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Tracer Rasaarch Corporation I <br /> i <br /> l <br /> 1 <br /> ANALYTICAL PROCEDURES <br /> .; One Varian 3300 gas chromatograph, equipped with a flame ionization detector <br /> (FID), was used for the sample analyses. The FID was used for the analysis of benzene, <br /> toluene, ethylbenzene, xylenes and total hydrocarbons. Separation of the FID compounds <br /> was achieved on a 3' by 1/8" OD packed column with OV-101 as the statio Lary phase and • <br /> nitrogen as a carrier gas. <br /> Volatiles detected in soil gas and groundwater were identified by chromatographic <br /> A retention time. Quantification of compounds was achieved by comparison of the detector <br /> response of the sample with'the response measured for calibration standards (external <br /> standardization). Instrument calibration checks were run periodically throughout the day <br /> as were system blanks to check for contamination in the soil gas sampling equipment. Air <br /> samples were also routinely analyzed to check for background levels in the atmosphere. <br /> Detection limits for the compounds of interest are a function of the injection volume <br /> as well as the detector sensitivity for individual compounds. Thus,the detection limit varies <br /> 9 with the sample size. Generally, the larger the injection size the greater the sensitivity. <br /> However, peaks for compounds of interest must be kept within the linear range of the <br /> 1e <br /> t„ analytical equipment. If any compound has a high concentration, it is necessary to use <br /> small injections, and in some cases to dilute the sample to keep it within iinear range. This <br /> .. may cause decreased detection limits for other compounds in the analyses. <br /> t <br /> The detection limits range down to approximately 0.05 ug/L for compounds screened <br /> R on the FID depending on the conditions of the measurement,in particular,the sample size. <br /> If any component being analyzed is not detected, the detection limit for that compound in <br /> that analysis is given as a "less than" value (e.g. <0.05 ug/L). Detection limits obtained <br /> from GC analyses are calculated from the current response factor,the sample size, and the <br /> estimated minimum peak size (area) that would have been visible under the conditions of <br /> the measurement. <br /> 61 <br />