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5.2 LABORATORY QUALITY CONTROL <br />The laboratories performing the analyses for the ASWAT program fol- <br />lowed the analytical procedures described in the ASWAT proposal (see <br />Appendix A). Additional laboratory QC for the air quality testing <br />program was provided by analyzing QC samples and comparing the results <br />with the actual test data. QC control samples consisted primarily of <br />blank samples and spiked samples. Some samples were also analyzed in <br />duplicate. The results of this QC testing were used to assess the <br />data's reproducibility, precision, and completeness by the methods <br />recommended in Guidelines. These methods and the results of the <br />assessment are briefly described below. <br />Data reproducibility is evaluated by calculating the relative percent <br />difference (RPD) of the results of replicate analyses according to the <br />formula given in EPA Handbook for Analytical Quality Control in Water <br />I nd Wastewater Labora o ries (June 1972, Section 6): <br />Where <br />RPD = (I + x <br />xIX21 x 100 <br />1 2 <br />x1 = first result <br />X2 = second result <br />Reproducibility was calculated for each analyte in each set of dupli- <br />cate samples. Mean RPD and standard deviation were also calculated <br />for the duplicate sets. <br />Duplicate analyses were performed on three ambient air samples and one <br />well sample. Each sample was analyzed for 10 VOCs specified in the <br />Guidelines. <br />PJ9 9390405.00D 5-6 Rev. 0 09/07/88 <br />Et11Con Associotes <br />