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CRA MEMORANDUM Page <br /> All initial calibration standards were analyzed at the required frequencies. All retention time, peak <br /> resolution, and linearity criteria were satisfied as specified in the methods. <br /> 5.0 Continuing Calibration - Organic Analyses <br /> GC/MS <br /> To ensure that instrument calibration for VOC analyses is acceptable throughout the sample analysis <br /> period, continuing calibration standards must be analyzed and compared to the initial calibration curve <br /> every 12 hours. <br /> The following criteria were employed to evaluate continuing calibration data: <br /> i) All RRF values must be greater than or equal to 0.05 <br /> ii) Percent difference (%D) values must not exceed 25 percent <br /> Calibration standards were analyzed at the required frequency, and the results met the above criteria for <br /> instrument sensitivity and stability. <br /> GC <br /> To ensure that the calibration of the instrument for organic analyses by GC is valid throughout the sample <br /> analysis period, continuing calibration standards are analyzed and evaluated on a regular basis. To evaluate <br /> the continued linearity of the calibration, %D values are calculated for each compound. As specified in the <br /> methods,all %D values should not exceed 15 percent. To ensure that compound retention times do not <br /> vary over the analysis period, all retention times for continuing calibration compounds must fall within the <br /> established retention time windows. <br /> All continuing calibration standards were analyzed at the required frequency. All %D values and compound <br /> retention times met the above criteria indicating acceptable instrument calibration throughout the analysis <br /> period. <br /> 6.0 Laboratory Blank Analyses <br /> Method blanks are prepared from a purified matrix and analyzed with investigative samples to determine <br /> the existence and magnitude of sample contamination introduced during the analytical procedures. <br /> For this study, laboratory method blanks were analyzed at a minimum frequency of 1 per 20 investigative <br /> samples and/or 1 per analytical batch. All method blank results were non-detect, indicating that laboratory <br /> contamination was not a factor for this investigation. <br /> EWAL EMRMM ENT GPW TUNJI EMPLMEF <br />