Separation And Preconcentrati On Of Pb, Cd,Cr And In In Food And Waste By Using With The Combination Coprecipitation-Flame Atomic Absorption Spectrometric Determination

As we all know,people’s safety awareness of environment and food have improved with the social development and progress.Thus,more and more measuring methods and apparatus have been invented in order to solve problems we have met. For example,flame atomic absorption spectrometry (FAAS) is a widely used technique for the determination of trace metal ions due to its easy usage,low cost and selectivity.Determinations of trace metal ions using FAAS are difficult because of lower levels of analyte ions than the detection limits of FAAS.Inductively coupled plasma optical emission spectrometry(ICP-AES) can solve problem mentioned above,but it’s too expensive to afford it.In order to solve these problems,the separation and preconcentration method of coprecipitation has been used because of its simplicity, short analysis time and high preconcentration factor.Bi(Ⅲ),Al(Ⅲ) and Ba(Ⅱ) were used as carriers which chelated with 1-(2-pyridylazo)-2-naphthol for the first time to detect the content of trace lead,cadmium,chromium and indium in food and waste samples by flame atomic absorption spectrometry(FAAS).The optimum coprecipitation of these new methods including amount of reagent,quantity of carrier,pH,the standing time of the precipitate and sample volume had been confirmed for the quantitative recoveries of the analytes.The interference of co-existing ions,sensitivity,precision and detection limit of the methods were also evaluated.Meanwhile,the mechanism has been discussed to deepen our understanding of coprecipitation.This paper focus on the following four systems to separation and preconcentra-tion of heavy metal ions:1.Bismuth(Ⅲ) was used as a carrier which chelated with PAN to detect the content of trace Pb.The sensitivity and the relative standard deviation(RSD) were found 0.0143(mg/L)-1,1.31%,respectively.The optimum procedure allows the deter-mination of lead with limit of detection of 16.3μg/L.The mechanism of coprecipitation of trace Pb on Bi(Ⅲ)-PAN was studied by adding Pb before and after precipitation.Both of these two procedures were surface adsorption.2.Bismuth(Ⅲ) was also used as a carrier which chelated with PAN to detect cadmium.The sensitivity,the detection limit and the RSD of this method were found 0.1528(mg/L)-1,3.40μg/L and 0.16%,respectively.The mechanism of this system was studied,similarly.One part of Cd cling to Bi(Ⅲ)-PAN,the other part of Cd formed mixed crystal when adding Cd before precipitation.Meanwhile,most of Cd was absorbed on chelate when put cadmium in solution after precipitation.3.Aluminum(Ⅲ) was used as a carrier which chelated with PAN to detect the concentration of Cr(total).The sensitivity and the detection limit of the method were 0.0461(mg/L)-1 and 8.98μg/L.Both of two different procedures were surface adsorption.4. Barium(Ⅱ) was used as a carrier which chelated with PAN to detect trace Pb indium in used mercury-free battery.The sensitivity,the detection limit and the RSD of this method were found 0.0147(mg/L)-1,20.4μg/L and 0.79%,respectively.The mechanism of coprecipitation of trace In on Ba(Ⅱ)-PAN was also discussed by adding In before and after precipitation process.Both of them were formed adsorption.