| For fast and accurate digestion of vegetable oil and determination of the contents of Pb, Cd and Cr in it with low cost, carbonization-wet digestion-graphite furnace atomic absorption spectrometry(GFAAS) was adopted in the determination of Pb, Cd and Cr in 219 vegetable oil samples (134 edible oil samples and 85 seasoning oil samples) of 12 types after comparing digestion acid and sample amounts, optimization ashing temperature and atomization temperature, and comparing digestion method and the RSDs of the ICP-OES, ICP-MS, and GFAAS. Quality control was also carried out in the manner of standard recovery. The results showed that vegetable oil could be completely digested under the conditions of sample amount 0.200 0 g , nitric acid 13 mL and hydrogen peroxide 5 mL. The Pb and Cd were determined using the deuterium lamp, and the Zeeman background was used to determine Cr. The optimal instrument conditions were obtained as follows: ashing temperature of Pb, Cd and Cr 400, 300, 1 400?℃ and atomization temperatures of Pb, Cd and Cr 1 100, 800, 2 000?℃. The standard recovery was in the range of 94.6%-109.3%. The average contents of Pb, Cd and Cr in edible oils were 0.052 2, 0.001 0 mg/kg and 0.331 7 mg/kg, respectively, and the average contents in seasoning oils were 0.192 5, 0.003 7 mg/kg and 1.813 8 mg/kg. The contents of Pb, Cd and Cr in seasoning oils were generally higher than those in edible oils. The carbonization-wet digestion-GFAAS had advantages of high precision and reliability in the determination of Pb, Cd and Cr and it was the preferred method for batch determination of Pb, Cd and Cr in vegetable oil. |
