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mes- <br /> " F <br /> QUALITY CONTROL REPORT <br /> r 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 11 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 d ------------------------ x 100 <br /> (actual concentration) <br /> Precision is measured using the relative percent difference (RPD) from <br /> duplicate tests, i.e.: <br /> I Recovery of Spike(l) - $ Recovery of Spike 2) <br /> RPD <br /> RPD -------------------- x 100 <br /> (� Recovery of Spike0) + % Recovery of Saike(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 /> McLaren <br /> - — (CN2239) . <br />