Chapter 23 Sampling and sample preparation for clinical and pharmaceutical analysis

Abstract

Drug analysis in biological samples and pharmaceutical products is very important for therapeutic drug monitoring (TDM), pharmacokinetic studies, and screening of illicit drugs and development of new medicines. Various biological specimens, particularly plasma, serum, and urine have been used as samples for analysis. The use of milk, tissues, faces, and breath samples for drug analysis are unusual in clinical applications. Pharmaceutical products provide various formulation types such as solids, liquids, topicals, injectables and inhalants, and various excipient actions for tablets, capsules, coatings, flavorings, colorings, buffers, suspending, and preservatives. Clean up of these samples for the analysis of target drugs are commonly performed by liquid-liquid extraction (LLE), solid-phase extraction (SPE), solid-phase microextraction (SPME) and their combination after precipitation, centrifugation and dialysis. Supercritical fluid extraction (SFE), SPE, SPME, immunoaffinity extraction (IAE), liquid-phase microextraction (LPME), and microwave-assisted extraction (MAE) have been developed as newer sample preparation techniques. Among these techniques, SPE is the most popular sample preparation technique for drug analysis. SPME is becoming an attractive alternative to SPE and LLE for some applications. SPME is a solvent-free and concentrating extraction technique and applied for the analysis of drugs and metabolites in biological fluids. The most striking attribute of SPME is its low total recovery as reported for many methods.