398. reactive metabolite Drugs are generally converted to biologically inactive forms and eliminated from the body, principally by hepatic metabolism. However, certain drugs undergo biotransformation to reactive metabolites that can interfere with cellular functions. These are often electrophilic and can interact with DNA and proteins to form covalently bound products.
399. reanalysis Repetition of a series of analytical procedures, from the processing step on, on samples that have been previously analyzed.
400. recovery (extraction) The extraction efficiency of an analytical process, reported as a percentage of the known amount of an analyte carried through the sample extraction and processing steps of the method.
401. reference standard A well-characterized substance used to spike calibration standards and QC samples in a method, accompanied by a certificate of analysis (CoA) that provides the purity and expiration (or retest) date.
