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CALIFORNIA WATER LAS <br /> QUALITY ASSURANCEJGUALfTY CONTROL <br /> MANAGEMENT SUMMARY <br /> (Continued) <br /> Matrix Spikes <br /> To assess accuracy. a sample is chosen at random to spike with an analyte of <br /> interest. Matrix spikes must be analyzed for every 20 samples or similar matrix or per <br /> batch, whichever is more frequent. Spiked samples are reviewed in terms of percent <br /> recovery. <br /> Spike Duplicates <br /> To assess precision, the matrix spike above is prepared and analyzed in duplicate- <br /> This is done because many samples will not contain the analyte of interest and may <br /> not provide precision data. Spike duplicates are analyzed at the same frequency as <br /> matrix spikes, and results are compared in terms of the relative percent difference <br /> - (RPD) between the percent recovered for each of the duplicates. <br /> Acceptance criteria are as follows: <br /> inorganic. Warning limits for RPD and%Recovery are defined as±2X the standard <br /> deviation of the mean. Out-of-control limits for RPD and % Recovery are defined as <br /> + 3X the standard deviation of the mean. <br /> Organic. Out-of-control limits for RPD and % Recovery are defined as + 2X the <br /> standard deviation of the mean with some exceptions that are ± 3X the standard <br /> deviation, <br /> Note: These limits do not apply to leachate e_+dracdons. <br /> Instrument Colibrotions <br /> All analytical instruments are calibrated using standards of at least three different <br /> - concentrations, including a standard at the concentration of the lirnit of detection. <br /> Samples must be diluted so that the raw data fall within the concentration of the <br /> calibration. Acceptable methods for linearity include correlation coeMcient, %RSD, <br /> and least squares curve fitting. <br /> CWL uses the protocol outlined in USEPA Contract Laboratory Program, State- <br /> ment of Work for Organic Analysis Multi-Media, Multi-Concentration, 10/86 <br /> revision, for tuning and calibration of all GC/MS systems. <br /> Method Spikes <br /> When samples are extracted or digested,a method blank is spiked with an analyte <br /> of interest. The analysis of this sample may provide information regarding the <br /> preparation efficiency when matrix interferences are present_ <br /> 5 <br />