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1 <br /> ' section 10 <br /> ONSITE Environmental Laboratories, Inc Revision 0 <br /> Quality Assurance Pian February 13, 1996 <br /> Page 3 of 6 <br /> The equation for calculating RPD is given in Section 7 2 1 <br /> 10 1 S Matrix Spikes <br /> ' Samples representative of the matrix being analyzed are spiked with known <br /> amounts of the analytes These are used to assess the accuracy of the analysts <br /> by measuring the recovery of parameters of Interest, and to identify or rule out <br /> ' any chemical interferences from the sample matrix All analytical, extraction, <br /> and digestion batches for tests which are not quantitative or which are not <br /> feasible to spike (such as odor, turbidity, or alkalinity) are required to be split <br /> and analyzed at a frequency of at least 5% <br /> In this process, a sample is analyzed routinely and a second aliquot has a <br /> ' known amount of the analytes added before it is taken through the entire <br /> preparation and analysis process Spiked samples are performed on one sample <br /> in each batch of ten or twenty samples, depending upon the method <br /> requirements, and/or each type of sample matrix The amount of spike added <br /> varies depending on the working range of the analytical instrument but is <br /> always no less than 10times (10x) the MDL but no more than 10 times (10x) <br /> the RL and is listed in each individual method SOP <br /> The value of both the unspiked andspiked aliquots is deterrruned The percent <br /> ' (%} recovery of the spike is calculated using the equation in Section 7 2 2 2 <br /> Should the unspiked aliquot have a detectable amount of the analyte, that value <br /> is subtracted from rhe observed value of the spike in the calculation <br /> ' At times it is impossible to know the magnitude of the analyte before the spike <br /> is added and the value of the unspiked sample is outside of the operating range <br /> of the instrument The sample and the spiked aliquot may require dilution to <br /> bring the analysts within the dynamic range of the instrument This dilution <br /> will adjust the analyte in the sample to a usable concentration but may dilute <br /> the spike to an unusable level The analyst in this case will not be able to <br /> ' report spike recovery for that particular analyte <br /> If the sample used for spike recovery data has been diluted to unusable levels <br /> ' or is out of criteria for some other reason, the final report will be <br /> supplemented by the analysis of spiked blank samples and other QC sample <br /> data <br /> 10 1 6 Blank Spikes <br /> Since matrix spike samples occasionally will demonstrate an interference, blank <br /> samples are spiked and used as a second check on the accuracy of both the <br /> Word 6 0 loeisec10 doc <br /> 1 <br />