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r D Once the desired volume of sample has been collected, the sample is transferred to a loop of fused silica capillary tubing which is cooled to liquid argon temperature. This transfer is accomplished by rotating a six port valve so that Helium carrier gas passes through the sample loop and flushes the organic constituents onto the capillary loop. The original sample loop is heated with warm water to facilitate the transfer. This second cryofocussing step serves to focus the sample components into a very sharp band at the head of the fused silica capillary column. The fused silica capillary column is removed from the liquid argon and heated to initiate the chromatographic separation and GC/MS analysis. Fused silica capillary columns are used for their superior resolving power. The fact that they operate at relatively low flow rates (0.5 - 1.0 mL/min) permits interfacing the column directly to the ion source of the mass spectrometer. Chromatographic separations are carried out on a 30m x 0.25 mm i.d. fused silica column which is coated with a 0.25u film of a non -polar liquid phase (DB -5, J&W Scientific, Folsom, CA 95630). The Quantitative determinations of analyte concentrations are based on the column is temperature programmed from an initial temperature of -40 two high intensity, degrees C, held for 3 minutes, to a final temperature of 200 C at a rate passing it through a stainless steel of 7 degrees C per minute. The column is held at 200 C for 10 minutes to The mass spectrometer is operated in clear the analytical arrangement of valves system of any high boiling in the sampling and analytical components. The systems is such that constituents in the sample. during the analytical run and subsequent bakeout, zero air is flushed each chromatographic through the transfer system. In this way, both the sampling system and disc in real time during the analytical system are thoroughly purged prior to the introduction of the next sample. Quantitative determinations of analyte concentrations are based on the The capillary column is interfaced directly to the ion source of the HP two high intensity, 59708 quadrupole mass spectrometer by passing it through a stainless steel compound. conduit which is heated to 250 C. The mass spectrometer is operated in absolute compound the electron impact temperature of 200 C. mode at ionizing energy of 70 eV, with an ion source The quadrupole mass filter is scanned from m/z 35 - constituents in the sample. 200 at a rate of 125 amu/sec which insures at least 10 data points across based on reference each chromatographic peak. Mass and intensity data are stored on computer internal standard. disc in real time during the course of the chromatographic run. Quantitative determinations of analyte concentrations are based on the Instrument performance is checked daily with a series of instrument calibration standards and reference materials. The mass spectrometer is tuned using perfluorotributylamine and performance criteria are checked using bromofluorobenzene which is introduced through the gas chromatograph in order to monitor complete GC/MS system performance. Two certified reference standards are used to insure overall system sensitivity as well as measurement accuracy and precision. peak areas from the mass chromatograms for two high intensity, characteristic ions for each compound. Full scan data are available for absolute compound identification of constituents in the sample. Concentrations are calculated peak areas from the certified based on reference the peak standard, areas from the sample, and peak areas for the internal standard. Instrument performance is checked daily with a series of instrument calibration standards and reference materials. The mass spectrometer is tuned using perfluorotributylamine and performance criteria are checked using bromofluorobenzene which is introduced through the gas chromatograph in order to monitor complete GC/MS system performance. Two certified reference standards are used to insure overall system sensitivity as well as measurement accuracy and precision.