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n <br />h - <br />U <br />0 <br />n <br />n <br />C <br />n <br />Project Plan <br />Revision 6 <br />1/8/1988 <br />Page 15 of 37 <br />one matrix spike (known amount of analyte spike on sample) should be <br />run for every 10 samples to monitor the interference of the sample matrix <br />to the analysis. This information will help the chemist to be familiar with <br />different types of matrices and to make proper modification of sample <br />extraction for future analysis. The analyte used in the matrix spike may <br />be from a different source than the check sample. <br />Spike recovery (P) will be calculated as follows: <br />P = 100 x (A-B)/T <br />where: A = measured concentration of contamination after spiking. <br />B = Background concentration of contaminant. <br />T = Known value of the spike. <br />5.1.3.4 Matrix S ike Duplicate/Duplicate <br />One duplicate should be run for every 10 samples in order to assure <br />the reproducibility of the analysis for a specific sample type. If the % <br />R.S.D. (Relative Standard Deviation) is outside the Laboratory Control <br />Limit, the problem should be identified and with solution documented in <br />note book before repeating the analysis. <br />R.S.D. = <br />5.1.3.5 Surrogate Spike <br />Addition of surrogate spike as called for in the method in each check <br />sample, standard sample, and blank for volatile and semi -volatile organic <br />analysis prior to extraction serves to monitor both the instrument and <br />extraction. <br />Surrogates are organic compounds which are similar to analytes of <br />interest in chemical composition, extraction and chromatography, but which <br />21 <br />