Determination of Cd in Edible Salt by Graphite Furnace Atomic Absorption Spectrometry

A method for the determination of Cd in edible salt by graphite furnace atomic absorption spectrometry was proposed. Edible salt sample (0.5 g) was dissolved and made its volume up to 50 mL with 1% (φ) nitric acid solution to prepare the test sample solution after shaking. 1% (φ) nitric acid solution was used as solvent, the matrix modifier containing 10 g·L^-1 ammonium dihydragen phosphate and 10 g·L^-1 ascorbic acid was obtained. Matrix modifier (1.0 μL) was absorbed into the test sample solution (20 μL) by an automatic sampler. The optimized heating conditions of graphite furnace were as follows: the drying temperature of 120 ℃, the ashing temperature of 350 ℃, the atomization temperature of 700 ℃, and the purification temperature of 2 700 ℃. As shown by the results, linear relationship between values of mass concentration of Cd and its absorbance was kept in the range of 0.1-2.0 μg·L^-1, with detection limits (3s/k) of 0.001 mg·kg^-1. Spiked solutions of sodium chloride containing different mass fractions of Cd were determined, and RSDs (n=6) of the determined values were less than 4.0%. Test for recovery was made on different types of edible salt samples by standard addition method, giving results in the range of 92.0%-101%.