Determination of Selenium in Crops by Hydride Generation Atomic Fluorescence Spectrometry with High Pressure Sealed Digestion

A method for the determination of selenium in crops by hydride generation atomic fluorescence spectrometry with high pressure sealed digestion was proposed. After removing impurities, the grain samples (dry samples) were washed with water and heated to dryness at 60 ℃. The vegetable samples (fresh samples) were washed with water and dried, and the edible portion was taken to make a homogenate. The above sample (0.500 0 g) was taken and placed in a high pressure sealed PTFE inner tank, adding 8 mL of nitric acid and 2 mL of 30% (mass fraction) hydrogen peroxide solution. After mixing well for overnight, the mixture was sealed and digested at 150 ℃ for 4 h. After cooling to room temperature, the solution was drived acid to about 1 mL at 150 ℃, adding 5 mL of 50% (volume fraction) hydrochloric acid solution. The solution was heating at 150 ℃ until it was colorless and clear with white smoke. After cooling, it was transferred to a 10 mL-volumetric flask and 2.5 mL of 100 g·L^-1 potassium ferricyanide solution was added. Water was used to make its volume up to 10 mL. Selenium in the obtained solution was determined by hydride generation atomic fluorescence spectrometry under the conditions of 80 mA of selenium high performance hollow cathode lamp current, carrier gas flow at 300 mL·min^-1 and shielding gas flow at 700 mL·min^-1. As shown by the results, linear relationship between the fluorescence intensity and mass concentration of selenium was found within 100 μg·L^-1, with detection limit (3s) of 0.001 mg·kg^-1. This method was applied to analysis of the national reference materials, with RSDs (n=12) of the determined values in the range of 2.3%-7.1%, and the relative error in the range of -6.7%-9.7%. This method was also used for analysis of the actual samples, and the determined results obtained were basically consistent with those by national standard GB 5009.93-2017.