Study On The Determination Of Heavy Metal And Organotin Pesticide Residues In Food

In recent years, as environmental pollution is increasing, more and more people pay attention to the food safety. The pollution of heavy metals and organic pesticides residues is one of the main aspect of food security, therefore the establishment of new analysis methods of heavy metals and organic pesticides residues in food is of great importance for the construction and improvement of the food safety standards. Base on the extensive literatures, using modern separation and analysis techniques, the determination of the heavy metals and organotin pesticides residues in honey, lindera aggregate, tea, scallop and pear were carried out with satisfactory results. The main results are summarized as follows:1. A simple and accurate method for the simultaneous analysis of 20 metal elements (Na, K, Mg, Ca, Sr, Ba, Mn, Fe, Cu, Zn, Al, Se, Ni, Li, V, Cr, Co, Cd, As and Bi) in honey by ICP-AES has been developed. The honey was dissolved in concentrated HNO3 directly, then diluted by water before it was detected by ICP-AES. The averaged recoveris of the 20 elements were between 75.2%-110% and the RSDs were lower than7.00%. The limits of detection were between 0.0038～0.29 mg/kg. The method was applied to the simultaneous determination of 20 elements in six kinds of honey (wild honey,osmanthus honey,guan shengyuan honeys,chinese milk vetch honey,acacia honey and wang's honey) with satisfactory results. The results showed that the honey is an excellent source of K, Mg, Ca, Se, Fe, Zn, Al and other trace elements. The contents of trace elements in different kinds of honey are different. The contents of harmful metales are lower than the limitation standards of harmful heavy metals in food. Cd, As, Bi were not detected in the six samples.2. A method for the simultaneous determination of 21 elements (Al, B, Ba, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Ni, P, Pb, V, Zn, Be, Cd, Sr and Na) in Lindera aggregata and its first and second decoctions by ICP-AES was developed. The Lindera aggergata was digested with HNO3-H2O2 by microwave, the first and second decoctions were digested directly on electric hot plate. The average recovies were between 82.0% and 115% with the RSD(n=5) below 10%. The limits of detection were between 0.3 ug/L and 12.9 ug/L. The experimental results showed that there are rich K, Ca in Lindera aggregata and the content of Mg, Al, Fe, Mn are also relatively abundant, moreover it was also found that the dissolved rates of the 21 elements are different from each other. The experimental results would provide scientific basis to further explore the relativity of element content and curative effect, at the same time it would also guide the rational use of Lindera aggregata.3. A method for the determination of Li, Be, B, Sc, Ti, V, Cr, Co, Ni, Cu, As, Sr, Mo, Cd, Sn, Sb, La, Hg, Tl, Pb and Bi in animal and plant samples by ICP-MS was developed. Microwave digestion conditions has been studied.72Ge, 115In,197Au were used as on-line mixed internal standard to correct matrix interference and instrument drift, ICP-MS's operating conditions have been optimized and the mathematical equations were used to eliminate the mass interference. The detection limits were between 0.01 ng/L and 14.32 ng/L and the RSDs were lower than 9.00%. The method has been validated by standard materials of tea (GBW07605) and scallops (GBW10024) with satisfactory results. The method is simple, rapid and high sensitivity, it was suitable for the annlysis of trace elements in animal and plant samples.4. A method was developed for the determination of As in standard materials of Scallop and Tea by ICP-MS. After the microwave digestion, the samples were directly determined by ICP-MS with normal mode and collision reaction interface(CRI) mode,72Ge was used as on-line internal standard to correct the matrix interference and the instrument's drift. The difference between the two analysis mode was compared, the accuracy and the detection limit of CRI mode were more superior than that of normal mode. The detection limits of the normal mode and CRI mode were 40.1 ng/L and 1.6 ng/L, respectively, the RSDs were between 1.1% and 5.8%. In addition, signals of As in different concentration solution of NaCl were determined to discuss the effect of the removal of 40Ar35Cl+ by CRI mode, the experimental results showed that CRI technique is fit for the analysis of As in complex matric samples for its good behavior in elimination of the interference caused by 40Ar35Cl+.5. A method for the determination of fentinhy droxide and azocyclotin in pear by HPLC-ICP-MS was developed, The pesticides were shaking extracted by acetone-ethanoic acid (99:1,v/v) and hexane, then the extract was cleaned up with a silica solid phase extraction column. Under the optimized experimental conditions, the determination of pesticides in the final extracts was carried out by HPLC-ICP-MS. The two compounds behaved linearly in the 0.5-50μg/L concentration range and the correlation coefficients was 0.9990 and 0.9999. The limits of detection (LOD) for fentinhy droxide and azocyclotin were 0.25μg/L and 0.47μg/L, respectively. The recoveries at the tested concentrations of 10,50 and 100ng/g were 83.0%～109%, with coefficients of variation between 1.5% and 6.5%. The proposed procedure was successfully applied to the determination of fentinhy droxide and azocyclotin in pear.