Determination Methods Of Six Heavy Metals In Fruits And Vegetables

Nowadays, food safety issues have becoming increasingly prominent, especially heavy metal pollution has gone deep into the fruits and vegetables, and it has becoming a potential threat to human health. The first part of the work is mainly aimed at establishing a fast and efficient method to determinate simultaneously the concentration of six higher levels heavy metals Cu, Pb, Ni, Cr, Cd and Co of fruits and vegetables.Because some low levels of heavy metals can not be a measured accurately and directly, using an appropriate pre-separation and enrichment means is necessary. Cloud point extraction is an environment-friendly analysis method for enrichment which uses a non-ionic surfactant as a extraction agent instead of a volatile organic solvent. Dual-cloud point extraction (d-CPE) is based on the traditional cloud point extraction however joined an anti-extraction process, it not only ruled out the interference of the first step in cloud point extraction process coming from the other macromolecules entered the surfactant phase, while eliminating the risk that the high concentration of macromolecules wrapped in the surfactant may clog pipeline of ICP-AES. The details of work are as follows.Eight kinds of fruits and vegetables (nine kinds of sample) as the research objects, using wet digestion, a method of simultaneous detection of six heavy elements the concentration of Cu, Pb, Ni, Cr, Cd, Co using ICP-AES was established. Under optimal conditions, the experimental results showed that:The detection limits of Cu, Pb, Ni, Cr, Cd and Co were0.0015μg·mL-1,0.024μg·mL-1,0.0042μg·mL-1,0.0033μg·mL-1,0.0006μg·mL-1and0.0021μg·mL-1. Relative standard deviation is between0.12%and10.29%, recoveries ranged from89.4%to108.6%(The recovery of Ni in potatoes is123.7%). According to the national food hygiene standards in the fruit and vegetable standards, the results showed that Pollution is more serious of the two heavy metal elements Cr, Cd, causing a potential threat to the physical health of the residents.A new method is developed for the simultaneous determination of Cu, Pb, Ni, Cr, Cd and Co by ICP-AES associated with Dual cloud point extraction. The complexing agent is Diphenyl sulfide azo carbonyl hydrazide (dithizone), and Trition X-114was added as a nonionic surfactant. The complex of the mixed metal ions with dithizone was extracted into the surface active agent, and using the dilute HNO3stripping it into the inorganic phase, and then detecting by ICP-AES. The effects of experimental conditions such as pH, concentration of pH, chelating agent and surfactant, equilibration temperature and time on extraction rate of dual-cloud point extraction was studied. Under the optimum conditions, the detection limits of Cu, Pb, Ni, Cr, Cd and Co were0.0011μg·mL-1,0.0042μg·mL-1,0.0013μg·mL-1,0.0004μg·mL-1,0.0005μg·mL-1and0.0004μg·mL-1, the enrichment factor ranged from10.23to22.71, relative standard deviation is between3.97%and5.65%, recoveries ranged from92.1%to104.6%. In this method, the extraction rate of Pb exceeds90%, extraction rates of Cu and Co are more than80%, extraction rates of Ni, Cr and Cd are all about50%, extraction of Cu, Pb and Co is better.