| Research goals:At present, pesticide residues of Organophosphorus,Carbaminate insecticides are used most extensively in our country. In order to know situation of pesticide residues in vegetables in ZIBO central city, we set up GC-MS technique, which is simple,easy and quick to use in laboratory and suited to analyze samples of large number, meanwhile it can test dozens of common Ganophosphorus,Carbaminate insecticides, also we make a wide survey and analysis of situation of pesticide residues in vegetables in Zibo central city.Research methods:1. Sample processing:Weigh accurately 25.00 g in the food processing devices in a processed food samples by adding 50 ml of acetonitrile-acetic acid solution, in the high-speed homogenizer homogenizing 2 min, put in a plug cylinder of 5-7.5 g NaCL, 5g anhydrous sodium acetate, put paved with glass filter paper funnel and filter sample homogenate good. Collection of about 40-50 ml filtrate, covered with cork, severe shock 1 min, at room temperature, put it aside for about 10 min, to acetonitrile phase and water phase layered, accurate drawing 25.00 ml of acetonitrile-phase solution, placed in 50 ml beaker,80℃water bath on a steam heated cup slowly pass into the nitrogen stream blowing, evaporating nearly dry, with acetonitrile transferred to 5ml with Sebi color tube, constant volume with acetonitrile to 2.0ml, to be purified. Weigh 0.1g PSA, 0.3 g anhydrous magnesium sulfate and placed in 5ml sample extracted with Sebi color tube, in the vortex mixer on the mixing 1min, in order to 5000r/min speed centrifuge 1min, the supernatant determined.2. Condition of GC-MS analysis:GC condition:column:RTX-5MS 30m×0.25mm×0.25um; Carrier gas:High-purity helium(Purity99.9999%); Column flow:1.0mL/min; Oven Temperature:;Initial temperature 50℃, hold 1 min, To 30℃/min heating rate to 180℃, hold 1 min, To 15℃/min heating rate to 280℃, hold 10 min; injection mode:Splitless, Open Shunt valve one minute later. Injection volume:11uL; injection port temprature:290℃. MS condition:Ionization mode(EI); Ionization energy:70ev; Quadrupole temperature:150℃. Ion source temperature:230℃; Interface temperature:280℃. Acquisition mode:SIM; Solvent cut time:3.5 min; Tuning mode:auto tuning.3 Range to samples:All 266 samples were randomly collected from Zibo central City, different marketing sites, including supermarkets, wholesale markets and sets trade market. Sampling time for Feberary,2008 year to January,2009, the time spread throughout the year. Adopted by vegetable species, including leafy vegetables, bulb type, melons, vegetables, fruit and vegetables, starchy vegetables and other vegetables.4. Kinds of pesticide residues:Pesticide Type:This type of organic phosphorus(23): Parathion, isofenphos-methy, monocrotophos, parathion-methyl, phosmet, Chlorpyrifos,methamidophos,dichlorvos,acephate,omethoate,phorate, dimethoate fenitrothion, malathion, fenthion, isocarbophos, quinalphos, ethion, demeton, Demeton-methyl, diazinon, iprobenfos, methidathion; carbamate (4):metolcarb, Carbofuran, pirimicarbcarbaryl, Iprobenfos such as 27 kinds of restricted pesticides were detected.5. Content of Quality control:5.1 Quality control of the method:27 kinds of pesticides were drawn standard curve.They were Quantitatied with external standard method.Progressive dilutes the standard series's smallest concentration, sampling analysis,the MDC of 27 kinds of pesticides were obtained. Using standard addition recycling methods to determin the accuracy of this method. Add the high and low concentrations of the standard to prepared samples, Calculate the recovery rate and precision.5.2 The quality control of the investigation results:The standard solution used in the investigation were all certified reference materials. The instruments were all accredited. The environmental conditions met the test requirements. The results can be done to achieve Traceability.Results:1. There are 23 Organophosphorus pesticide,4 Carbaminate insecticides seperated well on specifically chromatographic column, with nice standard curve, value r: 0.9980-0.9996, the lowest testing content:0.0016mg/kg-0.0096 mg/kg, standard impregnant testing precision RSD 6.4%-11.2%, reclaiming rate 76.0%-95.4%.2. This extraction and purification methods, the operation more convenient and simple, solvent consumption of less suitable for vegetables, organic phosphorus and carbamate pesticide residues in a variety of synchronization analysis.3.. From 2008 to 2009, we tested 266 pieces of sample, the result showed that 7.5% of them fall short of national principle.Amongst these samples, disqualification rate of cabbage and" green leaves" is highest.Conclusion:1. The detection methods in this article, pre-treatment process is simple, fast, accurate measurement accuracy, reproducibility, linear range and the minimum detectable levels were suitable for vegetables,23 kinds of organic phosphorus and four kinds of carbamate pesticide residues in Rapid Detection and Analysis.2. The high toxicity of organic phosphorus pesticide in vegetables of ZIBO center city has a higher detection rate, The detection rate and over-limit rate of the leafy vegetables (including cabbage), and bulb type (including stems class) is greater than fruit class (including the root class), the difference was significant (both P<0.05). The pesticide residues of Sales for sale in different places of in vegetables was no significant difference (P>0.10). The pesticide residues detection rate of the second and third quarter, slightly higher than the degree of pesticide detection rate of other quarters (P= 0.0121). Common vegetables and "green sign" of pesticide residues in vegetables, there were significant differences. Exceeded The pesticides which were the largest number of over-limit were methamidophos, omethoate, dichlorvos, and carbofuran. |
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