Speciation Analysis of Inorganic Selenium in Soil by High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry

Abstract

BACKGROUND In the speciation analysis of selenite Se (Ⅳ) and selenite Se (Ⅵ) in soil samples, the key problem is to select the extraction agents and detection methods. In the past, extraction agents may lead to Se species redistribution or cannot extract both Se (Ⅳ) and Se (Ⅵ). Selenium speciation has been routinely determined by Hydride Generation-Atomic Absorption Spectrometry (HG-AAS). However, Se (Ⅵ) cannot be directly measured and its concentration is calculated by the difference between analyzed total Se and Se (Ⅳ) concentrations. OBJECTIVES In order to establish an analysis method for the determination of Se (Ⅳ) and Se (Ⅵ) in soil samples by selecting the appropriate extraction agent and determination technique. METHODS The extraction capacity of different extraction agents was compared and 0.1 mol/L sodium hydroxide was selected for the experiment. Selenium species were quantitatively extracted in a ultrasonic field at 55℃ for 30 min. An analytical method for determination of Se (Ⅳ) and Se (Ⅵ) by High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry (HPLC-ICP-MS) was established. RESULTS The results show that Se (Ⅳ) and Se (Ⅵ) can be separated within 8 min by using a Hamilton PRP X-100 reversed-phase anion exchange column with 6 mol/L citric acid as mobile phase under pH of 5.5. The detection limits of Se (Ⅳ) and Se (Ⅵ) are 0.15 μg/L and 0.16 μg/L, respectively. Linear correlation coefficient (r2) is more than 0.999, the recoveries are 84.2%-95.8%, and the relative standard deviations are 1.4%-5.3% (n=6). CONCLUSIONS The proposed method is simple and fast and has good accuracy and high precision, which meets the requirements for analyzing inorganic selenium in soil.

Keywords

• soil
• selenite
• selenate
• sodium hydroxide
• high performance liquid chromatography-inductively coupled plasma-mass spectrometry