Rapid identification of nerve agents Sarin (GB) and Soman (GD) with the use of a field-portable GC/SAW vapor detector and liquid desorption front-end device

The nerve agents Sarin (GB) and Soman (GD) were detected at the picogram level with the use of a field-portable gas chromatograph with a surface-acoustic-wave detector (SAW). The instrument, although primarily a vapor detector, can be modified with a simple front-end thermostat attachment, which allows for small-volume liquid injections for the detection of analytes in the vapor-pressure range of 0.1–5.0 torr. A field analytical method was developed with the use of the analyte surrogates dimethyl methyl phosphonate (DMMP) and triethyl phosphate (TEP). These compounds were used as internal standards by which agents GB and GD can be detected, with the use of this liquid injection method coupled to the vapor detector. Actual tests on GB and GD were performed under the same conditions, but in a more closely monitored but less field-representative laboratory environment. GB was quantitated from a calibration plot that relates signal to mass via a conversion factor in less than 10 s. The turnaround time for the instrument between data sets was 2 min, depending on the exact parameters of the method.