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).

Salting-out assisted liquid-liquid extraction and partial least squares regression to assay low molecular weight polycyclic aromatic hydrocarbons leached from soils and sediments.

A novel method was developed to determine low molecular weight polycyclic aromatic hydrocarbons in aqueous leachates from soils and sediments using a salting-out assisted liquid-liquid extraction, synchronous fluorescence spectrometry and a multivariate calibration technique. Several experimental parameters were controlled and the optimum conditions were: sodium carbonate as the salting-out agent at concentration of 2molL-1, 3mL of acetonitrile as extraction solvent, 6mL of aqueous leachate, vortexing for 5min and centrifuging at 4000rpm for 5min. The partial least squares calibration was optimized to the lowest values of root mean squared error and five latent variables were chosen for each of the targeted compounds. The regression coefficients for the true versus predicted concentrations were higher than 0.99. Figures of merit for the multivariate method were calculated, namely sensitivity, multivariate detection limit and multivariate quantification limit. The selectivity was also evaluated and other polycyclic aromatic hydrocarbons did not interfere in the analysis. Likewise, high performance liquid chromatography was used as a comparative methodology, and the regression analysis between the methods showed no statistical difference (t-test). The proposed methodology was applied to soils and sediments of a Brazilian river and the recoveries ranged from 74.3% to 105.8%. Overall, the proposed methodology was suitable for the targeted compounds, showing that the extraction method can be applied to spectrofluorometric analysis and that the multivariate calibration is also suitable for these compounds in leachates from real samples.