Laboratory Reference Samples
Purchased or prepared samples that have been certified by a recognized agency to contain specified levels of selected constituents, when measured by specified standard procedures. Results are expressed as a percentage of the design value.
Frequency and Purpose
During validation mandatory, otherwise optional.
Used for validating the performance of a method including precision, extraction or digestion efficiency. Preferably these are Certified Reference Materials (CRM); if these are not practical, spikes or surrogates may be used instead.
Application and Regulatory Criteria
Applicable for all analytical parameters where CRMs are commercially available. Acceptable recovery ranges are provided by the supplier. Ideally, should be within 85-115% of the long-term mean / design value / certified target value. Recommended to use control charts, especially for organic contaminants; values should ultimately be no more than ±3 standard deviations of the mean / design / target value.
Repeat the analysis for all samples in the batch, if CRM % recovery is outside control limits.