Solid-Phase Extraction of As(III) from Aqueous Samples Using On-Column Formation of As(III)-Trispyrrolidinedithiocarbamate

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Abstract
Two methods are presented for the selective preconcentration of As(III) by using complexation-type stationary phases. These phases are prepared: (1) by loading a C18-bonded silica with the cetyltrimethylammonium-pyrrolidinedithiocarbamate (CTA+-PDC−) ion-pair, or (2) by converting a strong anion-exchange (SAX) resin from the quaternary ammonium form into the pyrrolidinedithiocarbamate (PDC−) form. When As(III)-containing solutions are passed through such stationary phases, the immobilized PDC− yields the non-polar As(III)-trispyrrolidinedithiocarbamate (As(PDC)3) which is retained on the non-loaded second part of the C18 cartridge (method 1), or on an unloaded C18 cartridge coupled in series with the SAX cartridge (method 2). For both methods parameters influencing the preconcentration have been investigated by using the 74As(III) radiotracer; 74As(V) was applied to study the selectivity of both methods. A selective preconcentration of As(III) is possible. The retention mechanisms are discussed. After optimization, the applicability was tested by determining As(III) in some real water samples. To this end the As(PDC)3 was eluted from the C18 cartridges with acetone, followed by evaporation and redissolution in a suitable solvent for hydride generation atomic absorption spectrometry (HGAAS). Arsenic can be determined in both fresh water and seawater satisfactorily with a detection limit of about 0.02ng ml− 1