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LFR Levine-Fricke <br /> (Cl -C2) <br /> RPD = x 100 <br /> (Cl + C2)/2 <br /> Where: <br /> RPD:relative percent difference <br /> Cl:larger of the two observed values <br /> C2: smaller of the two observed values <br /> Imprecision in MS/MSD results is usually an indication of sample matrix effects <br /> whereas imprecision of field duplicate (collocated) sample results may be an indication <br /> of sample heterogeneity or multiplicative interferences that diminish or enhance <br /> analytical signals. Sample results that do not meet precision objectives may still be <br /> considered usable for Data Quality Objectives based upon professional judgment as to <br /> the cause and magnitude of the imprecision. All such decisions will be clearly justified <br /> in the data usability section of the validation report. <br /> G1.4.3 Sensitivity- Detection Limits <br /> The method detection limit(MDL)is the minimum concentration of an analyte that can <br /> be identified using a specific method. The laboratory usually determines the MDL by <br /> calculating the standard deviation of the results of seven replicate spike sample analyses <br /> and multiplying by three,using reagent water as a sample. The MDL is an ideal <br /> detection limit when there is no background laboratory contamination and the sample to <br /> be analyzed is a clean sample free of matrix effects. MDLs, also known as the method <br /> quantitation limit, are determined using reagent water as the sample. MDLs are not <br /> field sample specific and do not vary with the sample preparation or dilutions required <br /> for each field sample analyzed. The MDL is the instrument detection limit(IDL)plus <br /> adjustments for typical sample preparation techniques. <br /> Sensitivity for this project will be evaluated against the specific project MDLs and <br /> internal standard recoveries. Quantitation limits may be affected by matrix interferences. <br /> If a dilution is required, the lowest dilution necessary to bring the compound within <br /> range should be performed in all cases. In cases where the specified detection limits(or <br /> project-specific reporting limits)are not achieved, the usability of the data will be <br /> evaluated by LFR. <br /> G1.4.4 Representativeness <br /> Representativeness expresses the degree to which the sample data accurately and <br /> precisely represent the media being sampled at a specific location at a specific time. <br /> One measure of representativeness is field duplicate precision. If field duplicate <br /> precision criteria are not met, LFR will determine usability of the associated results <br /> and qualify the data based upon best professional judgment. Poor field duplicate <br /> precision may be an indication of sample heterogeneity or poor sampling. <br /> Page G-6 Final_RAP_Tracy_9.18.03(final).doaLFR <br />