HG-AFS Determination of Mercury in Rubber and Its Products with Microwave Assisted Sample Digestion

The rubber sample was smashed with a frozen grinder, and a portion of 0.2 g of sample was taken and digested with 6 mL of HNO3 and 2 mL of H2O2 in a closed PTFE digester. The solution obtained was made up to 50 mL, and an aliquot of 5.00 mL after diluting to 10 mL with HCl(5+95) was used for HG-AFS determination of its Hg-content. Analytical conditions were optimized as follows: ① 0.5 g·L-1 solution of KBH4 dissolved in 2 g·L-1 NaOH solution was used as reductant; ② HCl(5+95) solution was used as carrier; ③ negative high voltage of photomultiplier: 260 V; ④ lamp current: 15 mA; ⑤ height of atomizer: 10 mm; ⑥ flow-rate of carrier gas and shielding gas: 300, 800 mL·min-1 respectively. Detection limit (3s/k) found was 3 μg·L-1. Value of average recovery found by standard addition method was 95.7%, with RSD (n=11) of 4.3%. Accuracy and precision of this method were further verified by an inter laboratory program among 10 laboratories, and satisfactory results were obtained.