ABSTRACT
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 20â¯mmolâ¯L-1 N-tris(hydroxymethyl)- methyl]-3-aminopropanesulfonic acid (TAPS) and 10â¯mmolâ¯L-1 of NaOH (pH 8.7). The limits of detection (LOD) were 0.01, 0.02 and 0.04â¯mmolâ¯L-1 for ARG, ASC and ASP, respectively. The proposed CE-UV method was optimized with a BGE composed by 10â¯mmolâ¯L-1 sodium tetraborate (pH 9.4). The limits of detection (LOD) were 0.03, 0.02 and 0.04â¯mmolâ¯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).
ABSTRACT
Ascorbic acid and zinc are essential nutrients that play important roles in nutrition, immune support, and maintenance of health. For this reason, both compounds are widely used as ingredients in dietary supplements. We report, for the first time, an analytical method for fast simultaneous determination of ascorbic acid and zinc. A single analysis run is possible every 80 s (45 injections/h). The method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection using a fused silica capillary with 50 cm length (effective length of 10 cm). The separation was achieved by using a background electrolyte composed by 30 mmol/L of 2-(morpholin-4-yl)ethane-1-sulfonic acid and 30 mmol/L of histidine, pH 6.1. The detection limits were 10 and 20 µmol/L and recovery values for spiked samples were 101 and 100% for zinc and ascorbic acid, respectively. The results obtained with the developed procedure were compared to those obtained by titration (ascorbic acid) and flame atomic absorption spectroscopy (zinc), and no statistically significant differences were observed (95% confidence level).