Magnetic Solid Phase Extraction Coupled With Atomic Spectrometry For The Analysis Of Trace Heavy Metals

Atomic absorption spectrometry and atomic emission spectrometry are routine methods for trace and ultratrace heavy metals analysis. At present, many research works on atomic absorption spectrometry and atomic emission spectrometry are mainly concentrated on the hyphenated technique, such as capillary electrophoresis, gas chromatography, high performance liquid chromatography (HPLC), hydride generation and online preliminary enrichment coupling with atomic absorption/emission spectrometry. Hyphenated technique has expanded the application of atomic absorption/emission spectrometry and improved the sensitivity. Magnetic solid phase extraction and hydride generation can realize enrichment for analyte before determination, thus the hyphenated technique greatly improve the analysis sensitivity.Cadmium and lead can accumulate in the human body, the quantity once more than the body’s tolerances may result various organs lesions. With constantly improving of food safety awareness, people pay more and more attention on toxic pollution in food. Heavy metal content has become an important indicator of food safety. It is important to Accurate detect the toxic heavy metal content in drinking water and food accurately.In this paper, magnetic solid phase extraction coupled with microwave plasma torch atomic emission spectrometry (MSPE-MPT-AES) for the determination of trace cadmium in water, cigarette and cigarette smoke and magnetic solid phase extraction-tubular flow magnetic separation combined with hydride generation coupled with electrothermal atomic absorption spectrometry (MSPE-HG-ETAAS)for the determination of trace lead in soy bean products were developed. The main contents and results were shown as follows:1. Trace cadmium determination of drinking purified water, natural drinking water, natural mineral spring water and tap water by MSPE-MPT-AES has been developed. The Fe3O4 magnetic nanoparticles (MNPs) were prepared by chemical coprecipitation. Silica was coated on the surface of magnetic nanoparticles by ammonia catalyzing of tetraethyl silicate (SMNPs). EDTA was bound on the surface of the magnetic nanoparticles containing silicate by esterification reaction, thereby Fe3O4 magnetic nanoparticles were functionalized by EDTA (EDTA-SMNPs). The EDTA-SMNPs were used as adsorption material for cadmium in water samples. The adsorption capacity of the EDTA-SMNPs for Cd2+ was 49.54 mg/g and the EDTA-SMNPs can be reused for 6 times. The linear range of the calibration curve for cadmium was from 0.2 to 100μg/L with correlation coefficient of 0.9998. The detection limit for Cd2+ was observed as 41 ng/L (n=11,3σ) with enrichment factor of 200. The relative standard deviation (RSD, n=11) was 1.14% at 10μg/L. The recoveries for the spiked samples were in the range of 98.7%～103%.2. The cadmium determination in cigarette and its smoke were developed using MSPE-MPT-AES. EDTA-SMNPs used as magnetic solid phase extraction adsorbent for Cd2+ The detection limit (LOD,3a) for Cd based on an enrichment factor of 200 was 41 ng/L and the linearity range was between 0.2 and 100μg/L with correlation coefficient of 0.9998. The relative standard deviation (RSD, n= 11) was 1.14% at 10μg/L. The samples were digested by nitric.acid-perchloric acid digestion system.Cd content were found between 1.247 and 5.168 μg/g in the analyzed four types flue-cured tobacco cigarette, more than 53.65% of total amount of Cd in its smoke. The recoveries for the spiked samples were in the range of 94.60%-100.7%. The proposed method is simple, low cost, sensitive and easy easy to popularize.3. Magnetic solid phase extraction-tubular flow magnetic separation combined with hydride generation coupled with electrothermal atomic absorption spectrometry (SPE-FMS-HG-ETAAS) for the determination of trace lead in instant soybean drink, soymilk, yuba, soy bean and soya-bean milk was developed. The detection limit for Pb2+ was observed as 3.62 ng/L. The linear range of the calibration curve for lead was found between 10 and 500 ng/L with correlation coefficient of 0.9991. The relative standard deviation (RSD, n=11) was less than 4.2% at 100 ng/L. The recoveries for the spiked samples were in the range of 94.95% ～103.2%. The proposed method was simple, fast with good selectivity and high sensitivity.