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).

A sub-minute electrophoretic method for simultaneous determination of naphazoline and zinc.

This paper reports for the first time, a method for simultaneous determination of naphazoline (NPZ) and zinc (Zn) using an analytical separation technique (capillary electrophoresis with capacitively coupled contactless conductivity detection -CE-C4D). A single run is possible every 55s (sampling rate=65h-1). The separation by CE-C4D was achieved on a fused silica capillary (50cm length - 10cm effective, 50µm i.d.) with a background electrolyte (BGE) composed by 20mmolL-1 of 2-(morpholin-4-yl)ethane-1-sulfonic acid (MES) and 20mmolL-1 of histidine (HIS) (pH 6.0). Detection limits were estimated at 20 and 30µmolL-1 and recovery values for spiked samples were 98 and 102% for NPZ and Zn, respectively. The developed procedure was compared to HPLC (NPZ) and FAAS (Zn) and no statistically significant differences were observed (95% confidence level).