Determination of Chromium(III)and Chromium(VI) by Electrothermal Atomic Absorption Spectrometry after Separation and Preconcentration with Ion Exchange Resins
A sensitive and selective method for the determination of ppb levels of chromium (III) and chromium (VI) in water, based on preconcentration writh a mixture of finely pulverized chelating exchange resin and anion-exchange resin beads has been investigated by electrothermal atomic absorption spectrometry (ETAAS). A sample solution containing 0.1-2.0μg of both chromium (III) and chromiunl (VI) was placed in a polyethylene beaker; then, 20 mg of anion-exchange resin beads (ARB) and 1ml of finely pulverized chelating exchange resin suspension (CRS) were added at pH 6. The solution was stirred for 20 min and filtered under suction through a glass filter, and the ARB were placed on the pasted surface of a cel1ophaned tape, fixed by sticking another tape on them, and then divided into several sets of six ARB by cutting with ceramics scissors. A sets of six ARB was inserted into a cup-type cuvette for the determination of chromiunl (VI) by ETAAS. The filtrate was then filtered under suction through a membrane filter. A thin circular resin, which was retained on a membrane filter, was fixed by sticking directly with a cellophaned tape and divided into several 3 mm diameter disks by punching. Each disk was used for the deternination of chromium (III) by ETAAS. The effects of commonly occurring foreign ions were investigated. The proposed method based on preconcentration with the exchange resins will be applied to the determination of chromium (III) and chromium (Vl) in water samples
