Simultaneous Determination of Taurine, N-Acetylcysteine, Glycine and Methionine in Commercial Formulations by High-Performance Liquid Chromatography

A simple, inexpensive, reliable, selective and sensitive liquid chromatographic method was developed and validated for the simultaneous quantification of taurine (Tau), N-acetylcysteine (NAC), glycine (Gly) and methionine (Met) and applied for the first time to the analysis of commercial alimentary supplements. The amino acids (AAs) were analyzed after labeling reaction with 2,4-dinitrofluorobenzene (DNFB) in the presence of cetyltrimethylammonium bromide (CTAB). The derivatization reaction conditions were optimized and the derivatives were separated on a Phenomenex Synergi MAX-RP 4 μm stainless steel column under gradient elution conditions. A mixture of triethylammonium (TEA) phosphate buffer (pH 3) and acetonitrile under gradient elution conditions was used as mobile phase at a flow rate of 0.4 mL/min, UV absorbance detection was set at λ = 360 nm. Linear responses were obtained (determination coefficient ≥ 0.9996). Intra-day precision (RSD) was ≤ 1.71% for corrected peak area ratio (AA to internal standard) and ≤ 0.55% for retention times (t) without significant differences between intra- and inter-day data. Recovery studies showed good results for all the examined compounds (from 99.26 to 99.90%; RSD ≤ 1.29%) %) with RSD ≤ 1.29%. The method was found to be specific and sensitive. The method can be useful for the quality control of commercial products.