Department of Analytical Chemistry and Food Science, University Institute of Materials, Faculty of Science, University of Alicante, P.O. Box 99, 03080, Alicante, Spain.
Department of Analytical Chemistry and Food Science, University Institute of Materials, Faculty of Science, University of Alicante, P.O. Box 99, 03080, Alicante, Spain.
Talanta. 2020 Dec 1;220:121395. doi: 10.1016/j.talanta.2020.121395. Epub 2020 Jul 15.
In this study, a sensitive and matrix-effect free analytical method for Cd determination in engine oils and fuel samples by dispersive liquid-liquid microextraction with electrothermal atomic absorption spectrometry has been successfully developed. The extractant solvent used for the microextraction procedure was a magnetic ionic liquid (MIL) (i.e., bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate (II) [Emim][Co(SCN)]), which presents a paramagnetic property, and allows an easy phase separation using a magnet. In order to eliminate the well-known drawbacks of direct introduction of MIL in the graphite furnace, a back-extraction procedure was performed to transfer the analyte into an aqueous phase. The main experimental factors affecting the extraction of Cd (i.e., amount of sample and MIL, extraction and back-extraction time and concentration and amount of nitric acid) were optimized using a multivariate analysis consisting in two steps: a Plackett-Burman design followed by a circumscribed central composite design. Under optimum conditions (i.e., amount of sample: 6.2 g; amount of MIL: 119 mg; extraction time: 1 min; amount of nitric acid: 200 mg; nitric acid concentration: 1 mol L and back-extraction time: 1 min), the proposed analytical method was validated and successfully used to analyze three real-world samples (i.e., used engine oil, gasoline and diesel). The three samples were spiked at two levels (i.e., 10 and 20 μg kg of Cd for used engine oil and 1 and 3 μg kg of Cd for gasoline and diesel). RSD and recovery values were within the range of 6-11% and 95-110%, respectively.
本研究成功开发了一种灵敏且无基质效应的分析方法，用于通过分散液-液微萃取结合电热原子吸收光谱法测定发动机油和燃料样品中的 Cd。用于微萃取程序的萃取溶剂是一种磁性离子液体（MIL）（即双（1-乙基-3-甲基咪唑）四硫氰酸钴（II）[Emim][Co（SCN）]），具有顺磁性，可使用磁铁轻松进行相分离。为了消除直接将 MIL 引入石墨炉中所带来的众所周知的缺点，进行了反萃取程序，将分析物转移到水相中。使用包含两步的多元分析（即 Plackett-Burman 设计和限定中心复合设计）优化了影响 Cd 萃取的主要实验因素（即样品量和 MIL 量、萃取和反萃取时间以及硝酸的浓度和量）。在最佳条件下（即样品量：6.2 g；MIL 量：119 mg；萃取时间：1 分钟；硝酸量：200 mg；硝酸浓度：1 mol·L 和反萃取时间：1 分钟），验证了所提出的分析方法，并成功用于分析三个实际样本（即使用过的发动机油、汽油和柴油）。这三个样品在两个水平上进行了加标（即对于使用过的发动机油，Cd 的加标量为 10 和 20 μg·kg；对于汽油和柴油，Cd 的加标量为 1 和 3 μg·kg）。RSD 和回收率值分别在 6-11%和 95-110%的范围内。
