A polymeric compound of urushiol Al modified carbon paste electrode was examined for the determination of trace silver in water. In 0 1 mol/L KNO 3 and HAc NaAc solution(pH=5 5), silver is accumulated on the surface o...A polymeric compound of urushiol Al modified carbon paste electrode was examined for the determination of trace silver in water. In 0 1 mol/L KNO 3 and HAc NaAc solution(pH=5 5), silver is accumulated on the surface of the modified carbon paste electrode at -0 1 V( vs .SCE). In the following step, a sensitive oxidation peak of Ag + at 0 22 V could be observed by anodic stripping voltammetry. The peak current is linearly related to the concentration of silver ranged from 4 0×10 -9 mol/L to 2 5×10 -7 mol/L. The detection limit(signal to noise=3) is 1 5×10 -10 mol/L after 20 min accumulation, the average recovery is 100 3%.展开更多
Tea is one of the most popular beverages, consumed by over two thirds of the world’s population; but the aluminum accumulation property of tea plant is becoming the focus of many researches because of aluminum’s kn...Tea is one of the most popular beverages, consumed by over two thirds of the world’s population; but the aluminum accumulation property of tea plant is becoming the focus of many researches because of aluminum’s known adverse effect on human health. Investigation of the interactions of catechins with Al3+ showed that during the interaction of catechins with Al3+, the UV-vis spectrum of catechins was changed. Absorption of EGCG at 274 nm decreased and increased at 322 nm; EC and C’s at 278 nm changed little. The ratio of Al3+ to EGCG was 1:1 in pH 5.0 buffer solution; in pH 6.2 buffer solution, the ratio in the Al-EGCG complex was 1:1. Interestingly, while the ratio reached to over 2, after the complex of Al-EGCG started polymerization, the ratio in the polymer was 2:1. In pH 6.2 buffer solution, the complex behavior of C with Al3+ was the same as that of EGCG, with a little difference for EC. When the ratio of Al3+ to EC was <1, the complex in ratio was 1:2, but, the complex polymerized when the ratio of Al3+ to EC was >1. It was found that the ratio of Al3+ to EC in the polymer was 1:1. Polymerization of Al-catechin complexes might reduce aluminum absorption in the intestine. Kow value was also employed to study the properties of aluminum species in tea infusion (at gastric and intestine pH condition) and the effect of catechins and tea polyphenols on Kow in buffer solution. Results showed that Kow value rose much higher at the intestine pH than at the gastric pH. Tea polyphenols and catechins could greatly reduce aluminum Kow value in acetic buffer, indicating that these compounds may reduce aluminum absorption during tea intake.展开更多
文摘A polymeric compound of urushiol Al modified carbon paste electrode was examined for the determination of trace silver in water. In 0 1 mol/L KNO 3 and HAc NaAc solution(pH=5 5), silver is accumulated on the surface of the modified carbon paste electrode at -0 1 V( vs .SCE). In the following step, a sensitive oxidation peak of Ag + at 0 22 V could be observed by anodic stripping voltammetry. The peak current is linearly related to the concentration of silver ranged from 4 0×10 -9 mol/L to 2 5×10 -7 mol/L. The detection limit(signal to noise=3) is 1 5×10 -10 mol/L after 20 min accumulation, the average recovery is 100 3%.
文摘Tea is one of the most popular beverages, consumed by over two thirds of the world’s population; but the aluminum accumulation property of tea plant is becoming the focus of many researches because of aluminum’s known adverse effect on human health. Investigation of the interactions of catechins with Al3+ showed that during the interaction of catechins with Al3+, the UV-vis spectrum of catechins was changed. Absorption of EGCG at 274 nm decreased and increased at 322 nm; EC and C’s at 278 nm changed little. The ratio of Al3+ to EGCG was 1:1 in pH 5.0 buffer solution; in pH 6.2 buffer solution, the ratio in the Al-EGCG complex was 1:1. Interestingly, while the ratio reached to over 2, after the complex of Al-EGCG started polymerization, the ratio in the polymer was 2:1. In pH 6.2 buffer solution, the complex behavior of C with Al3+ was the same as that of EGCG, with a little difference for EC. When the ratio of Al3+ to EC was <1, the complex in ratio was 1:2, but, the complex polymerized when the ratio of Al3+ to EC was >1. It was found that the ratio of Al3+ to EC in the polymer was 1:1. Polymerization of Al-catechin complexes might reduce aluminum absorption in the intestine. Kow value was also employed to study the properties of aluminum species in tea infusion (at gastric and intestine pH condition) and the effect of catechins and tea polyphenols on Kow in buffer solution. Results showed that Kow value rose much higher at the intestine pH than at the gastric pH. Tea polyphenols and catechins could greatly reduce aluminum Kow value in acetic buffer, indicating that these compounds may reduce aluminum absorption during tea intake.
