Coupling microextraction techniques with substrate spray mass spectrometry, towards a faster analysis of biological samples

Direct coupling sample preparation with mass spectrometry has risen as a reliable analytical strategy in bioanalysis as it provides a high sample throughput. This approach avoids an exhaustive separation step, thus being cost-effective compared to the traditional analytical workflow. The selectivity and sensitivity levels rely on the mass spectrometric analysis and the appropriate selection of the sample preparation. Miniaturized extraction techniques have demonstrated particular utility in this coupling thanks to their ability to pre-concentrate the target analytes while removing many of the matrix components. This article reviews the main developments in combining microextraction techniques with mass spectrometry based on electrospray ionization, a consolidated ionization technique in bioanalysis. The article aims to provide an overview of the potential of these techniques by describing the most significant examples. The different approaches are classified according to the materials or devices used to perform the extraction and analysis.