Sample Batch Preparation and Extraction

The apparently mundane task of collecting together the analytical samples to be analyzed in a sample batch run, together with the appropriate blanks, calibrators and QCs, is a crucial component of a successful analysis. A batch list that describes of all the components needed for an analytical run should be prepared prior to the initiation of any work. In addition, a list of all samples that will be analyzed in the run, a description of all standards, QCs and blanks that need to be prepared is often included as part of the batch list. Depending on the apphcation, the types and number of blanks (extracted and/or solvent) that wiU be nsed may vary but in many instances at least one matrix blank with no internal standard (double blank) and one blank with internal standard should be included. The control matrix that is used for preparation of the extracted blanks shonld be screened prior to use (Section 9.4.7), to ensure that no appreciable interfering peaks that would impede the abdity to meet acceptance criteria elute at the retention time(s) of the analyte(s) of interest. 

For bioanalytical analyses, it is recommended that the number of QC samples in a run must be at least 5 % of 

In cases where stndy sample concentrations are likely to differ significantly from the established analytical QC concentrations specified in an SOP, or by client directive, additional QC samples may be prepared and analyzed to ensure that the QC samples are representative of the sample concentrations anticipated in the study. The concentrations of these additional QCs should be determined through agreement with the client and should be fuUy documented with all supporting raw data. These additional QC samples are to be analyzed as a number of replicates that should be specified in the appropriate SOP. Acceptance criteria for the additional QCs should follow the criteria used for the other analytical QCs in the batch. 

It is equally important that the sample preparation (extraction and clean-up) of the batch must be done carefully in accordance with the procedmes established by the validated method and any prevailing SOPs. The analysts conducting these tasks must be trained on the applicable SOPs and this training must be documented in their training records. Study samples must be analyzed within known analyte stabihty constraints for the matrix and the processed extracts. When sufficient stability has not been established at the time of sample reporting (e.g. long term freezer stability may be on-going at the time of analysis), this must be clearly documented within the study report. 

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