| Heavy metals are regarded as toxic inorganic pollutants which can’t be destroyed. They are long-term environmental contaminants, having a slow removal rate and large enrichment ratio. They could enrich in human body through food chain and do harm to the health of people. Therefore quick and accurate determinations of them are vital parts of analytical chemical studies.Analytical capabilities of inductively coupled plasma mass spectrometry(ICP-MS) was simultaneous, rapid, reliable and stable determination of trace and ultra-trace elements, however, the scopes of ICP-MS instruments were narrowed by their expensive cost. Because of its cheap cost, high selectivity and simplicity, flame atomic absorption spectrometry occupys an important position for the determination of heavy metals in food samples, however, the analysis of trace heavy metals often require separation and enrichment because of its low sensitivity. Main research contents are summarized as follows:(1) A new method was established which can detect nine kinds of heavy metals in food samples by ICP-MS.The objects of this portion are Pb, Cd, As, Sn, Ni, Cr, Cu, Co, Zn. The processing of microwave digestion, dry ash and the instrument conditions of ICP-MS were studied. Reference materials and the recovery rate of practical samples were analysed to verify the precision and accuracy of this method. The relative recoveries of available nine metals were between 80.0% and 116.5%, and the content of reference materials is consistent with certified values. These results indicated that this method is an accurate analysis.(2) A new method was proposed for determinations of trace zinc, cadmium and copper in food samples.The large surface areas, high chemical reactivity and good adsorption performance make multi-walled carbon nanotubes a coming solid sorbent for preconcentration procedures. Multi-walled carbon nanotubes can serve as solid phase extractor for zinc, cadmium and copper at ultra-trace levels in the presence of alizarin complexone in the present study. Under the best conditions, the calibration of zinc,cadmium and copper were linear in the range of 1.0-100 ug·L-1, 1.0-20 ug·L-1 and0.40-20 ug·L-1, respectively. The maximum adsorption capacity of zinc, cadmium and copper were 2.06 mmol·g-1, 1.00 mmol·g-1 and 0.27 mmol·g-1, respectively. The recoveries of zinc, cadmium and copper spiked in samples were between 80.0% and110.0%. Real water and rice samples were analysed using this method and the results are in agreement with ICP-MS measurements. The concentration of copper can be determined with 5-Br-PADAP as chromogenic agent by the naked eye and the results were similar to which were detected by ICP-MS.(3) A new method for determination of copper in water was established.In the present study, a minicolumn of multi-walled carbon nanotubes with dicyclohexanoneoxaly dihydrazone as metal complexant is proposed for copper determination in water samples by flame atomic absorption spectrometry. Chemical and flow variables such as elution flow rate, solution pH, sorbent capacity, sample flow rate and interference from coexisting ions were investigated. The maximum number of moles of copper ions adsorbed was 1.55 mmol·g-1, the calibration of copper were linear in the range of 2.0-100 μg·L-1. Real water samples spiked with Cu2+ were analysed using this method and the results are in agreement with ICP-MS measurements. |
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