Determination of linear alkylbenzenesulfonates (LASs) in sewage sludge and carrots by capillary electrophoresis--UV detection.

A method based on capillary zone electrophoresis has been proposed in order to separate and determine four groups of linear alkylbenzenesulfonates in sewage sludge and carrots. The separation was carried out in a silica capillary of 50 cm x 75 microm at 25 kV using a sodium borate buffer solution of 100 mM which includes 40% of acetonitrile. The detection was made by UV-Vis diode array detector. Precision, accuracy, linearity, detection and quantification limits of the method were determined. Finally, the method was applied to analyse samples of sewage sludge from a wastewater depuration station in Crispijana (Alava, Spain) and carrots sown in soils spiked with this sludge. In this case, it is necessary to carry out an extraction step for its determination. The extraction was carried out by solid phase extraction with a C18 cartridge. The solid phase extraction (SPE) parameters were also optimized and the recoveries were calculated. Samples of sewage sludge were analysed weekly during two years and, in all cases, results under legal limits for their use in agriculture were obtained.

Stripping voltammetric and polarographic techniques for the determination of anti-fungal ketoconazole on the mercury electrode.

The electroanalytical behaviour of ketoconazole in Britton-Robinson buffer is described. The reduction process on the hanging mercury drop electrode (HMDE) gives rise to one peak over -1.6 V (vs. Ag/AgCl/sat.KCl), within the pH range studied (4.7-9.6). The results showed that the reduction of ketoconazole is irreversible and the limiting current is adsorption controlled. The dependence of the peak current on the concentration was studied by means of different polarographic and voltammetric techniques. Using adsorptive stripping differential pulse voltammetry (AdS-DPV), the detection limit (DL) reached was 5.3 x 10(-11) mol l(-1). Two procedures, based on differential pulse polarography (DPP) and AdS-DPV in aqueous medium were developed for the determination of ketoconazole in a gel formulation and spiked urine samples, respectively.