Fluorometric quantitation of glutamine in cerebrospinal fluid

We describe a rapid, relatively simple-procedure for fluorometry of glutamine in cerebrospinal fluid. Glutamine is de-aminated with diluted sulfuric acid at 100 degrees C. The ammonia liberated is then reacted with a buffered o-phthalaldehyde--mercaptoethanol solution, pH 7.4, to form a fluorochrome. Fluorescence is linearly related to the concentration of glutamine from 0.10 to 0.60 g/L (0.68 to 4.10 mmol/l). To prevent interference by endogenous ammonia, each specimen was corrected for its own background fluorescence. The mean analytical recovery was 99.8%. Within-day variation (CV) for pooled, enriched cerebrospinal fluid controls at 0.33 g/L (2.22 mmol/L) and 0.53 g/L (3.63 mmol/L) were 2.2 and 5.1%. Day-to-day variation (CV) for the same controls was 4.4 and 4.8%, respectively. Data obtained by our method correlate excellently (r = 0.980) with those by an established procedure based on the Berthelot (phenol--hypochlorite) reaction.