Determination of thallium in water by electrothermal AAS with the direct injection of a cellulose nitrate resin suspension used for solid-phase extraction

A cellulose nitrate resin (CNR) suspension was prepared by pouring a mixture solvent of dichloromethane and tetrahydrofuran (2 : 1) containing cellulose nitrate into an aqueous solution of benzalkonium chloride under vigorous stirring, volatilizing dichloromethane and tetrahydrofuran at about 98degreesC, and concentrating the suspension with by centrifugation. The resulting suspension was used for the solid-phase extraction (SPE) of thallium(III) in water. The surface of CNR was supposed to be positively charged because of a remaining benzalkonium ion. It was found that thallium(III) was extracted from dilute hydrochloric acid (pH 1.6) to CNR added as a resin suspension to a sample solution, presumably as its chloride complex. The presence of ammonium pyrrolidinedithiocarbamate improved the extraction yield. Thallium(1) was not extracted without the addition of bromine water. After SPE, CNR was collected on a membrane filter by filtration under suction, was suspended again in 1.0 ml of 10 mM HNO3 with ultrasonication, and then was injected directly into an electrothermal atomic absorption spectrometer. A linear calibration graph was obtained in the range 0 similar to 30 ng Tl-III using 50 ml of a sample solution. The detection limit, based on three times the standard deviation of the blank, was 0.9 ng (18 pg ml(-1)). The repeatability was examined using 50 ml of a sample solution containing 30 ng of Tl-III. The relative standard deviation was 2.5% (n = 5). The recovery of 30 ng of Tl(III) from 50 ml of a river water sample was 95 +/- 3% (n = 3).