Research And Application Of The Method For Determination Of Heavy Metals In Vegetables

Vegetables are common food in people's daily life,it can provide essential vitamins,minerals and dietary fiber for human body.With the continuous improvement of people's living standard,people are more and more inclined to buy pollution-free green vegetables.However,in recent years,the survey data show that many cities in the surrounding suburbs of China are suffering from different levels of soil pollution.Even in the metropolises of China,the lead,cadmium,chromium,arsenic and other heavy metals in vegetables,fruits and food crops already approximate or exceed the national standard value.Therefore,enhancing the quality and safety control of vegetable production and circulation is the top priority.In view of the above situation,the contents of copper,lead,cadmium and chromium in vegetables were determined by flame and graphite furnace atomic absorption spectrometry while the content of arsenic was determined by atomic fluorescence spectrometry.Then,these two methods were studied and evaluated.The dry-ash method and three wet digestion methods,as traditional electric hot plate digestion acid,automatic graphite digestion and full automatic microwave digestion are experimentally compared.The limit of detection,precision and accuracy of graphite furnace atomic absorption spectrometry for determination of lead,cadmium,chromium in vegetables were studied and compared by determination of composition analysis of standard substances.The contrast test of the purity of ultra pure water and nitric acid,ammonium nitrate and ammonium phosphate,concentration of ammonium phosphate and the volume of fixed capacity on the machine which were used in the graphite furnace method for the determination of cadmium were carried out as well.For atomic fluorescence spectrophotometry determination of arsenic,determine the optimal photomultiplier negative high voltage,lamp current,carrier gas flow rate and thiourea ascorbic acid concentration.After then,the best experimental scheme was obtained by optimizing of experiment parameters.Then,this best scheme was applied in a real case.10 kinds of vegetables were collected in the large supermarket and the farmer's market in Xi'ning region of Qinghai province.Then,according to the analysis results of our best experiment scheme,the current status of heavy-metal pollution in vegetables in Xi'ning area is carried out.This will bring some efficient insight for vegetable quality supervision for the access to the marketin the future.For now,this optimal scheme was already utilized in the evaluation of vegetables in Xi'ning region,which will be of help for the local food safety.