A simple fluorometric method for the determination of serum free carnitine

A new fluorometric method for the determination of serum free carnitine is described. The addition of carnitine to a system containing carnitine acetyltransferase (EC 2.3.1.7) and acetyl-CoA gives rise to the formation of CoA. The system is coupled to N-(p-(2-benzimidazolyl)-phenyl)-maleimide (BIPM). A fluorescent agent, CoA-BIPM, is produced proportionally to concentration of carnitine. By measuring the fluorescence intensity of BIPM, the carnitine content of serum can be determined. The coefficients of variation, within-run and between-run, of the method were 5.2 and 2.6%, respectively. Recovery of carnitine added to serum was 98-113%. Comparison with a colorimetric method showed a good correlation (r greater than 0.90). The method has sufficient sensitivity to measure concentrations as low as 10 mumol/l.