![]() The Office of Resource Conservation and Recovery (ORCR) also recognizes that other frequencies may be appropriate under certain circumstances. The 1 per 20 (5%) frequency is a typical value that has been used in many EPA programs for many years. Why do so many of the QC operations (MS, MSD, LCS, blanks, etc.) have to be run "once for every 20 samples?" Why do many of the SW-846 quality control (QC) operations have to be run "once for every 20 samples?" Appropriate use of a single set of MS/MSD results is to evaluate method performance in the matrix of interest, not to evaluate laboratory performance. ORCR believes that consistent trends in MS/MSD results can be of some use in evaluating laboratory performance, as are trends in surrogate recoveries, LCS recoveries, and other QC data. Therefore, the LCS results should be used in conjunction with MS/MSD results to separate issues of laboratory performance and "matrix effects." The primary purpose of the laboratory control sample (LCS) is to demonstrate that the laboratory can perform the overall analytical approach in a matrix free of interferences (e.g., in reagent water, clean sand, or another suitable reference matrix) and its analytical system is in control. The primary purpose of these MS/MSD analyses is to establish the applicability of the overall analytical approach (e.g., preparative, cleanup, and determinative methods) to the specific sample matrix from the site of interest. The Office of Resource Conservation and Recovery (ORCR) believes that such a demonstration is an important aspect of an overall quality assurance program, and is particularly important for the RCRA program, which governs a wide range of different matrices. The MS/MSD results are an important measure of the performance of the method relative to the specific sample matrix of interest. What is the purpose of analyzing the matrix spike (MS) sample versus analyzing the laboratory control sample (LCS) and why should we run both? Are Method Detection Limit (MDL) studies required for SW-846 test methods?.Differences in quality control (QC), preservation, and holding time recommendations among SW-846 parts.For SW-846 Methods 13, is it an acceptable alternative to use internal standards for all leachates?.Spiking surrogates for SW-846 Methods 3510C and 3520C.Can you clarify the quality control (QC) requirements for SW-846 Method 9060A, Total Organic Carbon (TOC)?.What is the SW-846 position concerning the use of accuracy measurements determined from the matrix spike in place of the laboratory control sample?.For SW-846 Method 5030 combined with Method 8260, is the Tune Batch equal to the Analytical Batch?.What is the procedure when matrix interference effects cause elevated TCLP Lower Limit of Quantitation (LLOQ) that are above the TCLP regulatory limits?.Why do many of the SW-846 quality control (QC) operations have to be run "once for every 20 samples?".What is the purpose of analyzing the matrix spike (MS) sample versus analyzing the laboratory control sample (LCS) and why should we run both?.
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