Ion mobility spectrometer system with improved specificity

Claim 2

In an ion mobility spectrometer wherein a sample gas or vapor having at least one constituent to be detected and a carrier gas are injected into a reaction chamber thereof, and wherein the sample gas contains contaminants which reduce the specificity of the ion mobility spectrometer to the at least one constituent to be detected, an improvement characterized by: at least one reagent source for introducing a reagent into the carrier gas prior to being injected into the ion mobility spectrometer, and a reagent having a higher proton affinity, electron affinity, or acidity than said contaminants, a lower proton affinity, electron affinity, or acidity than said at least one constituent to be detected, and which does not cluster with water disposed in said reagent source.

Claim 3

The ion mobility spectrometer of claim 1 wherein said reagent is selected from a group which includes ketones, carbonyl or phosphoryl compounds, and halogenated compounds.

Claim 4

The ion mobility spectrometer of claim 2 wherein said reagent is acetone.

Claim 5

The ion mobility spectrometer of claim 1 wherein said reagent is carbon tetrachloride.

Claim 6

The ion mobility spectrometer of claim 1 wherein said at least one reagent source is two reagent sources, one of said reagent sources having said reagent disposed therein and the other of said reagent sources having a different reagent.

Claim 7

The ion mobility spectrometer of claim 5 wherein said reagent is acetone and said different reagent is carbon tetrachloride.

Claim 8

The ion mobility spectrometer of claim 1 wherein said ion mobility spectrometer includes a membrane interface separating the sample gas from the carrier gas to reduce the quantity of contaminants in the sample from being injected into the ion mobility spectrometer.

Claim 9

The ion mobility spectrometer of claim 7 wherein said membrane interface is selectively permeable to said at least one constituent of the sample to be detected.

Claim 10

The ion mobility spectrometer of claim 1 wherein said ion mobility spectrometer has a carrier conduit for conveying said carrier gas thereto said reagent source comprises at least one nonporous container for holding said reagent, said container having at least an output aperture; means for coupling the output aperture of said container to said carrier conduit; a permeable membrane interposed between the reagent in said container and the carrier gas in said carrier conduit for transmitting said reagent to said carrier gas at a predetermined rate; and means for controlling the temperature of said reagent source.

Claim 11

The ion mobility spectrometer of claim 9 wherein said reagent is selected from the group including ketones, carbonyl, or phosphoryl compounds, and halogenated compounds.

Claim 12

The ion mobility spectrometer of claim 10 wherein said reagent is acetone.

Claim 13

The ion mobility spectrometer of claim 9 wherein said permeable membrane is at least one sheet of polypropylene disposed over said output aperture.

Claim 16

The method of claim 13 wherein said step of ionizing said reagent/carrier/sample mixture forms stable dimer ions.

Claim 17

The method of claim 13 wherein said step of mixing mixes with said carrier gas a reagent selected from the group including ketones, carbonyl, and phosphoryl compounds.

Claim 18

The method of claim 15 wherein said step of mixing mixes acetone with the carrier gas.

Claim 19

The method of claim 13 wherein said at least one reagent comprises said at least one reagent plus a second reagent.

Claim 20

The method of claim 17 wherein said at least one reagent is acetone and said second reagent is carbon tetrachloride.

Claim 21

The method of claim 13 wherein said step of combining comprises the steps of: flowing said sample gas over one surface of a permeable membrane interface operative to selectively transmit the constituents of the sample gas to be detected; and flowing said reagent/carrier mixture over the opposite surface of said membrane interface to combine the transmitted constituents of the gas sample with said reactant/carrier mixture to form said reactant/carrier/sample mixture.

Claim 22

An ion mobility spectrometer system comprising: an ion mobility spectrometer having a reaction chamber, a contiguous drift chamber, an injection grid separating said reaction and drift chambers, ionization means disposed in said reaction chamber, a collector electrode disposed in said drift chamber opposite said injection electrode and means for generating a electrostatic field gradient across said contiguous reactant and drift chambers; pump means for supply a continuous flow of a carrier gas though said reaction and drift chambers means for injecting a sample gas having at least one constituent to be detected into the carrier gas flow supplied to said reaction chamber; reagent source means for injecting at least one reagent into the flow of carrier gas supplied to said reaction chamber, said reagent having a proton affinity, electron affinity, or acidity greater than water an less the constituents of the sample gas to be detected and which does not cluster with water; means for periodically generating an injection signal biasing said injection grid for a short period of time to transmit a portion of the ions generated in said reaction chamber to said drift chamber; amplifier means for generating an ion signal indicative of the number of ions collected by the collector electrode; and an electronic processing unit responsive to the time differential between said injection signal and said ion signals for generating a signature indicative of the characteristics of the sample gas.

Claim 23

An ion mobility spectrometer system comprising: an ion mobility spectrometer having a reaction chamber, a contiguous drift chamber, an injection grid separating said reaction and drift chambers, ionization means disposed in said reaction chamber, a collector electrode disposed in said drift chamber opposite said injection electrode and means for generating a electrostatic field gradient across said contiguous reactant and drift chambers; pump means for supply a continuous flow of a carrier gas though said reaction and drift chambers means for injecting a sample gas having at least one constituent to be detected into the carrier gas flow supplied to said reaction chamber; reagent source means for injecting at least one reagent into the flow of carrier gas supplied to said reaction chamber, said reagent having a proton affinity, electron affinity, or acidity greater than water an less the constituents of the sample gas to be detected and which does not cluster with water; means for periodically generating an injection signal biasing said injection grid for a short period of time to transmit a portion of the ions generated in said reaction chamber to said drift chamber; amplifier means for generating an ion signal indicative of the number of ions collected by the collector electrode; and an electronic processing unit responsive to the time differential between said injection signal and said ion signals for generating a signature indicative of the characteristics of the sample gas.

Claim 24

The ion mobility spectrometer system of claim 20 wherein said pump means comprises: a pump for recirculating said carrier gas through said reaction and drift chambers, and a filter for removing at least water, ammonia, and oxides of nitrogen from said carrier gas.

Claim 25

The ion mobility spectrometer system of claim 20 wherein said pump means comprises: a pump for recirculating said carrier gas through said reaction and drift chambers, a filter for removing water from said recirculation carrier gas; and means for controlling the flow rate of said carrier gas through said reaction and drift chambers.

Claim 26

The ion mobility spectrometer system of claim 20 wherein said reagent source means comprises: at least one nonporous container having an outlet aperture, said container containing at least one reagent; means for coupling the outlet aperture of said container to said flow of carrier gas to said reaction chamber; and a permeable membrane interposed between said outlet aperture and said flow of carrier gas for transmitting said reagent to said carrier gas at a predetermined rate.

Claim 27

The ion mobility spectrometer system of claim 20 wherein said reagent form stable dimer ions when ionized by said means for ionizing.

Claim 28

The ion mobility spectrometer system of claim 24 wherein said reagent is acetone.

Claim 29

The ion mobility spectrometer system of claim 20 wherein said at least one reagent is two reagents and wherein one of said two reagents is acetone and the other of said two reagents is carbon tetrachloride.

Claim 30

The ion mobility spectrometer system of claim 20 wherein said means for injecting a sample gas to said flow of carrier gas comprises: a permeable membrane operative to selectively transmit at least one constituent of the sample to be detected; means for directing a flow of said sample over one surface of said permeable membrane; means for directing the flow of carrier gas over the opposite surface of said permeable membrane to mix the carrier gas with the constituents of the sample permeated through said peremeable membrane; and means for conducting the mixture of said carrier and said permeated constituents of said sample gas to said reaction chamber.

Claim 31

The ion mobility spectrometer system of claim 24 wherein said permeable membrane aids in the removal of water, ammonia and oxides of nitrogen from the sample.

Claim 32

In an ion mobility spectrometer wherein a sample having at least one constituent to be detected and a carrier gas are injected into the reaction chamber of the ion mobility spectrometer and wherein the sample contains contaminants including water which reduce the specificity of the ion mobility spectrometer, an improvement for increasing the specificity of the ion mobility spectrometer characterized by: reagent source means for mixing with the carrier/gas at least one reagent having a proton affinity greater than water and less than the proton affinity of the constituents of the sample to be detected and which does not cluster with water to produce a reagent/carrier mixture; a permeable mebrane selectively permeable to the at least one constituent of the sample to be detected; means for directing a flow of the sample onto one surface of said permeable membrane; means for directing a flow of said reagent/carrier mixture onto the opposite surface of said permeable membrane to mix said reagent and carrier gas with the constituents of the sample permeated therethrough; and means for conducting said reagent/carrier mixture and the permeated constituents of the sample into the reaction chamber of said ion mobility spectrometer.

Claim 33

In an ion mobility spectrometer wherein a sample having at least one constituent to be detected and a carrier gas are injected into the reaction chamber of the ion mobility spectrometer and wherein the sample contains contaminants including water which reduce the specificity of the ion mobility spectrometer, an improvement for increasing the specificity of the ion mobility spectrometer characterized by: reagent source means for mixing with the carrier/gas at least one reagent having a proton affinity greater than water and less than the proton affinity of the constituents of the sample to be detected and which does not cluster with water to produce a reagent/carrier mixture; a permeable mebrane selectively permeable to the at least one constituent of the sample to be detected; means for directing a flow of the sample onto one surface of said permeable membrane; means for directing a flow of said reagent/carrier mixture onto the opposite surface of said permeable membrane to mix said reagent and carrier gas with the constituents of the sample permeated therethrough; and means for conducting said reagent/carrier mixture and the permeated constituents of the sample into the reaction chamber of said ion mobility spectrometer.

Claim 34

The ion mobility spectrometer of claim 29 wherein said reagent forms stable dimer ions.

Claim 35

The ion mobility spectrometer of claim 29 wherein said reagent is selected from the group including ketones, and carbonyl or phosphoryl compounds.

Claim 36

The ion mobility spectrometer of claims 30 or 31 wherein said reagent is acetone.

Claim 37

The ion mobility spectrometer of claim 29 wherein said source means mixes said at least one reagent and a second reagent with said carrier gas.

Claim 38

The ion mobility spectrometer of claim 33 where said at least one reagent is acetone and said second reagent is carbon tetrachloride.