Method and apparatus for improving the specificity of an ion mobility spectrometer utillizing sulfur dioxide dopant chemistry
AssigneeEnvironmental Technologies Group, Inc.
InventorsAllan T. Bacon, Jr., Julio A. Reategui
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Abstract
An improved ion mobility spectrometer (IMS) and method for operating the same which enables analysis of a specific acid gas analyte in a mixture of such gases when air is used as the carrier gas and the drift gas in the IMS. A controlled concentration of sulfur dioxide dopant is added to the air carrier gas stream prior to application of the carrier gas stream. In the IMS, the drift times of the ions generated from the doped air carrier gas differ from the drift times of the ions generated from the acid gas analyte, thereby enabling identification and quantification of the analyte.
Claims34
An improved method for operating an ion mobility spectrometer using air as a carrier gas and as a drift gas, said spectrometer comprising an analyzer cell having an inlet region, a reaction region, an ionization source in said reaction region, a shutter grid, a drift region, an ion current detector for detecting ions transiting said cell drift region, and means for measuring the transit times through said cell drift region of ions generated in said cell reaction region and released into said cell drift region through said shutter grid, the method comprising the steps of:
- applying a drift gas stream of air to said cell drift region;
- mixing sulfur dioxide with a carrier gas stream of air to create a doped carrier gas stream;
- introducing a test sample of gas into said analyzer cell inlet region;
- applying said carrier gas stream to said cell inlet region to carry said test sample into said cell reaction region;
- and
- measuring an ion current at said ion current detector at a time corresponding to the transit time through said cell drift region of ions generated by said test sample in said cell reaction region;
- whereby said sulfur dioxide dopant causes ions generated by said carrier gas stream in said cell reaction region to have transit times through said cell drift region which are different from the transit times through said cell drift region of ions generated by the test sample.
An improved method for operating an ion mobility spectrometer using air as a carrier gas and as a drift gas, said spectrometer comprising an analyzer cell having an inlet region, a reaction region, an ionization source in said reaction region, a shutter grid, a drift region, an ion current detector for detecting ions transiting said cell drift region, and means for measuring the transit times through said cell drift region of ions generated in said cell reaction region and released into said cell drift region through said shutter grid, the method comprising:
- introducing a test sample of gas into said analyzer cell inlet region;
- applying a carrier gas stream to said cell inlet region to carry said test sample into said cell reaction region;
- applying a drift gas stream of air to said cell drift region;
- mixing sulfur dioxide with said drift gas stream of air to create a doped drift gas stream for carrying product ions generated by said test sample in said cell reaction region into said cell drift region;
- and
- measuring a product ion current at said ion current detector at a time corresponding to the transit time through said cell drift region of said product ions;
- whereby said sulfur dioxide dopant causes ions generated by said drift gas in said cell reaction region to have transit times through said cell drift region which are different from the transit times through said cell drift region of ions generated by the test sample.
An ion mobility spectrometer for analyzing an acid gas in a test sample, comprising:
- an inlet region for inputting a test sample of gas;
- a reaction region in fluid communication with said inlet region;
- means for applying a carrier gas stream of air to said inlet region for carrying said test sample therefrom into said cell reaction region;
- doping means for introducing sulfur dioxide into said carrier gas stream of air;
- an ionization source in said reaction region for generating product ions from the test sample carried into the reaction region by said carrier gas;
- a drift region through which said product ions travel in accordance with a charge and molecular size characteristic;
- a shutter grid for selectively releasing said product ions from said reaction region into said drift region;
- an ion current detector for detecting product ions transiting said cell drift region;
- means for measuring a transit time through said cell drift region of product ions generated in said cell reaction region and released into said cell drift region through said shutter grid;
- and
- means for measuring an ion current detected by said cell ion current detector at a time corresponding to the drift time of ions generated from said analyte gas in said cell reaction region;
- whereby sulfur dioxide dopant introduced by said doping means causes ions generated by said carrier gas stream in said cell reaction region to have transit times through said cell drift region which are different from the transit times through said cell drift region of ions generated by the test sample.
An ion mobility spectrometer for analyzing an acid gas in a test sample, the spectrometer comprising:
- an inlet region for introduction of said test sample of gas, said inlet region having means for allowing a limited amount of said test sample to penetrate;
- a reaction region in fluid communication with said inlet region;
- an ionization source in said reaction region for generating product ions from the test sample carried into the reaction region by said carrier gas;
- a drift region through which said product ions travel in accordance with a charge and molecular size characteristic;
- a shutter grid for selectively releasing said product ions from said reaction region into said drift cell drift region;
- means for applying a drift gas stream of air to said to said drift region for carrying test sample having penetrated said membrane into said cell reaction region;
- means for introducing sulfur dioxide dopant to said carrier gas stream of air and to said drift gas stream of air;
- an ion current detector for detecting product ions transiting said cell drift region;
- and
- means for measuring the transit times through said cell drift region of product ions generated in said cell reaction region and released into said cell drift region through said shutter grid;
- means for measuring an ion current detected by said cell ion current detector at a time corresponding to the drift time of ions generated from said analyte gas in said cell reaction region to provide an ion current value;
- whereby said sulfur dioxide dopant causes ions generated by said carrier gas stream and drift gas stream in said cell reaction region to have transit times through said cell drift region which are different from the transit times through said cell drift region of ions generated by the test sample.
Dependencies are inferred from the claim text.