Analysis Of Metal And Organic Compound Residues In Edible Vegetable Oils To Influence Product Quality Or Edible Safety

During the process of planting, producing, transporting or storing, some compounds like antioxidants or organic solvents might be added to the edible vegetable oils. At the same time, the oils could be polluted by organic pesticides or heavy metals as well. Thus the safety issue causes wide spread concem among people. It is important to establish and perfect the determination standard for food safety. In this thesis, new methods have been developed to determine the concentration of metal elements or organic compounds residues which affect the quality or safety of edible vegetable oils with satisfactory results. The research results contribute to the drafting of detection standard and to the simultaneous determination of multi-residues in the field of food safety. The main results are as follows:1. A simple, quick and nontoxic analytical method for the simultaneous determination of five synthetic antioxidants [t-butyl-4-hydroxyanisole (BHA), 2, 6-di-t-butylhydroxytoluene (BHT), t-butyl hydroquinone (TBHQ), ethoxyquin (EQ) and 2, 6-di-tert-butyl-4-hydroxymethylphenol (Ionox 100)] in edible vegetable oil has been developed. The analytes were extracted by ethanol, then separated and detected by GC-MS. Extraction conditions such as volume of ethanol, mixing time and number of extractions were investigated and optimized by an orthogonal array experimental design. The five compounds behaved linearly in the 0. 1-20. 0 mg/L concentration range, and the limits of detection (LOD) for BHA, BHT, TBHQ, EQ and Ionox-100 were 1. 00, 0. 92, 11. 5, 0. 83 and 1. 39μg/L, respectively. The recoveries at the tested concentrations of 1. 00, 20. 0 and 100 mg/kg were 75. 6-123%, with coefficients of variation below 10. 0%. The proposed procedure was successfully appliedto the simultaneous analysis of the five antioxidants in soybean oil, tea oil, edible blended oil, rap oil, peanut oil, -peanut blended oil, and sesame oil samples purchased from local supermarkets.2. A simple, accurate and sensitive method for the simultaneous analysis of eleven trace elements (Fe, Cu, Co, Ni, Pb, A1, Zn, Cd, Cr, Mn and Mg) in vegetable oils by ICP-AES has been developed. The oils were digested by H₂SO₄ ash method. The method detection limits (MDLs) of the eleven elements were in the range of 0. 1-3. 6μg/kg. The average recoveries at three concentrations of 0. 1mg/kg, 0. 5mg/kg and 1 mg/kg were between 70. 4% and 113% with the RSD in the range of 1. 01%-10. 6%. The proposed method has been applied to the determination of above elements in soy, peanut, sesame, rap, tea, refined oil and blended oils with satisfactory results.3. A simple and accurate method for the determination of phosphatide in vegetable oils by ICP-AES has been developed. The spectrum interferences of P213. 617 nm and P214. 914 nm caused by copper were corrected by multi-component spectral fitting (MSF). The sample preparation methods were studied. The experimental results showed that the analytical results of microwave digestion and active carbon ash digestion are all in accordance with that of Chinese national standard phosphomolybdate blue spectrophotomety. The MDL of active carbon ash digestion was 0. 053 mg/kg, which was. lower than that of microwave digestion (0. 42 mg/kg). So for the detection of low concentration phosphatide, the accuracy and precision of active carbon ash digestion were better than that of microwave digestion. The proposed method has been applied to the determination of phosphatide in rap oil, tea oil, peanut oil, soybean oil, edible blended oil, peanut blended oil and corn embryo oil samples with satisfactory results.4. A simple and sensitive method for the determination of glyphosate (Gly) and its metabolite aminomethylphosphonic acid (AMPA) in edible vegetable oils has been proposed. The extractions by water were cleaned up with ENVI-18 solid phase extraction column, then separated and detected by ion chromatography with integrated pulsed amperometric detection (IPAD). The average recoveries at three concentrations of 0. 01 mg/kg, 0. 05 mg/kg and 0. 10 mg/kg were between 93. 9% and 114% with the RSD in the range of 1. 76%-4. 84%. The method detection limits (MDLs) of Gly and AMPA were 1. 0μg/kg, 0. 5μg/kg respectively. The proposed method has been applied to the determination of Gly and AMPA in cottonseed oil, soybean oils, peanut oil, and rap oils with satisfactory results.5. The separation behaviors of organochlorine pesticides, organophosphorus pesticides, carbmate pesticides and pyrethriod pesticides and oil matrixes were systematically investigated with gel permeation chromatography (GPC) for its outstanding capability of moving lipid. A method was proposed for the quantitative simultaneous determination of 29 pesticides in edible vegetable oils by GPC and GC-MS. The average recoveries at three concentrations of 0.05 mg/kg, 0.10 mg/kg and 0.20 mg/kg were between 82.0% and 119% with the RSD in the range of 1.35%-10.2%. The method detection limits (MDLs) of the 29 pesticides were in the range of 0.X-Xμg/L. The method could meet the requirement of analysis of actual samples.