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EI eco <br /> T C.-C COMPAnv <br /> [a:l <br /> Single Control Sam le. An SCS consists of a control matrix that <br /> . is spiked with surrogate compounds appropriate to the method being <br /> used. In cases whera no surrogate is available, (e.g. metals or <br /> conventional analyses) a single control sample identical tc the <br /> DCS serves as the control sample. An SCS is prepared for each <br /> sample lot. Accuracy is calculated identically to the US. The <br /> ! SCS results associated with Your samples are on the attached <br /> J ! Single Control Sample Report. <br /> Accuracy is measured by Percent Recovery as in: <br /> % recovery = measured concentration x 100 <br /> (actual concentration) <br /> Fy <br /> .,s Precision is measured using duplicate tests by Relative Percent Difference <br /> (RPD) as in: <br /> RPD = f90 recovery test_1 - % recovery test 21 x 100 <br /> (% recovery test I + % recovery test 2)/2 <br /> Control limits for accuracy (percent recovery) are based on the average, <br /> historical percent recovery +/-3 standard deviation units. Control limits <br /> for precision (relative percent difference) range from 0 (identical <br /> rR; duplicate DCS results) to the average, historical relative percent <br /> difference + 3 standard deviation units. In cases where there is not <br /> enough historical data, EPA limits or advisory limits are set, with the <br /> approval of the Quality Assurance department. <br /> !A IV Analysis Results <br /> Test methods may include minor modifications of published EPA Methods such <br /> !1 '4 as reporting limits or parameter lists. Reporting limits are adjusted to <br /> reflect dilution of the sample, when appropriate. Solid and waste samples <br /> +y are reported on an "as received" basis, i.e., no correction is made for <br /> moisture content, unless the method requires or the client requests that <br /> such correction be made. <br /> Results are on the attached data sheets. <br /> N 3 , <br /> 4`•t <br /> sF . <br /> �ws <br /> 1_5 <br />