Analysis of Human Cerebrospinal Fluid by Capillary Electrophoresis with Laser-Induced Fluorescence Detection

Capillary electrophoresis with laser-induced fluorescence detection is used to analyze 10 µL samples of human cerebrospinal fluid. Primary amine-containing compounds in untreated cerebrospinal fluid are labeled with 3-(4-carboxy- benzoyi)-2-quinolinecarboxaldehyde prior to analysis, producing fluorescent isoindoles. Electropherograms containing approximately 50 peaks are obtained in less than 35 min from cerebrospinal fluid samples. Ten peaks in the electropherograms have been identified and quantitated: arginine, glutamine, threonine, valine, γ-amino-n-butyric acid, serine, alanine, glycine, glutamic acid, and aspartic acid. Detection limits for these 10 amino acids range from 0.29 nM for γ-amino-n- butyric acid to 100 nM for threonine, and separation efficiencies as high as 190 000 theoretical plates are obtained for these analytes. Electropherograms of cerebrospinal fluid samples from patients with Alzheimer's disease and from children with different neurological disorders are compared to those of healthy controls. Differences in individual amino acid levels are observed between the patient groups, and these differences appear to be disease and age related. These results indicate that analysis of cerebrospinal fluid by capillary electrophoresis will be useful as a selective, rapid, and sensitive tool for both diagnosis of central nervous system disorders and for study of the mechanisms of these disorders.