Laboratory Quality Control Samples. Laboratories routinely perform medium spike and laboratory duplicate analysis on field samples as a quality control check. A minimum of one field sample per week or 1 per 20 samples (including field blanks and duplicates), whichever is greater, must be designated as the "Lab QC Sample" for the medium and laboratory duplicate analysis. Laboratory quality control samples should be selected from sampling points which are suspected to be moderately contaminated. Label the bottles and all copies of the paperwork as "Lab QC Sample"; the laboratory must know that this sample is for their QC analyses. The first laboratory QC sample of the sampling effort should be part of the first or second day's shipment. Subsequent laboratory QC samples should be spread out over the entire sampling effort. For water media, 2-3 times the normal sample volume must be collected for the laboratory QC sample. Additional volume is usually not necessary for soil samples.
Laboratory Quality Control Samples. For each batch of samples, additional samples are prepared at the laboratory. These samples include: method blanks, low concentration or control check standards, laboratory check standards, matrix spike and matrix spike duplicate (MS/MSD) results. Blank or low concentration spike samples and duplicates are prepared to determine if any contamination has occurred in the laboratory and to determine the percent recovery at low concentrations. Preservative blanks are also prepared in the laboratory to determine if any contamination was introduced from the preservatives. The MS/MSD samples are used to determine percent recoveries of the reference standards and matrix spikes, and are used to detect matrix interferences. The laboratory duplicate samples are used to determine the relative percent differences, which can be used to detect laboratory equipment problems such as drift in calibration. The frequency of these QA/QC samples and actions that can be taken are shown in Table 5 for mercury and in Table 6 for the other chemical ancillary parameters. A quality assurance/quality control (QA/QC) summary form will be completed by the laboratory for water and sediment samples. The sample numbers for all QA/QC rinseate samples, reference samples, laboratory QC samples, and duplicates will be documented on this form so that the QA/QC samples can be associated with each batch of environmental samples. QA Sample QA Measure Quality Control Criteria for Analysis of Mercury Minimum Frequency Acceptance Limits Corrective Action* Total and Dissolved Iron Method Blank Limit Study Method Blank Spiked at PQL Determine MDL Determine PQL Run 20 Method Blanks per batch of samples Run 20 spiked samples per batch of samples MDL is 3X standard NA deviation of mean of 20 blanks PQL is 4 X MDL or mean NA of spiked blanks Method Blanks Analyzed with Samples Accuracy 3 per analytical batch, whichever contains fewer samples Analyte >MDL Check reagents, clean instrument, prepare fresh standards and reanalyze samples Certified Reference Material (CRM) Accuracy Once per analytical batch Analyte Specific 75%< CRM<125% THg; 70%< CRM <130% MeHg Check reagents and clean instrument, and reanalyze samples. Accepting the data and acknowledging the level of uncertainty with a written explanation Replicate Precision Once every 10 samples or every analytical batch, whichever contains fewer samples Analyte Specific 75%< %D <125% THg; 70%< %D <130% MeHg Reanalysis of samples Accepting the data and acknow...
Laboratory Quality Control Samples. A minimum of one field sample per week or 1 per 20 samples (including field blanks and duplicates), whichever is greater, must be designated as the "Lab QC Sample" for the matrix and laboratory duplicate analysis. Laboratory quality control samples should be selected from sampling points which are suspected to be moderately contaminated. Label the bottles and all copies of the paperwork as "Lab QC Sample"; the laboratory must know that this sample is for their QC analyses. The first laboratory QC sample of the sampling effort should be part of the first or second day's shipment. Subsequent laboratory QC samples should be spread out over the entire sampling effort. For water matrices, 2-3 times the normal sample volume must be collected for the laboratory QC sample.
