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Pace Analytical Services, Inc - New Orleans Laboratory Quality Control Definitions Our laboratory employs quality control (QC) measures to ensure the quality of our analytical ' data by defining its accuracy and precision Presentation of the QC data with the report allows the data user the opportunity to evaluate these results and to gauge the method performance In order to assist the understanding of these data, routine components of our QC program are defined below BATCH - A batch is a group of 20 samples or less of a given matrix and analysis by a specific protocol or analytical method BLANK - A method blank is a "clean" laboratory sample carried through the entire analytical process One or more method blanks are prepared with each batch of samples The analysis of method blanks demonstrates that method interferences caused by contaminants, reagents and glassware are known and minimized A method blank should not contain any analytes of interest above the reporting limit There are method allowances for common laboratory artifacts such as methylene chloride, acetone and bis-2-ethylhexyl phthalate LABORATORY CONTROL SPIKE - A laboratory control spike (LCS or blank spike) is a blank which has been spiked with known concentrations of target analytes The LCS is carried through the entire analytical process One or more LCS are prepared with each batch of samples The percent recovery of the spiked analytes provides a measure of the accuracy of the analytical process in the absence of matrix effects I MATRIX SPIKE - A matrix spike (MS) is a client sample which is spiked with known concentrations of target analytes The MS is carried through the entire analytical process One or more matrix spikes are prepared with every batch of samples For organic methods, a matrix spike duplicate (MSD) is also prepared The percent recovery of the spiked analytes provides a measure of the method accuracy in the selected sample and matrix DUPLICATE - A duplicate is a sample for which replicate aliquouts are tamed through the entire analytical process Comparison of the original results to those of the duplicate results provides a measure of the method precision in the sample and matrix By convention, precision is measured for inorganic analyses using a sample and a sample duplicate, whereas for organics analyses, an MS/MSD are used SURROGATE - A surrogate is a non-target analyte which is added to all samples and QC samples prior to extraction or analysis The percent recovery of the surrogate provides a measure of the method accuracy in each sample tested Surrogates are used for organics methods only QC LIMITS - QC limits specify the expected percent recovery range for a spiked compound QC limits may be set by method criteria or calculated from laboratory generated data For many methods, these limits are advisory and do not require corrective action if exceeded