Direct determination of trace amounts of tin in titanium dioxide by slurry introduction/graphite furnace AAS

An analytical method for the determination of trace amounts of tin in titanium dioxide was investigated using slurry introduction and direct atomization graphite furnace AAS. A sample powder (0.5 g) was placed in a glass vessel (50 ml), and mixed well with 2.5 ml of 0.1% sodium hexametaphosphate by an ultrasonic agitator (for 15 min). The resultant solution was transferred to a 50 ml volumetric flask, diluted to the mark with water, and finally shaken for 20 min. Ten microliters of L-ascorbic acid (20% solution) and, subsequently, sample slurry, were introduced into a tantalum carbide-coated tube by a micropipet. The optimum atomization conditions were as follows: drying-1 at 80120°C (30 s), drying-2 at 120160°C (30 s), ashing at 800°C (30 s), atomizing at 2800°C (10 s) and cleaning at 3000°C (3 s). A calibration curve was made by adding standard solutions of tin to the sample slurry in the graphite tube. Fairly large interference from titanium dioxide with the tin determination was almost eliminated by the proposed technique. The results for tin in some samples of titanium dioxide by the present method agreed well with those values obtained by hydride generation(HG)/AAS or ICP-MS after acid decomposition. The lower limit (100.) of the determination of tin by the present method was 0.15 ng, which corresponded to 1.5 μg/g in the sample; the relative standard deviations (n = 10) for 1 ng of tin was 1.6%.