Sample Preparation Techniques for Mass Spectrometry in Proteomics Using Recently Developed Highly Selective Materials

Efficient sample preparation in the micro and nano-litre range, prior to analysis of proteins and peptides of biological origin by liquid chromatography (LC), liquid chromatography coupled to mass spectrometry (LC-MS), micro- liquid chromatography (μ-LC) and matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry, is the key to success for different applications, such as biomarker discovery. Sample preparation in proteomics mainly comprises purification and preconcentration by solid-phase extraction (SPE) using different polymers (polystyrene, poly acrylate, cellulose, etc.) as a stationary phase following several cleaning-up procedures. These polymers can be derivatized with several functional groups, for example, C18, ion-exchanger or immobilized metal affinity chromatography (IMAC) groups. Based on these "traditional" techniques new methods enabling higher selectivity, sensitivity and speed of separation are required. Capillary coatings, for example, with latex particles has been used successfully. Derivatization of these latex particles, for example, with IMAC-functional groups enables a selective purification of phosphorylated or His-tagged proteins. Alternatively, polymeric disks possessing a thickness of approximately 2 mm can be used even in the case of multidimensional separations. In this review, we summarize currently available sample pretreatment techniques, provide an overview on the technical background and discuss the advantages of the individual methods using recently developed selective stationary phases such as silica based materials, polymers, etc.