What is the purpose of analyzing the matrix spike (MS) sample versus analyzing the laboratory control sample (LCS) and why should we run both?
The MS/MSD results are an important measure of the performance of the method relative to the specific sample matrix 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 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 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.
Therefore, the LCS results should be used in conjunction with MS/MSD results to separate issues of laboratory performance and "matrix effects."
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. 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.