Innovative Configurations of Sample Preparation Techniques Applied in Bioanalytical Chemistry: A Review

Background: Recently, in all fields of analytical chemistry, increased attention has been paid to extraction procedures and instrumental methods, which are easily scalable and are able to automate in order to improve the “high-throughput” capability. Introduction: The main goal of these applications relates to an improvement of the precision in the quantitative analysis, reduction of different sources of errors, decrease the analysis time and, in general, improve the analytical performances. Often these points can be in contrast to each other, not allowing to achieve the expected result but forcing a compromise between the objectives of the method and the analytical performance. Method: In this review, following the evolution of the (micro)extraction procedures and instrument configurations, the recent procedures used in bioanalytical chemistry are critically evaluated. The aim of this paper is providing an overview of the approaches available in order to perform on-line coupling of various extraction techniques with chromatographic methods for the analysis of different compounds in various samples. Furthermore, a comparison between off-line and on-line systems, advantages of on-line systems applied on major extractive techniques and future perspectives are described. Result: The extraction methods suitable for on-line coupling covered in this review are: liquid-liquid extraction (LLE), solid phase extraction (SPE), solid phase microextraction (SPME), dispersive liquid-liquid microextraction (DLLME), microextraction by packed sorbent (MEPS), supercritical fluid extraction (SFE) and fabric phase sorptive extraction (FPSE). Conclusion: An overview of the micro-extraction techniques mentioned above was provided, making a comparison between them and focusing attention on future perspectives.