ONLINE ION-EXCHANGE SYSTEM COUPLED TO INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION SPECTROMETER WITH ULTRASONIC NEBULIZATION FOR THE SEPARATION, PRECONCENTRATION AND DETERMINATION OF ARSENIC(V) AND MONOMETHYLARSONATE

An on-line ion exchange preconcentration system has been developed for the separation and determination of the arsenic species, monomethylar sonate (MMA) and As(V) by inductively coupled plasma atomic emission s pectrometry (ICP-AES). The strongly basic anion-exchange resin AG1-X8 was used for the separation of these two arsenic species, which were n early quantitatively recovered by a sequential elution with 0.05 M sod ium acetate-0.05 M acetic acid and 1 M HCl, respectively. The pH and t he now rate of the sample and the eluents, as well as the flush time o f the spectrometer and the enrichment factors were studied in order to achieve quantitative retention-elution conditions, to optimize the on -line coupling of the preconcentration system to the ICP instrument an d to reach detection limits as low as possible. Without using a hydrid e generation system, the optimised coupling of these two systems toget her with the use of an ultrasonic nebulizer allows to reach detection limits for the As determination in the range of ng l(-1). The system p rovides complete automation of sample retention, elution and regenerat ion of the resin. The described method could be applied to the determi nation of MMA and As(V) in synthetic As mixtures, simulating an extrac t of a marine sediment and to the separation, preconcentration and det ermination of As(V) in BCR standard reference materials, such as sludg es and soils.