynolds, Chem. and Ind. 1962, p. 729; Lovelock, J. Chromatog. l, (1958); Lovelock et al., Anal. Chem. 35, 460(1963); and references cited in these papers.

Generally speaking, these ionization detectors have been constructed along well-established lines and involve use of the so-called Lovelock geometry (plane parallel electrodes) as do picted, for example, on page 477 of the Lovelock paper first above-cited, or cylindrical geometry (see Shahin et al., Anal. Chem. 35 No.4, Apr. 1963 or pin cup geometry (sec Cook et al., Anal. Chem. 36, No. 12, Nov. 1964 In all cases the detector cell contains a particular radioactive source as the internal B-emitter. Attempts have been made to use a radium isotope (Ra for this purpose but its high noise level and its high gamma emission level and consequent shielding problems have rendered these attempts largely futile. Accordingly, it. has been standard practice in the art to employ tritium occluded in a suitable carrier-usually titanium plated on a stain less steel foil-as the internal source of electrons in most com mercial detectors.

The use of occluded tritium has, however, imposed severe limitations upon the use of these ionization detectors. The chief limitation arises by virtue of the fact that the tritium is readily released to the atmosphere if the fi-emitter is subjected to common operating temperatures, e.g., 200 C. (see liahn et al., J. of G.C., Aug. 1965 pp. 287-288). Accordingly, tritium detectors must be operated at relatively low temperatures in order to avoid the obvious dire consequences of radiation ex posure. in fact, licenses from the United States Atomic Energy Commission permitting use of tritium detectors require installation of upper temperature limit safety devices prohibiting operation of the detectors at temperatures in excess of 225 C. Consequently, commercial detectors are usually factory adjusted so that their heater cartridges will cut off at a safe tcm peraturc, e.g., 200 C.-225 C. Oftentimes it is desired to operate the cells at higher temperatures, temperatures above the safe operating temperatures for tritium sources. ln gas chromatography, for example, the detector must operate at a temperature which is approximately equal to, and preferably above, the terminal temperature of the chromatographic column so that the column effluent will not excessively condense within and on the critical interior parts of the cell. Hence, the temperature limitations imposed on tritium detectors seriously limit the use of the entire chromatographic system in the analysis of high-boiling organic compounds.

Accordingly, an object of this invention is to provide a relia ble ionization detector of the type described in which no hazard to operating personnel is presented even when operating at temperatures as high as 300 C.

Another object is to provide a stable B-emitter of adequate half-life for ionization detectors (electron capture detectors cross section detectors, and the like) in a form which will permit expeditious cleaning particularly in the event of eventual contamination of the detector by substrate oils vaporizing from a chromatographic column.

A further object is to provide ionization detectors which are durable and relatively simple to construct, operate and clean.

Still another object is to provide a B-emitter which is rela tively free of electrical noise in operation and can be readily used in ionization detectors employing any of a variety of cell geometries and modes of operation, e.g., for measuring electron capture, cross section behavior, and the like.

A still further object is to provide a. B-emitter of high off ciency to produce maximum ion current for the least amount of radioactive material present.

Yet another object is to provide an ionization detector em bodying in its construction an electrical insulation material contributing, by virtue of its properties to the durability and usefulness of the entire unit.

These and other objects, features, embodiments, and advantages of this invention will be apparent from the ensuing description, appended claims and accompanying drawings.

ln accordance with this invention the nickel isotope Ni is employed as the ,B-emitter in the ionization detector. More particularly, the detector cells of this invention are composed, in essence, of electrodes in spaced-apart ionization detection relationship, means for confining a flow of gas about the electrodes, and a Ni ,B-source positioned so that it will emit ,8- particles into the gas when the gas is in ionization detection proximity to the electrodes.

A major advantage of Ni as a B-soulrce vis-a-vis tritium occluded in a metal substrate is that Ni is a metal which can be readily formed into a thin film by various techniques, such as electroplating and the like, thereby providing a highly efficient surface emitter. On the other hand, tritium is a gas which can be maintained in the detector cell only by occluding it below or within the surface of a solid metal foil or other solid carrier. This gives rise to reabsorption of ,B-particles within the body of the carrier and for this reason tritiated sources are not highly efficient and do not give uniform emission. Moreover, Ni has been found to be superior to other radioactive metal Bemitters such as Pm, Sr, and Tc, and B-emitters such as Ra and Am Still other radioactive metals have failed entirely as B-emitters for use in ionization detectors.

Another major advantage of the Ni detectors of this invention is that they can be operated at temperatures as high as 500 C. without encountering undue radiation hazards and as a result of scientific investigations conducted to date, the United States Atomic Energy Commission has sanctioned the operation of a particular type of Ni detector cell of this invention at temperatures as high as 300 C. This invention has thus obviated the temperature limitation imposed on tritium detectors and thereby expanded the applicability of ionization detection in chromatographic analysis.

In the Drawings:

FIG. I is a schematic view in longitudinal cross section of an ionization detector embodying the plane parallel electrode (Lovelock) geometry and in which a discrete Ni radioactive source is positioned within the cell;

P10. 2 is another schematic longitudinal cross-sectional view of an ionization detector involving the Lovelock geometry, in this instance a Ni electron source being laminated or plated upon the interior surface of one of the electrodes;

FIG. 3 represents a schematic longitudinal cross-sectional view of an ionization detector embodying cylindrical geometry;

FIG. 4 depicts in schematic longitudinal cross section an ionization detector having pin cup geometry;

FIG. 5 depictsin longitudinal cross section a preferred detector of this invention involving, inter alia, features of cylindrical and pin cup geometries;

FIG. 6 is a graphic presentation of comparative data demonstrating the marked superiority of a Ni B-emitter over an occluded tritium source; and

FIG. 7 is a chromatogram of a complex mixture of organo halide pesticides obtained in a gas chromatograph equipped with a preferred ionization detector of this invention.

Referring to FIGS. 1 and 2, the gas-confining chambers depicted therein are composed of

planar electrodes

10 and 12, cell wall 14, gas inlet tube 16 and gas outlet tube 18. In transverse cross section the overall chamber may have any suitable configuratione.g., it may be square, rectangular, cylindrical, elliptical, polygonal, or the like. Positioned across the inner end of inlet tube 16 is a screen or frit member 20 (e.g., 100- mesh screen having a thickness of 0.010 inch) to assist in distributing the incoming gaseous material substantially uniformly across the cell. Ordinarily, the overall chamber will be encased within a housing (not shown) fitted with heating means (not shown), such as a I00 watt cartridge heater so that the ionization chamber may be maintained at a selected elevated operating temperature. I

In FIG. 1, the Ni B-emitter is in the form ofa foil or disc 22 which is positioned as a discrete member in proximity to the inner face of electrode 10. Although the entire foil or disc 22 may be composed of Ni, it is preferable to use a laminated foil wherein a metal backing foil (e.g., 0.0l0 to 0.020 inch thick gold, nickel, platinum, stainless steel, or the like) is plated with a thin layer (e.g., 0.000l to 0.0l0 inch) of Ni. Besides keeping the amount of Ni to a minimum and thereby reducing the cost of the detector cell unit, the use of a thin plate of Ni on a backing foil provides a most efficicnt ,8- source wherein emission emanates from virtually the entire thin plate of Ni and reabsorption of B-particles within the plate is kept to a minimum. In FIG. 2, the Ni B-emitter is in the fonn of a layer 24 plated directly upon the interior face of electrode 10 and, for the reasons just presented, it is preferable to use a thin plate of Ni. In FIGS. 1 and 2, the Ni faces the gap between the electrodes and is thereby positioned so as to emit B-particles into the gaseous material (e.g., effluent gases from a chromatographic column) as it passes across the electrode gap on its way through the cell.

Ordinarily electrode l0-the one with which. the B-emitter is more closely associated-is the cathode, electrode 12 serving as the anode, with either a DC or a pulsating DC potential applied between the two electrodes. When the detectors of FIGS. 1 and 2 are designed for use in electron capture the spacing between the electrodes 10 and I2 is generally in the order of about 1 cm., and the polarizing voltage is between zero and about 50 volts (DC or pulse). For use in measuring cross section behavior these detectors will have an electrode spacing in the vicinity of about 1 mm., and the polarizing voltage will range from about 50 to about 150 volts.

The spaced-

apart electrodes

10 and 12 are made from stainless steel, brass, bronze, or any other suitable electrically conductive, gas-impermeable substance capable of maintaining structural strength and exhibiting relative inertness when exposed to the usual gaseous substances at elevated temperatures of 300 C. or above. Cell wall 14 is made from an electrically nonconductive substance which is gas-impermeable and which has chemical inertness and structural strength under these same conditions, polytetrafluoroethylene compounded with fillers (e.g., powdered glass, carbon, refractories, etc.) being typical. However, a highly preferred material of construction for use in making the cell walls and other electrically insulated parts of the detector cells of this invention is boron nitride. Boron nitride is a machinable ceramic having good structural and chemical inertness properties at temperatures far in excess of 300 C. It is a good thermal conductor and an outstanding electrical insulator. Moreover, it makes a very tight seal against metals, even against the polished metal surfaces of the electrodes and thus renders the cells leakproof. Consequently, the use of boron nitride in the construction of ionization detector cells constitutes a preferred embodiment of this invention-its combination of properties contributes materially to the durability and usefulness of the entire unit.

The ionization detector cell of FIG. 3 utilizes cylindrical geometry. The cell involves cylindrical electrode 30 supported within and concentrically aligned with cup-shaped electrode 32 thereby forming an annular gap 34 therebetween. In the embodiment shown, a thin Ni B-source 36 is supported on the outer cylindrical surface of electrode 30 and another thin Ni B-source 38 is supported on the inner cylindrical surface of electrode 32, B-

sources

36 and 38 preferably being plated directly upon the respectiveelectrode surfaces. Electrode 30 is supported axially within the cell by means of threaded stud support 40 which extends outwardly through an insulating flange 42 enclosing the end of the cell,.Stud 40 passes through the center of flange 42 and thereby provides an external electrical connectionfor electrode 30. Thus

electrodes

30 and 32 are in spaced-apart ionization detection relationship and are physically joined only by flange 42 which, of course, is made from a suitable electrical nonconductor, such as those referred to hereinabovc. Gas inlet tube 46 and gas outlet tube 48 transport gas into and out of the cell through the annular gap 34. Threads on stud 40 provide a convenient means of securing electrode 30 to flange 42 by means ofa threaded

nut Electrodes

30 and 32 are maintained at opposite polarities, electrode 30 preferably, but not necessarily, serving as the anode. For cross section detection, gap 34 will be in the order of about 1 mm., and the polarizing potential will range from about 50 to about I50 volts either DC or pulsating DC. For electron capture detection, gap 34 will be approximately 1 cm., the polarizing potential being from between about zero and about 50 volts, either DC or pulsating DC.

Pin cup geometry is depicted in FIG. 4. The cell is composed of cathode 60, anode 62, flange 64, gas inlet tube 66, gas outlet tube 68 and B-emitter 70. Flange 64 establishes a gas-impermeable union between the electrodes and therefore is made from a suitable electrically nonconductive material (e.g., polytetrafluoroethylene or, preferably, boron nitride). Anode 62 is preferably provided with threads 72 so as to enable precise adjustments in the extent to which anode 62 penetrates into the cell. In the embodiment shown, B-emitter 70 is in the form of a thin cylindrical foil of Ni (preferably plated on a thin backing foil as described hereinabove) mounted against the interior surfaces of cathode 60, the length of the cylindrical foil being such as to extend from about the inlet end of the cell to somewhere near its midpoint. It will be understood of course that the dimensions and positioning of the cell elements may be varied depending, for example, on whether the cell is to measure cross section behavior or electron capture. Thus for measuring cross section behavior the gap between anode 62 and cathode 60 will range from about 0.5 mm. to about 2 mm. with potentials of from about 50 to about 300 volts. When used for electron capture operation this gap will be from about 0.5 cm. to about 2 cm., at potentials of from between zero and about I50 volts.

The referred embodiment of this invention depicted in FIG. 5 possesses attributes and features of cylindrical geometry and pin cup geometry. In this embodiment the cell is composed of a cup-shaped cathode 80, an adjustable anode 81 axially aligned therewith and penetrating through threaded orifice 82 into the cylindrical chamber 83. Chamber 83 is defined in its upper portion by the walls of cathode and in its lower portion by spacer 84 and wafer 85 through which anode 8] passes. In this device the ionization source 86 is composed of a Ni foil (preferably 10 millicuries of Ni plated onto a 0.02- inch gold foil) wrapped around the inner circumference of cathode 80 so that the thin film or plate of Ni directs its B- emissions into chamber 83. Alternatively, the film of Ni may be plated on the interior cylindrical surface of cathode 80 V which has previously been given an undercoating film of gold plating. In the case where a discrete foil is employed, the foil is held in place by means of spacer 84 whose internal diameter is slightly less than the internal diameter of cathode 00. Gas is introduced into chamber 83 via conduit 87 and leaves the cell via orifice tlti, chamber 39 and conduit 90. Cathode 80, spacer FM and wafer 05 are enca ted by insulators 9i and 92 which in turn are encased by

cylindrical body members

93, 94 and 95. Electrical connection to cathode 80 is accomplished via rod 96 which is threaded on its inner and so as to fit into a threaded recess in the cathode and which is provided at its outer end with connector means indicated generally by the numeral 97. By the same token. electrical connection to anode Bl is effected via wafer 85 and rod 98 which is similarly threaded at its inner end and equipped at its outer end with connector means indicated generally by the numeral 99. Inasmuch as this cell is adapted for use at relatively high temperatures (e.g., at the present time, to temperatures as high as 300 C.) all of the members of the cell serving at least in part as electrical insulators (e.g., spacer 8d,

insulators

9t, 92, 100 and MI) are made from ceramic materialmost preferably boron nitride for reasons noted her inabove-whereas all of the metallic members (except ionization source 86) are made from stainless steel, 303 SS being particularly suitable. Moreover, a 50 or I watt cylindrical heater cartridge 1101 is inserted into a cylindrical recess ll02 extending upwardly from the bottom of body member 95 near its periphery. A temperature limit switch 103 to cut off the heater if temperatures become excessive is also provided and similarly positioned.

When used as a higlrternperature electron capture detector, the device of FIG. 5 is operated at a potential of from between zero to about I50 volts (DC or pulse). For such usage chamber 83 has an inner diameter, d. of 0.5 inch and a length, L, of 0.75 inch, the height h, of ionization source 06 being 0.5 inch and the diameter of the upper end of anode 81 being from 1/32 to A inch. For optimum performance it is desirable to adjust anode 81 so that its upper end is slightly below the horizontal plane defined by the lower edge of ionization source 86. Nevertheless, excellent results have been achieved when the top of anode 81 is from %-ll'lCI'l above to %-inch below said plane. In this connection, body member 95 is readily removed from the unit so as to provide ready access to the threaded adjustable anode for making adjustments to optimize performance under varying conditions of operation.

When designed for use as a cross section detector, the device of FIG. 5 is operated at a potential of from about 50 to about 300 volts, d is about 0.5 inch, L is about 0.75 inch, h is about 1 1/16 inch, and the diameter of the upper end of anode 81 is from about l5/32 to it; inch.

To illustrate some of the advantageous features of the detectors of this invention recourse was had to a series of comparative determinations of the relative efticiencies of Ni and of tritium as electron sources. These measurements were all made in the same cell a pin cup detector) at an applied potential of I50 volts. The tritium sources were a series offoils in which different measured quantities of tritium were occluded into titanium backed by stainless steel. The Ni sources were a series of gold foils onto which were deposited varying measured quantities of this nickel isotope. The criterion of effectiveness or efficiency was the standing ion current in nitrogen gas at the applied potential. The results of these determinations are shown in FIG. 6. inspection of these data will show, for example, that it requires 50 millicuries ofa typical tritium source to produce the same standing ion current produced by only 10 millicuries of Ni. Inasmuch as an electron source at a given level of standing ion current generally produces an equivalent electron capture sensitivity, these results establish beyond peradventure that the ionization detection cells of this invention are markedly superior to the best tritium-containing cells now in use.

Other experimental work has established other important advantageous features of this invention. For example, after 422 hours of operation at 300C. a detector cell as depicted in FIG. 5 was found to release no detectable amount of radioae tivity via the exit gas, the amount, if any, of radioactivity emitted being less than l l0 microcuries-the limitof the .hibited by the Ni sources ofthis invention, Kohn et al., (J. of

QC, Aug. 1965 pp. 287-288) have vividly demonstrated that tritium sources exhibit an onerous loss of radioactivity via the exit gas at their normal operating temperatures, i.e., 150 C. to 225C.

Additional experimental work has shown that the Ni' sources, when contaminated with such materials as substrate oils or high-boiling samples, can be safely cleaned and restored to peak efficiency by washing with any of a wide variety of suitable nonacid solvents (e.g. alcoholic KOH) without loss of radioactivity.

The relatively long halflife of Ni (85 years) is another advantage in its use pursuant to this invention.

Still another advantage is that Ni is relatively free of stochastic electrical noise-i.e., it has a high degree of con stancy in its emission of Bparticles. It has been found that plated Ni sources are consistently as good as or better in this respect than the best tritiated sources.

FIG. 7 is a high quality chromatogram obtained from routine operation of a laboratory gas chromatograph equipped with the preferred detector depicted in FIG. 5. The operating conditions and materials used were:

Carrier Gas 5 ercent CH, in Argon I00 mLIminute flow rate 40V (8 microseconds on microseconds off) Pulse Voltage It will be readily apparent to those skilled in the art that the chromatogram of FIG. 7 obtained in an instrument with a Ni B-emitter is equal to or superior to the results obtainable with the best tritium fl-sources. No such chromatogram could be obtained routinely and safely with any detector, operated at the conditions employed, other than a detector of this invention.

As noted above, Ni is readily plated upon a variety of metallic substrates and this enhances its utility as a B-emitter for use in the cells of this invention. It is especially preferred however to plate the Ni upon a noble metal substrate (e.g., platinum or gold) as this simplifies recovery or reclamation of the nickel isotope. This is readily accomplished by simply dissolving the Ni away from the noble metal substrate in a suitable mineral acid such as hydrochloric acid, sulfuric acid, or the like.

The deposition of a thin plate of Ni upon one or more electrodes of the cell is of particular advantage as compared to the use of radioactive foils. In the first place, foils are flimsy and are difficult to keep in place, especially when the apparatus is subjected to mechanical vibration or physical shock as may be encountered for example during shipment of the apparatus or during its use under severe environmental conditions. Such conditions present the possibility of the :foil causing a short circuit within the cell. In contrast, a thin film of Ni upon a rigid or at least nontlimsy substrate affords considerably greater mechanical stability. Secondly, the plating of Ni onto the electrode enables the formation of a highly uniform, smooth coating which contributes appreciably to the uniformity of emission from all surfaces so plated. Furthermore, this procedure permits very accurate control of the gap in cross section operation where the gap is inherently quite small and where nonuniformity of the gap can be a serious problem.

Generally speaking, the amount of Ni employed in a cell of I emitters pursuant to this invention is not restricted to the particular cell geometries referred to above. The principles of this invention extend to, and the advantages of this invention are realized by the utilization of a Ni B-emitter in any suitable type of cell construction although to date the best mode contemplated for the practice of the invention is that presented with reference to FIG. 5. It will be further understood and appreciated that ionization within the gas contained in the present detector cells may be enhanced by the presence therein of gaseous elements contributing metastable energy transfers, e.g., argon.

What is claimed is:

I. Ionization detection analysis apparatus comprising:

a. means defining a chamber having entrance and exit port means communicating with said chamber for directing gaseous matters through said chamber;

b. heating means for maintaining said gaseous matter within said chamber at a temperature of at least about 225 C;

c. electrode means disposed in said chamber in ionization detection relationship; and

d. a nickel-63 radioactive source positioned in said chamber to emit B particles into the gaseous matter when such matter is in ionization detection proximity-to said electrodes.

2. The apparatus of claim 1 having two electrodes arranged in an electron capture mode wherein said electrodes are spaced apart by a distance of about 0.5 cm., to about 2 cms. and including means to impress a polarizing potential of up to about l50 volts'across said electrodes.

3. The apparatus of claim 1 having two electrodes arranged in a cross section detector mode wherein said electrodes are spaced apart by a distance of from about ()5 mm. to about 2 mms. and including means to impress a polarizing potential of from about 50 to about 300 volts across said electrodes.

4. The apparatus of claim 1 wherein said means defining said chamber includes a detector body at least a portion of which is composed of boron nitride.

5. The apparatus of claim 1 wherein said electrode means comprises a pair of electrodes and wherein said nickel-63 source is disposed over a portion of one of said electrodes.

6. The apparatus of claim 5 wherein said nickel63 is plated over a noble metal.

7. An electron capture ionization detection apparatus comprising:

a. a detector body having a chamber defining in part a cylindrically shaped cathode member, said detector body having entrance and exit port means communicating with said chamber for directing gaseous matter through said chamber;

c. a nickel-63 radioactive source disposed about the inner circumference of said cathode member and positioned to emit [3 particles into said chamber; and

d. an anode member disposed within said chamber which anode member does not penetrate the plane defined by the edge of said nickel-63 source.

8. The detection apparatus of claim 7 including a spacer of electrically insulating material defining the wall of said chamber adjacent said cathode, said spacer having an internal passage with an internal diameter less than the internal diameter of said cathode.

9. The detection apparatus of claim 8 wherein said spacer is composed of boron nitride.

10. An electron capture ionization detection apparatus comprising:

a. a hollow cylindrical chamber defined at one endby-a cupshaped stainless steel cathode and in part by a cylindrical boron nitride cell wall of lesser diameter than said cathode abutting the open edge of said cup-shaped cathode;

bv an anode at the opposite end of said cylinder from said cathode and which anode does not penetrate the plane formed by said edge of said cathode;

. from about 5 to about 50 millicuries of nickel-63 disposed around the inner circumference of said cathode, the nickel-63 being thereby positioned so as to emit [3 particles into said chamber;

d. entrance and exit port means permitting gaseous matter to enter and to leave said chamber;

means for maintaining the temperature within said chamber at a selected elevated temperature of at least 225 C; and

f. means for impressing a polarizing voltage across said cathode and anode.

11. In combination with a gas chromatograph wherein gaseous sample components are eluted from a chromatographic column with a carrier gas, an electron capture ionization detector capable of analysis of said chromatograph effluent at temperatures above 225 C. which comprises:

a. a detector body defining a chamber;

b. a pair of electrodes in spaced-apart ion detection relationship in said chamber;

c. means for conducting the gas sample components from said chromatographic column to said chamber;

(1. a nickel-63 radioactive source positioned to emit B particles into said gas sample components eluting into said chamber; and

e. means to maintain an elevated temperature above 225 C.

in said chamber.

12. A method for analyzing the effluent of a gas chromatograph at elevated temperatures which comprises:

I a. heating the effluent of a chromatographic column to an elevated temperature in excess of 225 C.;

b. conducting said heated effluent to a zone of polarized potential maintained at a temperature greater than 225 C.;

c. ionizing said effluent with beta particle emissions from a nickel-63 source while said effluent is in said polarized potential zone; and

d. measuring the fluctuation in ion current through the region of polarized potential.

Claims

2. The apparatus of claim 1 having two electrodes arranged in an electron capture mode wherein said electrodes are spaced apart by a distance of about 0.5 cm., to about 2 cms. and including means to impress a polarizing potential of up to about 150 volts across said electrodes.
3. The apparatus of claim 1 having two electrodes arranged in a cross section detector mode wherein said electrodes are spaced apart by a distance of from about 0.5 mm. to about 2 mms. and including means to impress a polarizing potential of from about 50 to about 300 volts across said electrodes.
4. The apparatus of claim 1 wherein said means defining said chamber includes a detector body at least a portion of which is composed of boron nitride.
5. The apparatus of claim 1 wherein said electrode means comprises a pair of electrodes and wherein said nickel-63 source is disposed over a portion of one of said electrodes.
6. The apparatus of claim 5 wherein said nickel-63 is plated over a noble metal.
7. An electron capture ionization detection apparatus comprising: a. a detector body having a chamber defining in part a cylindrically shaped cathode member, said detector body having entrance and exit port means communicating with said chamber for directing gaseous matter through said chamber; b. heating means for maintaining said gaseous matter within said chamber at a temperature of at least about 225* C; c. a nickel-63 radioactive source disposed about the inner circumference of said cathode member and positioned to emit Beta particles into said chamber; and d. an anode member disposed within said chamber which anode member does not penetrate the plane defined by the edge of said nickel-63 source.
8. The detection apparatus of claim 7 including a spacer of electrically insulating material defining the wall of said chamber adjacent said cathode, said spacer having an internal passage with an internal diameter less than the internal diameter of said cathode.
9. The detection apparatus of claim 8 wherein said spacer is composed of boron nitride.
10. An electron capture ionization detection apparatus comprising: a. a hollow cylindrical chamber defined at one end by a cup-shaped stainless steel cathode and in part by a cylindrical boron nitride cell wall of lesser diameter than said cathode abutting the open edge of said cup-shaped cathode; b. an anode at the opposite end of said cylinder from said cathode and which anode does not penetrate the plane formed by said edge of said cathode; c. from about 5 to about 50 millicuries of nickel-63 disposed around the inner circumference of said cathode, the nickel-63 being thereby positioned so as to emit Beta particles into said chamber; d. entrance and exit port means permitting gaseous matter to enter and to leave said chamber; e. means for maintaining the temperature within said chamber at a selected elevated temperature of at least 225* C; and f. means for impressing a polarizing voltage across said cathode and anode.
11. In combination with a gas chromatograph wherein gaseous sample components are eluted from a chromatographic column with a carrier gas, an electron capture ionization detector capable of analysis of said chromatograph effluent at temperatures above 225* C. which comprises: a. a detector body defining a chamber; b. a pair of electrodes in spaced-apart ion detection relationship in said chamber; c. means for conducting the gas sample components from said chromatographic column to said chamber; d. a nickel-63 radioactive source positioned to emit Beta particles into said gas sample components eluting into said chamber; and e. means to maintain an elevated temperature above 225* C. in said chamber.
12. A method for analyzing the effluent of a gas chromatograph at elevated temperatures which comprises: a. heating the effluent of a chromatographic column to an elevated temperature in excess of 225* C.; b. conducting said heated effluent to a zone of polarized potential maintained at a temperature greater than 225* C.; c. ionizing said effluent with beta particle emissions from a nickel-63 source while said effluent is in said polarized potential zone; and d. measuring the fluctuation in ion current through the region of polarized potential.