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QUALITY CONTROL REPORT <br /> METHOD BLANK RESULTS A method blank (MB) is a laboratory generated sample free <br /> of any contamination The method blank assesses the degree to which the <br /> laboratory operations and procedures cause false-positive analytical results for <br /> your samples The method blank results associated with your samples are <br /> attached <br /> LABORATORY CONTROL SPIKES <br /> The LCS Program <br /> The laboratory control spike is a well characterized matrix (organic pure <br /> type II for water samples and contamination free sand for soil samples) <br /> which is spiked with certain target parameters and analyzed In duplicate <br /> at approximately 10% of the sample load in order to assure the accuracy <br /> and precision of the analytical method The results of the laboratory <br /> control spike associated with your samples are attached <br /> Accuracy is measured using percent recovery, i e <br /> (measured concentration) <br /> Percent Recovery — ---------------- -------- x 100 <br /> (actual concentration) <br /> • Precision is measured using the relative percent difference (RPD) from <br /> duplicate tests, i e <br /> % Recovery of Spike - Recovery of Spike (2) <br /> RPDa --- ---------- ------ - --- --- ---- ------------ - -- - - --- -- x 100 <br /> (% Recovery of Spike(l) + % Recovery of Spike(2} )/2 <br /> Control limits for accuracy and precision are different for different , <br /> methods They may also vary with the different sample matrices They are <br /> based on laboratory average historical data and EPA limits which are <br /> approved by the Quality Assurance Department McLaren Analytical <br /> Laboratory reanalyzes samples if the precision or accuracy is out of <br /> acceptance control limits <br /> Z. <br /> McLaren <br /> (CN2330) <br />