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BATCH QC REPORT: Definitions and Terms Accuracy The ability of a procedure to determine the "true" concentration of an analyte Precision The reproducibility of a procedure demonstrated by the agreement between analyses performed on either duplicates of the same sample or a pair of duplicate spikes Batch A group of samples analyzed sequentially using the same calibration curve, reagents, and instrument Laboratory Laboratory reagent water spiked with known compounds and subjected to the Control Standard same procedures as the samples The LCS thus indicates the accuracy of the (LCS) analytical method and, because it is prepared from a different source than the standard used to calibrate the instrument, it also serves to double-check the cahbratlon Matrix QC Quality control tests performed on actual client samples For most inorganic analyses, the laboratory uses a pair of duplicate samples and a spiked sample For most organic analyses, the laboratory uses a pair of spiked samples (duplicate spikes) LC Result Laboratory result of an LCS analysis LT Result Expected result, or true value, of the LCS analysts R1, R2 Result Result of the analysts of replicate aliquots of a sample, with R1 indicating the first analysts of the sample and R2 its corresponding duplicate, used to determine precision S 1, S2 Result Result of the analysis of replicate spiked aliquots, with S 1 i ndicauang one spike of the sample and S2 the second spike, used to determine precision and accuracy R Bar Result The average of replicate analysis results S Bar Result The average of spike analysis results True value The theoretical, or expected, result of a spike sample analysts Percent The percentage of analyte recovered Recovery For LCS, the percent recovery calculation is LC- LT x 100 For spike recoveries, the percent recovery calculanion is (S Bar- Sample Concentration) X100 Spike Amount Relative Percent Calculated using one of the following Difference (RPD) (R1_- R2) x 100 (S 1 - S2) x 100 (R1 + R2) - 2 (S1 } S2) - 2 . Blank Result The result of the analysis of a method blank,which is reagent water that is analysed using the same reagents, instruments and procedures as the samples in a batch, used to determine laboratory contamination Reporting Detec- BCA-assigned limit based on—but not the same as—method detection limits tion Limit (RDL) (MDLs) determined using EPA guidelines 13 L 4nalvitcul