SODIUM DODECYL-SULFATE REMOVAL FROM TRYPTIC DIGEST SAMPLES FOR ONLINECAPILLARY LIQUID-CHROMATOGRAPHY ELECTROSPRAY MASS-SPECTROMETRY

An on-line microcolumn switching method was developed for the removal of sodium dodecyl sulphate (SDS) from tryptic digest samples. The syst em includes two micro-precolumns: a specific ionic detergent trapping column and a preconcentration column. Characterization of the proteina ceous samples, after isolation from the SDS, was performed by capillar y liquid chromatography (LC) with UV absorption detection and electros pay mass spectrometry (ESI-MS). Loading and clean-up of the samples an d regeneration of the detergent trapping column were performed at 50 m u l min(-1), resulting in sample clean-up times of only 30 s. SDS-cont aining tryptic digested protein samples were directly applied to the m icro-precolumns without any previous sample pretreatment. The develope d microcolumn switching method permits the on-line analysis of small t ryptic digest samples by capillary LC/ESI-MS in the presence of SDS. T he method is completely automated and can be performed unattended. The maximum amount of SDS, in terms of loadability and breakthrough, were determined. Also studied were the selection of the loading and clean- up solvents and the recovery of the peptides. Chromatographic separati ons and mass spectral data confirmed the removal of SDS.