High-Performance Liquid Chromatographic Analysis of Sarcosine as a Fluorescent Levofloxacin Derivative.

Sarcosine, N-methyl glycine, could be used as a biomarker for the diagnosis of prostate cancer. It exists in biosamples at low levels; therefore, sensitive methods are necessary for its detection. In this study, we developed a sensitive and selective method for the analysis of sarcosine, based on derivatizing sarcosine with a fluorescent reagent levofloxacin acyl chloride. The resulting derivative is highly responsive to a fluorimetric detector (lambda(ex) = 290 nm, lambda(em) = 460 nm). The sarcosine derivative can be separated from its molecular isomers (alpha-L-alanine, alpha-D-alanine and beta-alanine) on a hexyl-phenyl column by gradient elution using sodium acetate buffer (pH 3.8; 50 mM) and tetrahydrofuran as the mobile phase. The method showed a determination range of sarcosine in water over 44.5-1780.0 ng/mL (0.5-20.0 mu M) and the limit of detection at 8.9 ng/mL (0.1 mu M) (S/N 5 3 with 20 mu L injected). Intra-and inter-day precision (as % relative standard deviation) and accuracy (as % relative error) were all below 4.8%. Application of the method to the analysis of sarcosine in human urine proved feasible.