Fast methods for simultaneous determination of arginine, ascorbic acid and aspartic acid by capillary electrophoresis.

Arginine (ARG), ascorbic acid (ASC) and aspartic acid (ASP) are very popular and widely consumed active ingredients used for fatigue treatment or improvement of physical performance. For this reason, these compounds are usually available in the same pharmaceutical formulation. In the current paper, we describe for the first-time methods for simultaneous determination of ARG, ASC and ASP using capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D) and with UV spectrophotometric detection (CE-UV). The proposed methods are simple, rapid (78 and 23 injections h^-1, respectively) and have low environmental impact (minimal waste generation). The separation by CE-C⁴D was achieved with a background electrolyte (BGE) composed by 20 mmol L^-1 N-tris(hydroxymethyl)- methyl]-3-aminopropanesulfonic acid (TAPS) and 10 mmol L^-1 of NaOH (pH 8.7). The limits of detection (LOD) were 0.01, 0.02 and 0.04 mmol L^-1 for ARG, ASC and ASP, respectively. The proposed CE-UV method was optimized with a BGE composed by 10 mmol L^-1 sodium tetraborate (pH 9.4). The limits of detection (LOD) were 0.03, 0.02 and 0.04 mmol L^-1 for ARG, ASC and ASP, respectively. No statistically significant differences were observed (95% confidence level) between the results obtained by the developed CE methods and reference procedures (HPLC for ARG, iodometry for ASC and, acid-base titration for ASP).