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Study on Determination of Heavy Metal Elements in Tomato Paste by Inductively Coupled Plasma-Mass Spectrometry

Author: HangYaJuan
Tutor: LiShiYu
School: Xinjiang Agricultural University
Course: Of Food Science
Keywords: inductively coupled plasma-mass spectrometry tomato paste heavy metal food safety
CLC: TS264.2
Type: Master's thesis
Year: 2011
Downloads: 145
Quote: 0
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Abstract


China is the largest exporter of tomato products and processing capacity is the first in the world. The tomato paste yield of Xinjiang region had reached 1,018,300 tons, export inspection was 847,100 tons in 2009, which volued at＄739,000,000. Tomatoes industry occupies a pivotal position in the agricultural economy in Xinjiang.Lead, cadmium, mercury, arsenic, tin, copper and other heavy metals have been food safety inspection item for tomato paste export. Because of seasonal production and constraints of market competition, the inspection of tomato paste for export has some characters that is test time to concentrated and test batch for large, so it’s became the choke point of tomato paste inspection for export. Testing heavy metals in tomato paste by inductively coupled plasma-mass spectrometry was built in the article, it has achieved only once sample preparation and determination of 13 elements interrelated with food safety at the same time. The method was fast and simple, the limits of detection, precision and linear range all can suffice inspection require in food sanitation standard of China and international standard.The main contents of the paper as follow:(1)Pretreatment method of tomato paste sample was established. The methods by electric-hot plate digestion, atmospheric pressure digestion and microwave high pressure digestion were contrasted by experiment, and the parameters of microwave high pressure digestion was determined; the component of digestion reagent is 5mL nitric+1mL hydrogen peroxide. Turbidity determination was used for test solution of digestion, it could provide technical basis for the best digestion procedure establishment.(2) In accordance with the principles of selected nuclides in mass spectrometry, nuclides of 13 kinds of elements were identified by isobaric interference analysis and adduct interference analysis. According to mass range of the analyzed nuclides and investigate results of 19 regions in Xinjiang, internal standard rare earths elements for regulating matrix effect were selected, they are 72Ge,115In and 209Bi. These nuclides make up mixed internal standard solution.(3) Working conditions of ICP-MS instrument were optimized; include RF power, nebulizer flow rate, reaction gas/collision gas flow rate, kinetic energy discrimination and other more than 20 parameters, so that the sensitivity and resolution of instrument attained the best test condition. The pollution elements from gas supply, water, reagent, sample digestion reagent and other aspects were analyzed and evaluated, it provided a basic data for control of reagent blank and sample blank. The effect of eliminating Hg memory interference had been evaluated by test of the water, nitric acid solution and aurum solution.(4) The results of two different ICP-MS determination mode (standard mode and reaction/collision cell mode) on the same tomato paste sample were compared in this study, and the data was treated by T test of statistics. The statistic results showed that two determination modes exist distinct difference when 52Cr, 57Fe,78Se and 118Sn were analyzed, it indicate the method may exists mass interference from adduct ions. The study evaluated also on the effect of eliminating adducts ion interference through different ways.(5) According to 8 heavy metals content of tomato paste in three years in Xinjiang region and national food hygiene standards, the method linear range, the limits of detection for instrument and the limits of detection for method had been confirmed. All test results satisfy requirements of determination for tomato paste export.(6) Through standard addition experiments to sample, the results showed that recoveries of all elements are 83.8%～112.5%, precision RSD are 0.3%～5.0%.(7)The results of method verification test showed the test results accord with the value of reference standard certificate entirely. The standard reference material which was made of tomato leaves have similar sample matrix with tomato paste.

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