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10.3.2 MATRIX SPIKE/MATRIX SPIKE DUPLICATE (MS/MSD/DUPLICATE <br /> ANALYSES <br /> For inorganic analyses, MS/MSD or MS/Dup samples will be analyzed at a minimum <br /> frequency of one per ten investigative samples. For organic analyses, MS/MSD or <br /> MS/Dup samples will be analyzed at one per twenty investigative samples or one per <br /> extraction set, whichever is more frequent. Representative analytes of interest will be <br /> used as spiking compounds. Percent spike recoveries will be used to evaluate analytical <br /> accuracy while RPD values will be used to assess analytical precision. Control limits <br /> will be established by the laboratory. <br /> 10.3.3 SURROGATE ANALYSES- ORGANICS <br /> Surrogates are organic compounds which are similar to the analytes of interest, but <br /> which are not normally found in environmental samples. Surrogates are added to <br /> samples to monitor the effect of the matrix on the accuracy of the analysis. Every blank, <br /> standard, and environmental sample analyzed will be spiked with surrogate <br /> compounds prior to sample extraction and/or analysis. <br /> The compounds that will be used as surrogates and the recommended spiking levels are <br /> suggested in the analytical method. The laboratory will select surrogates based on the <br /> method control limits. If surrogate recoveries are excessively low (<10 percent), the <br /> laboratory will contact CRA for further instructions. <br /> Dilution of samples to bring the analyte concentration into the linear range of calibration <br /> may dilute the surrogates out; reanalysis of these samples is not required. Assessment <br /> of analytical quality in these cases will be based on the MS/MSD sample analysis <br /> results. <br /> 031090-10(4) -17- CONESTOGA-ROVERS&ASSOCIATES <br />