Determination of arsenic species by field amplified injection capillary electrophoresis after modification of the sample solution with methanol

Organic solvent modification is investigated as a simple and effective way to decrease the conductivity of Liquid samples containing anionic As specie s, making them suitable for field amplified sample stacking capillary elect rophoresis (CE) measurements with direct UV detection. Experimental variabl es that influence the procedure, as buffer pH, stacking and running potenti al, are described for methanol, selected as the optimum sample modifier. Th e influence of modifying the CE buffer with methanol on the resolution is a lso discussed. Results of stacking with and without removing the sample mat rix from the capillary (with and without polarity switching after the stack ing stage) are reported. The optimized method permits the determination of As(III) (arsenite), free As(V) (arsenate), and dimethylarsinate (DMA), in t he range from 0.5 to 20 mg/l, with detection limits around 0.3 mg/l. For ot her As(V) compound of human origin, phenylarsonate (PAA), and p-aminobenzen earsonate (PABA), the power of detection is higher due to their higher exti nction coefficients. The linear range extends from 20 to 1000 mu g/l, with a detection limit of 11 mu g/l (PAA) and 16 mu g/l (PABA). (C) 1999 Elsevie r Science B.V. All rights reserved.