Under normal circumstances, cerebrospinal fluid (CSF) is a clear and colorless fluid that is formed in the ventricles of the brain. It is in close proximity to the surface of both the brain and spinal cord, and, as a result, the analysis of CSF proteins and other constituents in samples taken by lumbar puncture have long been used as an aid in the diagnosis of neurological disorders. Various electrophoretic methods have been used, including agar gel (1 ), polyacrylamide (2 ), two-dimensional (3 ), and isoelectric focusing (4 ), with the aim of detecting profiles that are diagnostic, especially in the case of proteins. These techniques have been labor-intensive, time-consuming, and, at best, only semiquantitative. This chapter describes how the technique of capillary electrophoresis (CE) in free solution (FSCE) can be used to provide a very fast, sensitive, and reproducible method for the analysis of CSF constituents, using only nanoliter volumes of sample (5 ). Furthermore, on line detection of the separated constituents, using UV absorption, allows accurate quantitation.
