微波等离子体原子发射光谱分析膨润土中总砷的研究

doi:10.3964/j.issn.1000-0593(2021)12-3671-05

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Abstract Bentonite is natural clay of layered phyllosilicates, composed of Si—O tetrahedral and Al—O octahedral sheets in the ratio of 2∶1. Its vesicular structure, chemical composition, exchangeable ion type and small crystal size result in unique properties including large chemically active surface area, high cation exchange capacity and high porosity. It is widely used in petrochemical, metallurgy, food, medicine, environmental protection and other fields. As an element, bentonite may pose a potential risk to human health during the development and utilization of bentonite. This paper determined the total As content in bentonite by microwave plasma atomic emission spectrometry (MP-AES) combined with multimode sample introduction system (MSIS). Nitric acid, hydrochloric acid and hydrofluoric acid were used for microwave digestion of bentonite. After adding perchloric acid, the digestion solution was dissolved at low temperature on an electric heating plate. 25% (w/v) potassium iodide solution was used as prereduction solution to reduce As(Ⅴ) to As(Ⅲ), and sodium borohydride/sodium hydroxide was used to transform As(Ⅲ) into gaseous hydride (AsH₃) in the MSIS. By optimizing the best viewing position and nebulizer gas flow of MP-AES, the best analytical performance of As measurement is achieved. The interference of spectral lines overlapping was avoided by selecting 188.979 nm as the analytical wavelength of As. The background interference was corrected by the fast linear interference correction (FLIC) model. The matrix effect was corrected by selecting 261.542 nm as the wavelength of the internal standard element Lu. The limit of detection (LOD) of As is 0.41 μg·L^-1. The analysis method was evaluated by the determination of national standard reference materials. The determination value of As was consistent with the certified value of standard reference material, and the relative standard deviation (RSD) was less than 2.80%, which verified the accuracy and precision of the method. The analysis of 12 bentonite samples from different places in China showed that the total As concentration was relatively low (the average content of As was between 3.51～12.6 mg·kg^-1). Based on the limits set by the National Standard of the People’s Republic of China GB 2760—2014 food safety national standard food additive bentonite, the As content in all samples did not exceed the standard. MP-AES using atmospheric nitrogen as the plasma source reduces the operation cost, improves the analysis efficiency, and provides a reliable method for the quality control of bentonite. It has the advantages of safe and stable operation, simple and rapid operation and strong applicability.

Key words：Bentonite; Microwave plasma atomic emission spectrometry; Total As; Hydride generation; Fast linear interference correction

Received: 2020-12-01 Accepted: 2021-03-06

ZTFLH:

O657.3

Corresponding Authors: FU Liang E-mail: fuliang@vip.163.com

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2021)12-3671-05 OR https://www.gpxygpfx.com/EN/Y2021/V41/I12/3671