On-line desalting of physiologically derived fluids in conjunction with capillary isoelectric focusing-mass spectrometry

Capillary isoelectric focusing (cIEF) coupled to mass spectrometry (cIEF-MS) offers a potentially very powerful analytical tool for the investigation of physiological samples. The high resolving capabilities of cIEF in combination with the high sensitivity and enhanced structural information provided by MS is highly desirable for the analysis of complex samples. However a major limitation of the technique has always been the requirement to desalt samples prior to cIEF analysis. Such desalting normally occurs off-line and therefore adds complexity and the possibility of sample loss or contamination. In this study we demonstrate the use of a modified cIEF protocol which enables samples containing physiological levels of salts to be desalted on-line, within the cIEF capillary. This new technique is very fast and efficient, allowing the direct analysis of a physiologically derived fluid that contains a complex mix of proteins, such as human cerebrospinal fluid by cIEF-MS in a single step experiment. (C) 1997 American Society for Mass Spectrometry.