Sampling and detection of trace gas species by optical spectroscopy
AssigneeSymyx Technologies, Inc.
InventorPejun Cong
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Abstract
The present invention discloses a method for improving the speed and sensitivity of optical spectroscopic techniques for remote detection of trace chemical species in a carrier gas. The disclosed method can be applied to any optical spectroscopic detection technique whose sensitivity decreases as the total pressure of the sample decreases. The method employs an inert and non-absorbing buffer gas to supplement the pressure exerted by the carrier gas. This ensures that the total pressure of the sample, and hence sensitivity of the detection technique, remains high. The method is especially useful when measuring concentration of chemical species produced at small rates, and therefore should prove useful for rapid serial screening of combinatorial libraries of compounds.
Claims42
A method of improving the speed and sensitivity of remote detection of an analyte using an optical spectroscopy technique, the method comprising:
- obtaining a sample gas containing the analyte from a remote source, the remote source having a pressure P.sub.o ;
- introducing the sample gas containing the analyte in a detection cell at a pressure lower than P.sub.o ;
- separately introducing a buffer gas in the detection cell at a rate faster than the sample gas containing the analyte so that the detection cell has a total pressure P;
- detecting the analyte using the optical spectroscopy technique, wherein the optical spectroscopy technique is four-wave mixing spectroscopy or a photothermal detection method and produces a signal that depends on P.
A method of improving the speed and sensitivity of detecting an analyte using an optical spectroscopy technique, the analyte contained in a carrier gas and obtained from a remote source at a pressure P.sub.o, the method comprising:
- evacuating a detection cell to a pressure less than P.sub.o ;
- introducing a buffer gas in the detection cell, the buffer gas having a partial pressure P.sub.B in the detection cell such that P.sub.B is less than P.sub.o ;
- inputting the carrier gas containing the analyte in the detection cell, wherein the carrier gas is introduced in the detection cell uniformly over a period of time at a rate slower than the buffer gas;
- obtaining signals using the optical spectroscopy technique while inputting the carrier gas containing the analyte, wherein a rate of change of the signals with respect to time is proportional to the amount of the analyte, and the optical spectroscopy technique is four-wave mixing or a photothermal detection method.
A method of screening a combinatorial library, the combinatorial library having a total number of member compounds equal to N, the method comprising:
- obtaining a gas sample associated with a member compound at a pressure P.sub.o ;
- introducing the gas sample in a detection cell at a pressure lower than P.sub.o ;
- separately introducing a buffer gas in the detection cell at a rate faster than the sample gas so that the detection cell has a total pressure P;
- detecting an analyte contained in the gas sample using an optical spectroscopy technique, wherein the optical spectroscopy technique is four-wave mixing spectroscopy or a photothermal detection method and produces a signal that depends on P;
- and
- wherein the amount of the analyte is an indicator of the performance of the member compound.
A method of screening a combinational library by remote detection of an analyte using an optical spectroscopy technique, wherein the analyte is contained in a carrier gas, the combinatorial library has a total number of member compounds equal to N, and the analyte and the carrier gas are obtained at a pressure P.sub.o, the method comprising:
- evacuating a detection cell to a pressure less than P.sub.o ;
- introducing a buffer gas in the detection cell, the buffer gas having a partial pressure P.sub.B in the detection cell such that P.sub.B is less than P.sub.o ;
- inputting the carrier gas containing the analyte in the detection cell, wherein the carrier gas is introduced in the detection cell uniformly over a period of time at a rate slower than the buffer gas;
- obtaining signals using the optical spectroscopy technique while inputting the carrier gas containing the analyte, wherein a rate of change of the signals with respect to time is proportional to the amount of the analyte, and the optical spectroscopy technique is four-wave mixing or a photothermal detection method;
- and
- wherein the amount of the analyte is an indicator of the performance of the member compound.
Dependencies are inferred from the claim text.