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r <br /> r �{ <br /> ON 01 - <br /> ,W- U <br /> Y <br /> r <br /> 5 <br /> 4 <br /> ;4 <br /> Y <br /> ward-Ctyde <br /> rpt Cons4iftan$3 <br /> 3.3 QUALITY ASSURANCE/QVALITY CONTROL <br /> h.7 " <br /> �~5 <br /> Travel/equipment blanks a^d blind duplicatzs were used to provide quality assurance and <br /> control. The analytical results for the blanks were below the detection limits of the TFH and <br /> mJ BTEX analyses. The analytical..results fir the December 31, 1991 blind duplicate sample <br /> (MW-23) were within twenty percent for each of the analytical parameters [(TFH (18%), <br /> benzene(15%)and ethylbenzene(0%)]of the original sample(MW-3). The field duplicate <br /> precision, ex}aessed as relative percent diffe'mnce (RPD), exceeded thirty percent for two <br /> compounds (toluene and total xylenes),. Since these rompciuitds were not found in one <br /> ¢„ sample in the duplicate pair, the detection limit can,be considered a maximum concentration i <br /> f which could be present in the samples. Toluene was found at 1.7 ppb, which .isover five <br /> Y-E . �F <br /> times the detection limit. Total xylenes were found at 1.8 ppb, which is twice the detection :.r. <br /> Imo. limit. Although the RPDs fcr toluene and total xylenes are relatively high, the validity of <br /> RPD as a quality control measurements decreases as concentrations approach the detection. <br /> limit, thus increasing the margin of error. The data is therefore not considered invalidated <br /> by Iow readings of these compounds in one sample of the sample pair. A Iack of detection s <br /> of these compounds in either the equipment blank or the method blank further suggests that ` <br /> laboratory or field contamination did not cause the difference reported results for the ! <br /> duplicate pair. The detection limit for each analysis is shown on the analytical report <br /> w (Appendix B): The chemical data assessed by the above review are considered adequate and ` z. <br /> Y <br /> valid for their intended use. <br /> r, x <br /> I,,✓ r ; b <br /> z <br /> %J41 91002369/MA 0Rt,(ART.QRP'r 02--:492 3-4 r <br /> 4' <br /> 1 <br />