Flow Injection Chemiluminescence Determination Of Lead And Chromium, Food Additives Calcium Propionate

In this paper, the determinations of trace lead and chromium in calcium propionate synthesized from egg shell which acts as the food additives by using Flow injection chemiluminescence (FI-CL) are realized based on the literatures.Lead(II) sensitizes the weak CL induced by the oxidation of luminol with hydrogen peroxide in presence of 1,10-phenanthroline. A linear relationship between CL intensity and the lead(II) concentration existed. However, the CL system is unstable and the determination precision is poor. In this work, surfactant Tween-20 was introduced in the above-mentioned CL system. The obtained results showed that the system was more stable and the sensitivity was improved. Additionally the system was enhanced and the detection precision was good in the presence of Tween-20. Furthermore, the introducing of Tween-20 broadened the pH from 3 to 3~8 for the determination of lead(II), which facilitated the detection. Trace lead(II) was separated from the matrix and adsorbed by 717-strong basic chloric type anion-exchange resin, while plenty of calcium and magnesium cations co-existed in sample were not adsorbed by the resin. Satisfactory results were obtained when using the above-mentioned detection methodology for the determination of lead( II) elutedfrom the resin.In present work, the determinations of trace chromium(III) andchromium(VI) are realized based on the hydrogen peroxide-luminol CL emission enhanced by chromium(III). Chromium(VI) was separated from the matrix and adsorbed by 717-strong basic chloric type anion-exchange resin, then the adsorbed chromium(VI) was eluted from the resin and reduced to chromium(III) by hydrogen peroxide in acidic solution at the same time. Chromium(III) was determined by the hydrogen peroxide-luminol CL mentioned above. By this way, the content of chromium(VI) was obtained. Since the co-exiting calcium and magnesium cations in the sample would interfere with the direct determination of chromium(III) and chromium(III) wasnot adsorbed by the resin and flowed with the eluted solution, chromium(III) was oxidized to chromium(VI) by ammonium peroxydisulfate solution. According to the separating and determination procedure mentioned above, the result of chromium(III) determination was obtained. In general, chromium(VI) which adsorbed on the resin was eluted by ascorbic acid or sodium bisulfite solution, however, the residue of ascorbic acid or sodium bisulfite disturbed the CL analysis of chromium. In this work, acidic hydrogen peroxide was used as the elution solution and the reducer, and the obtained results showed that it did its work well. In addition, the determination was free from the interferences induced by other ions in the elution solution since the excessive hydrogen peroxide decomposed to water and oxygen by heating.Zhu Fen-xia(Analytical Chemistry) Directed by Prof. Yang De-yu...