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Page II of 24 <br />SOP NUMBER 28.0 Analytical Data Validation <br />4.1.7.4 Trip Blank Results <br />The results for trip blanks reported in the data package will be reviewed. Sample results for <br />analytes detected in an associated trip blank at concentrations <5x the equivalent blank <br />concentration (<I Ox for common laboratory contaminants) will be qualified as nondetect ("U"). <br />The result will be qualified as nondetect at the reported concentration if the reported <br />concentration is >RL or as nondetect at the RL if the reported concentration is <RL. <br />For aqueous blanks applied to soil/sediment samples, qualification is assigned based on <br />comparison of the sample result to the equivalent concentration in the blank. The equivalent <br />concentration is determined by assuming that all of the analyte present in the blank aliquot <br />analyzed is present in the soil sample aliquot analyzed. The reviewer should note that the blank <br />analyses may not involve the same weights, volumes, or dilution factors as the associated <br />samples. These factors must be taken into consideration when applying the 5x or l Ox criterion, <br />such that a comparison of the total contamination is actually made. <br />A qualifier code of "TB" will be assigned to all results qualified on the basis of rinsate blank <br />results. A bias code of indeterminate will be assigned. <br />4.1.8 Reporting Limits <br />For the contracted laboratories are reporting positive results below their standard reporting limits <br />(RLs) when the values are greater than the instrument detection limit (IDL) or method detection <br />limit (MDL). These detection and/or reporting levels and associated degree of uncertainty are <br />discussed below. <br />The MDL is defined in 40CFR136, Appendix B as the minimum concentration of a substance that <br />can be measured and reported with 99% confidence that the analyte concentration is greater than <br />zero. The MDL is determined from the analysis of spiked samples containing the analyte in a given <br />matrix. MDLs are preparation- and method-specific. The MDL is calculated by multiplying the <br />standard deviation of the measurements by the student t-value for seven replicate analyses (i.e., <br />3.14). <br />Inorganic results are reported down to the instrument detection limit (IDL). An IDL determined by <br />analyzing seven replicates of an undigested, spiked, clean sample matrix on 3 non-consecutive days. <br />For each day, the standard deviation of the readings is calculated. The standard deviations are then <br />averaged and multiplied by 3. Thus, the IDL represents the concentration level necessary to <br />produce a signal greater than 3 times the average standard deviations of the mean noise level for the <br />21 sample analyses. <br />At the MDL or IDL, results may have a high degree of uncertainty in the actual concentration (often <br />more than 100%). Results reported as detected at the IDL may also have about a 50% chance of <br />being nondetects (i.e. false positives meaning that the true sample concentrations are less than the <br />IDL or MDL). <br />RLs or Practical Quantitation Limits (PQLs) are typically set at some factor above the IDL or MDL <br />to ensure greater confidence in the accuracy of the associated quantitative value. Thus, at the RL (or <br />PQL), a value typically set at 3-10 times the IDL or MDL, the degree of uncertainty would be more <br />like +/- 25%. Thus, the PQL is the smallest concentration of the analyte that can be reported with a <br />specific degree of confidence (i.e., the low concentration point of the calibration curve is less than or <br />Powertech <br />Rev 28-1 JAB Attachment A <br />4/23/2007 <br />R Squared Inc <br />Is,