Direct derivatization of drugs in untreated biological samples for gas chromatographic analysis

The possibilities to derivatize an analyte directly in the biological sample are reviewed with examples from our own experiences and from the literature. Techniques, such as extractive acylation, alkylation and benzoylation, are frequently used. Improvement of the extractability of the drug from the matrix is a common feature, especially with hydrophilic compounds, where sometimes cyclizing reactions can be employed. Several analytes are reactive or labile in the sample and can be trapped in derivatization reactions in situ. In many cases, two-phase reactions lead to milder derivatization conditions (e.g. dealkylation of tertiary amines), which is favourable from a clean-up point of view.