高压密闭消解-氢化物发生原子荧光光谱法测定农作物中硒的含量

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

提出了高压密闭消解-氢化物发生原子荧光光谱法测定农作物中硒含量的方法。粮食类样品(干样)去除杂物后,用水洗净,于60℃烘干;蔬菜类样品(鲜样)用水洗净,晾干,取可食用部分,制成匀浆。取上述样品0.5000 g置于高压密闭聚四氟乙烯(PTFE)内罐中,加入8 mL硝酸和2 mL 30%(质量分数)过氧化氢溶液,混匀过夜,于150℃密封消解4 h。冷却至室温后,于150℃赶酸至约1 mL,加入50%(体积分数)盐酸溶液5 mL,于150℃继续保持加热至溶液无色清亮并伴有白烟冒出。冷却后转移至10 mL容量瓶中,加入100 g·L^(-1)铁氰化钾溶液2.5 mL,用水定容。所得溶液在硒高性能空心阴极灯电流为80 mA,载气流量为300 mL·min^(-1),屏蔽气流量为700 mL·min^(-1)的条件下,采用氢化物发生原子荧光光谱法测定其中硒的含量。结果表明,硒的质量浓度在100μg·L^(-1)以内与对应的荧光强度呈线性关系,检出限(3s)为0.001 mg·kg^(-1)。方法用于国家标准物质分析,测定值的相对标准偏差(n=12)为2.3%~7.1%,相对误差为-6.7%~9.7%。方法还用于实际样品分析,所得测定结果与国家标准GB 5009.93-2017基本一致。

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(0.5000 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 100μg·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.