Basic Sample Preparation Techniques in LC‐MS Bioanalysis

In order to ensure adequate sensitivity, selectivity and reproducibility of the LC-MS/MS assay method for measuring analyte(s) of interest in biological samples, sample preparation, also known as sample pretreatment or sample cleanup, is a must step. Sample preparation in LC-MS bioanalysis is a pre-analytical separation process that involves selective isolation of analyte(s) of interest from the matrix, minimization or elimination of matrix components in the extracted samples and, if necessary, enrichment of analyte(s). Due to the many factors affecting matrix removal and analyte recovery, developing an optimal sample preparation procedure can be very difficult, tedious and labor-intensive, which makes it one of the most significant parts in the development of a LC-MS bioanalytical method development. In this chapter, we are describing the commonly used sample preparation techniques in LC-MS bioanalysis, namely protein precipitation (PPT), liquid-liquid extraction (LLE) and solid phase extraction (SPE), with an introduction of physicochemical properties that will determine extractability of the analyte(s) and with a focus on the need for balancing extraction recovery and assay selectivity. The mechanism, major components, advantages and disadvantages of each technique are discussed in detail along with example protocols to demonstrate the procedure.