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CRA MEMORANDUM Page 2 <br /> SAMPLE PRESERVATION AND HOLDING TIMES <br /> Sample holding time periods and preservation requirements are summarized in the analytical methods. All <br /> sample extractions and/or analyses were performed within the specified holding times. <br /> All samples were properly preserved and cooled after collection. <br /> METHOD BLANK SAMPLES <br /> Method blank samples are prepared from a purified sample matrix and are processed concurrently with <br /> investigative samples to assess the presence and the magnitude of sample contamination introduced during <br /> sample analysis. Method blank samples are analyzed at a minimum frequency of one per analytical batch <br /> and target analytes should be non-detect. <br /> Method blanks were analyzed at the recommended frequency and all results were non-detect for the <br /> compounds of interest. <br /> SURROGATE COMPOUNDS-ORGANIC ANALYSES <br /> Individual sample performance for organic analyses was monitored by assessing the results of surrogate <br /> compound percent recoveries. Surrogate percent recoveries are reviewed against the laboratory developed <br /> control limits provided in the analytical report. <br /> All surrogate recoveries met the method criteria, demonstrating acceptable analytical efficiency for these <br /> analyses. <br /> LABORATORY CONTROL SAMPLE (LCS) <br /> The LCS analysis serves as a monitor of the overall performance in all steps of the sample analysis and are <br /> analyzed with each sample batch. The LCS percent recoveries were evaluated against method and <br /> laboratory established control limits. <br /> Laboratory control samples (LCS) were analyzed in duplicate for all parameters. All recoveries were within <br /> required control limits showing adequate analytical accuracy and precision. <br /> MATRIX SPIKE/MATRIX SPIKE DUPLICATE (MS/MSD) ANALYSES <br /> To assess the long term accuracy and precision of the analytical methods on various matrices, MS/MSD <br /> percent recoveries and relative percent differences (RPD) of the concentrations were determined. The <br /> organic MS/MSD percent recovery and RPD control limits are established by the laboratory. The inorganic <br /> control limits are defined by the methods and the "Guidelines",which require recoveries between 75 to <br /> 125 percent with RPDs less than 20 percent for water samples and 30 percent for soil samples. <br />