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CORE LABORATORIES <br />~~,~ <br />Western Atlas <br />International <br />.,,..,a... ~.., <br />r~ri <br />ANALYTICAL CHEMISTRY DIVISION QUALITY ASSURANCE MANUAL <br />' SOP N0. NEVISION ND. EFFECTIVE GATE PAGE <br />HC-QAC-02 0 1/06/92 73 of 104 <br />Split Samples <br />t Split samples are separate homogenous aliquots of a sample taken from the <br />same field site and submitted to two or more independent laboratories for <br />' analysis. <br />Split samples measure the reproducibility (accuracy) of analysis. <br />' Performance Evaluation Samples <br />' QC Check Samples <br /> QC check samples are samples which contain target analytes at known <br /> concentrations. This type of quality control check Sample is often <br /> submitted by clients and regulatory agencies a5 round robin or laboratory <br /> performance evaluation samples. Several QC check sample programs are <br />' used by Core Laboratories as a quality assessment measure of laboratory <br /> performance (see sections 15.6 and 15.7). <br />' If the analyst is not informed of the true target analyte concentration value, <br /> the sample is referred to as a "blind" QC check sample. <br />' If the analyst is not informed that the sample is a quality control check) <br /> sample, the sample is referred to as a "double blind" QC check sample. i <br />' At a minimum, QC check samples should be analyzed on a quarterly basis. II <br /> Blind Duplicates <br />I <br /> Blind duplicates are a measure of the repeatability within the laboratory. <br /> Blind duplicates are field samples which are split in the laboratory, logged <br />' in as two separate jobs and analyzed separately. Analysts are not <br /> informed of the identity of blind duplicate samples which 8re introduced. <br /> For homogenous samples, duplicate analyses should be within 20% RPD <br />' (relative percent difference). <br />' 13.2 Inorganic Requirements <br />~ General Quality Control Guidelines <br />' I <br />I <br />