ON-LINE 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

摘要

An on-line ion exchange preconcentration system has been developed for the separation and determination of the arsenic species, monomethylarsonate (MMA) and As(V) by inductively coupled plasma atomic emission spectrometry (ICP-AES). The strongly basic anion-exchange resin AG1-X8 was used for the separation of these two arsenic species, which were nearly quantitatively recovered by a sequential elution with 0.05 M sodium acetate-0.05 M acetic acid and 1 M HCl, respectively. The pH and the now rate of the sample and the eluents, as well as the flush time of 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 and to reach detection limits as low as possible. Without using a hydride generation system, the optimised coupling of these two systems together 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 provides complete automation of sample retention, elution and regeneration of the resin. The described method could be applied to the determination of MMA and As(V) in synthetic As mixtures, simulating an extract of a marine sediment and to the separation, preconcentration and determination of As(V) in BCR standard reference materials, such as sludges and soils. [References: 23]