Direct determination of s-carboxymethyl-l-cysteine in syrups by reversed-phase high-performance liquid chromatography

A simple reversed-phase high-performance liquid chromatography method was developed for the determination of s-carboxymethyl-l-cysteine in syrup preparations. The experiments were performed without specific sample pre-treatment. The LC conditions used were acetonitrile-10 mM sodium dihydrogenphosphate buffer, pH 2.0 (1:99, v/v) on a C₁₈ Inersil column with a flow rate of 1.5 ml/min. Ultraviolet detection was carried out at 240 nm. The method showed excellent linearity (r² > 0.9998) over the concentration range tested (0.8-25.6 mg/ml) with good precision and accuracy (%R.S.D. 0.7%). Recoveries were good (> 99%) with a limit of detection and limit of quantitation of 0.1 and 0.8 mg/ml. Other compositions in the syrup vehicle did not interfere the analysis of s-carboxymethyl-l-cysteine.