Method and apparatus for preconcentration for analysis purposes of trace constitutes in gases
First Claim
1. A method of preconcentrating trace constituents in a gas for subsequent analysis which comprises the steps of:
- A adsorbing at least one of the trace constituents onto a confined sorbent material for a predetermined period of time from a sample gas moving at a predetermined gaseous mass flow rate;
B confining said sorbent material in a sealed space which includes an inlet of a detector means for receiving said one trace constituent; and
C desorbing said one trace element from said sorbent material for a predetermined period of time into a carrier gas moving at a predetermined gaseous mass flow rate which is substantially less than the gaseous mass flow rate of said sample gas whereby the desorbed amount of said one trace constituent relative to said carrier gas that contains said desorbed trace constituent is substantially greater than the same amount of said one trace constituent relative to the portion of said sample gas that contained said trace constituent.
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Accused Products
Abstract
A preconcentrator for analyzing trace constituents in gases wherein a sample gas is introduced to a confined sorbent which thereafter is evacuated by a vacuum pump and a low-pressure carrier gas passes through the sorbent while it is desorbing, wherein the desorbed trace constituents are carried by the carrier gas to a detector that operates at low pressure such as a mass spectrometer. Because the mass of the carrier gas which carries the desorbed trace consituents to the detector is at a lower pressure and therefore has less density than the sample gas, the relative mass of trace constituents in the carrier gas is much greater than in the sample gas. The sample gas can be hot to assist desorption or a gas which reacts with trace constituents of interest to improve their detection. Valves located in the system between the sample gas intake, the carrier gas supply, the vacuum pump for the system and the detector operate to admit the sample gas, isolate the system, create a vacuum in the system, establish the sample gas flow, and to carry the trace consituents to the detector. Preconcentrators can be placed in parallel, whereby when one is desorbing and analyzing trace elements, the other is receiving the sample gas.
97 Citations
25 Claims
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1. A method of preconcentrating trace constituents in a gas for subsequent analysis which comprises the steps of:
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A adsorbing at least one of the trace constituents onto a confined sorbent material for a predetermined period of time from a sample gas moving at a predetermined gaseous mass flow rate; B confining said sorbent material in a sealed space which includes an inlet of a detector means for receiving said one trace constituent; and C desorbing said one trace element from said sorbent material for a predetermined period of time into a carrier gas moving at a predetermined gaseous mass flow rate which is substantially less than the gaseous mass flow rate of said sample gas whereby the desorbed amount of said one trace constituent relative to said carrier gas that contains said desorbed trace constituent is substantially greater than the same amount of said one trace constituent relative to the portion of said sample gas that contained said trace constituent. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An apparatus for preconcentrating trace constituents in a gas to facilitate their analysis which comprises:
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a sorbent material which is retained in a confined space and associated with means for selectively causing said sorbent material to adsorb or desorb said trace constituents; a sample gas source and valve for introducing said sample gas onto said sorbent material and means for selectively opening and closing said valve; a source of carrier gas connected to provide said carrier gas to said sorbent material; pumping means for selectively lowering the pressure in said confined space containing said sorbent material; a detector for detecting said trace constituents in said carrier gas; a confined passageway from said carrier gas source to said detector through said sorbent material, whereby when said sorbent material desorbs said trace constituents received from said sample gas they can be carried by said carrier gas to said detector at a pressure substantially less than the pressure of said sample gas, whereby the ratio of the density of said trace constituents to mass of said carrier gas is substantially increased relative to the ratio of the density of said trace constituents for a comparable mass of said sample gas. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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Specification