Sorptive microextraction for liquid-chromatographic determination of drugs in urine

Biological fluids are common samples in clinical and toxicological laboratories, urine being used most due to its availability. However, its inherent complexity, with the presence of many substances and the low concentration of target analytes, means that, in most cases, its direct analysis is not feasible. Sample pre-treatment, focusing mainly on enhancement of selectivity and sensitivity, is usually unavoidable prior to quantification.In this review, we focus on the sorptive microextraction of urine samples prior to the determination of analytes of interest by liquid chromatography. We comment on the most important developments, namely:
• fiber and in-tube solid-phase microextraction;
• stir-bar sorptive extraction; and,
• microextraction in packed syringe.We describe the most relevant examples reported in the literature to show clearly how useful this technique is for the determination of endogenous and exogenous compounds in urine samples.