Determination of thallium traces by ETAAS after on-line matrix separation and preconcentration in a flow injection system

A simple and sensitive flow injection system was developed for separation, preconcentration and determination of thallium. Preconcentration is based on the analyte sorption on a microcolumn of dibenzo-18-crown-6(DB18C6) immobilized on surfactant coated alumina with subsequent elution using a nitric acid solution (500 mu L, 2 mol L-1). The concentration of thallium in the eluent was determined using electrothermal atomic absorption spectrometry. Factors influencing the sorption and desorption of thallium ion were investigated. Using a sample volume of 5 mL, the calibration was linear from 0.1 to 20 mu g L-1 range (r = 0.9996) with a detection limit of 0.05 mu g L-1. The maximum sorption capacity was 1432 mu g of thallium per gram of sorbent. The precision of the method at 1 mu g L-1 was 5.7% RSD (n = 11). The method was applied for determination of thallium in water, hair, nail, and standard reference samples. The accuracy was assessed using addition-recovery experiment or by comparison of the results with certified reference materials.