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A s <br /> ON <br /> Tracer Research Corporation <br /> � sa+ <br /> r QUALITY ASSURANCE/QUALITY CONTROL PROCEDURES <br /> i <br /> Tracer Research Corporation's normal quality assurance <br /> !f� procedures were followed in order to prevent any cross- <br /> ?: ^ contamination of soil gas samples. <br /> ' Steel probes are used only once during the day and then <br /> washed with high pressure soap and hot water spray or <br /> W steam-cleaned to eliminate the possibility of cross- <br /> contamination. Enough probes are carried on each van to <br /> avoid the need to revise any during the day. <br /> Probe adaptors (steel reducer and tubing) are used once <br /> •- during the course of the day and cleaned at the end of each <br /> working day by baking in the GC oven. The tubing is <br /> replaced 'periodically as needed during the job to insure { <br /> cleanliness and good fit. <br /> Silicone tubing (connecting the adaptor to the vacuum pump) <br /> is replaced as needed to insure props- sealing around the <br /> syringe needle. This tubing does not directly contact soil <br /> gas .samples. <br /> x <br /> 1 Glass syringes are usually used for only one sample per day <br /> and. are washed and baked out at night. If they must be <br /> j used twices. they are purged with carrier gas (nitrogen) and <br /> baked out between probe samplings. <br /> T. <br /> �,..� Septa through which soil. gas samples are injected into the <br /> chromatograph are .replaced on a daily basis to prevent <br /> :. <br /> escolumn'. <br /> possible gas leaks from the chromatographii <br /> f Analytical instruments are calibrated each day by .the use <br /> of chemical standards prepared in water by serial dilution <br /> from commercially available pure chemicals. - Calibration - -- <br /> checks are also run after- approximately every five soil <br /> gas sampling locations. <br /> f - 2 ce subsampl-ing syringes are checked for--contamination - <br /> ' prior to sampling each day by injecting nitrogen carrier. <br /> gas into the gas chromatograph. <br /> Prior to samp.ling ..each day, 'system blanks are runtocheck <br /> the sampling apparatus (probes adaptor, 10 cc syringe) for <br /> contaminat.ion. by drawing ambient air' frcm above <br /> ground <br /> through the system and comparing the analysts to a ton- <br /> 'i �r,r currently .sampled air analysis. <br /> 5 <br />