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Tracer Research Corporation <br /> 1 <br /> 5.2 Chromatographic System <br /> A Hewlett Packard 5890 Series H gas chromatograph,equipped with a flame <br /> ionization detector (FID) and a computing integrator, was used for the soil gas and <br /> groundwater analyses. Compounds were separated in the GC on a 6 foot by 118 inch <br /> outer diameter (OD) packed analytical column with chromosorb (OV101) as the <br /> stationary phase in a temperature controlled oven. Nitrogen was used as the carrier <br /> gas. The following paragraphs explain the GC and FID processes. <br /> GC Process <br /> The soil gas vapor is injected into the GC where it is swept through the <br /> ' analytical column by the carrier gas. The detector senses the presence of a component <br /> different from the carrier gas and converts that information to an electrical signal. The <br /> components of the sample pass through the column at different rates, according to <br /> their individual properties, and are detected by the detector. Compounds are <br /> identified by the time it takes them to pass through the column (retention time). <br /> FID Process <br /> The FID utilizes a flame produced by the combustion of hydrogen and air. <br /> When a component, which has been separated on the GC analytical column, is <br /> introduced into the flame, a large increase in ions occurs. A collector with a <br /> Pg <br /> olarizin voltage is applied near the flame and the ions are attracted and produce a <br /> current, which is proportional to the amount of the sample compound in the flame. <br /> The electrical current causes the computing integrator to record a peak on a <br /> chromatogram. By measuring the area of the peak and comparing that area to the <br /> ' integrator response of a known aqueous standard, the concentration of the analyte in <br /> the sample is determined. <br /> 5.3 Analyses <br /> Subsamples (duplicate injections) of the soil gas samples were injected into <br /> the GC in volumes of 500 to 1000 microliters (ul). Subsamples of the water <br /> headspace samples were also injected into the GC in volumes ranging from 100 to <br /> 1000 ul. <br /> May 22. 1992 Page 4 1-92-358 <br /> t <br />