Abstract

The total selenium content of selenium-enriched agricultural products was determined by inductively coupled plasma mass spectrometry after microwave digestion. The total selenium content in the tested samples ranged from 27.9 μg/kg to 13.6 mg/kg. High performance liquid chromatography–inductively coupled plasma mass spectrometry was employed to determine selenite and selenate in selenium-enriched rice, tea, and garlic. The separation of inorganic and organic selenium was realized within 15 min by using 40 mmol/L diammonium phosphate (pH 5.0) and 60 mmol/L diammonium phosphate (pH 6.0) as the mobile phase with gradient elution. Selenite and selenate were isolated by ultrasonic assisted extraction at 78 °C for 30 min with 0.1 mol/L potassium hydroxide as the extraction solution. The detection limits were 2.5 and 5 μg/kg for selenite and selenate, respectively. The relative standard deviation was less than 5.5%. Recoveries of inorganic selenium were between 88.2% and 113.0%. The proposed method was successfully applied for the determination of inorganic selenium as well as total selenium in selenium-enriched rice, tea, and garlic. The results showed that inorganic selenium in natural selenium-enriched agricultural products is primarily present in selenite composing no more than 20% of total selenium.

摘要

微波消解后，通过电感耦合等离子体质谱法测定富硒农产品的总硒含量。测试样品中的总硒含量为27.9μg/ kg至13.6 mg / kg。高效液相色谱-电感耦合等离子体质谱法用于测定富硒大米，茶和大蒜中的亚硒酸盐和硒酸盐。通过使用40 mmol / L磷酸氢二铵（pH 5.0）和60 mmol / L磷酸氢二铵（pH 6.0）作为流动相并进行梯度洗脱，在15分钟内实现了无机和有机硒的分离。在0.1 mol / L氢氧化钾为萃取液的条件下，于78°C超声辅助萃取30 min，分离出亚硒酸盐和硒酸盐。亚硒酸盐和硒酸盐的检出限分别为2.5和5μg/ kg，分别。相对标准偏差小于5.5％。无机硒的回收率在88.2％至113.0％之间。该方法已成功用于富硒米，茶和大蒜中无机硒以及总硒的测定。结果表明，天然富硒农产品中的无机硒主要存在于亚硒酸盐中，其含量不超过总硒的20％。