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Attachment B <br />Explanation of QC Qualifier Codes <br />Qualifier Meaning <br />T8 (ESC) - Additional method/sample information: Sample(s) received past/too <br />close to holding time expiration. <br />Qualifier Report Information <br />ESC utilizes sample and result qualifiers as set forth by the EPA Contract Laboratory Program and <br />as required by most certifying bodies including NELAC. In addition to the EPA qualifiers adopted <br />by ESC, we have implemented ESC qualifiers to provide more information pertaining to our analytical <br />results. Each qualifier is designated in the qualifier explanation as either EPA or ESC. <br />Data qualifiers are intended to provide the ESC client with more detailed information concerning <br />the potential bias of reported data. Because of the wide range of constituents and variety of <br />matrices incorporated by most EPA methods, it is common for some compounds to fall outside of <br />established ranges. These exceptions are evaluated and all reported data is valid and useable <br />unless qualified as 'R' (Rejected). <br />Definitions <br />Accuracy - The relationship of the observed value of a known sample to the <br />true value of a known sample. Represented by percent recovery and <br />relevant to samples such as: control samples, matrix spike recoveries, <br />surrogate recoveries, etc. <br />Precision - The agreement between a set of samples or between duplicate samples. <br />Relates to how close together the results are and is represented by <br />Relative Percent Differrence. <br />Surrogate - Organic compounds that are similar in chemical composition, extraction, <br />and chromotography to analytes of interest. The surrogates are used to <br />determine the probable response of the group of analytes that are chem- <br />ically related to the surrogate compound. Surrogates are added to the <br />sample and carried through all stages of preparation and analyses. <br />TIC - Tentatively Identified Compound: Compounds detected in samples that are <br />not target compounds, internal standards, system monitoring compounds, <br />or surrogates. <br />Page 6 of 6 <br />