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QUALITY CONTROL REPORT <br />METHOD BLANK RESULTS: A method blank (Mf3) 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 />AccurLcy 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(1)- % Recovery of Spike (2) <br />RPD-----------------------------•------------------------ x 100 <br />(% Recovery of Spike(1)+ % Recovery of Spike(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 />(DC3-CN2565) <br />