Analytical Sciences

Microwave-assisted Extraction and Ion Chromatography Dynamic Reaction Cell Inductively Coupled Plasma Mass Spectrometry for the Speciation Analysis of Arsenic and Selenium in Cereals

Chia-Ying TSAI and Shiuh-Jen JIANG

Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan

An ion chromatography dynamic reaction cell inductively coupled plasma mass spectrometric (IC-DRC-ICP-MS) method for the speciation of arsenic and selenium compounds is described. Chromatographic separation was performed in a gradient elution mode using 0.5 mmol L⁻¹ ammonium citrate in 1% methanol (pH 4.5) and 15 mmol L⁻¹ ammonium citrate in 1% methanol (pH 8.0). The potentially interfering ³⁸Ar⁴⁰Ar⁺ and ⁴⁰Ar⁴⁰Ar⁺ at selenium masses of m/z 78 and 80 were reduced in intensity by approximately 3 orders of magnitude by using 1.0 mL min⁻¹ CH₄ as a reactive cell gas in the DRC. Arsenic was determined as the adduct ion ⁷⁵As¹²CH₂⁺ at m/z 89. The detection limits of the procedure were in the ranges of 0.006 – 0.009 ng As mL⁻¹ and 0.009 – 0.03 ng Se mL⁻¹, respectively. This method has been applied to determine various arsenic and selenium compounds in cereal samples. The accuracy of the method has been verified by comparing the sum of the concentrations of individual species obtained by the present procedure with the total concentration of elements. The arsenic and selenium compounds were quantitatively extracted with a Protease XIV and α-amylase solution in a microwave field at 70°C during a period of 30 min. The spike recoveries were in the range of 94 – 105% for all determinations.

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