Electrochemical Monitoring of Methylparathion Degradation in an Acid Aqueous Medium in Presence of Cu(II)

Abstract

A study was undertaken to determine the effect of Cu(II) in degradation of methylparathion (o,o-dimethyl o, 4-nitrophenyl phosphoriotioate) in acid medium. Initial electrochemical characterization of Cu(II) and methylparathion was done in an aqueous medium at a pH range of 2–7. Cu(II) was studied in the presence of different anions and it was observed that its electroactivity depends on pH and is independent of the anion used. Methylparathion had two reduction signals at pH ≤ 6 and only one at pH > 6. The pesticide's transformation kinetic was then studied in the presence of Cu(II) in acid buffered aqueous medium at pH values of 2, 4, and 7. Paranitrophenol appeared as the only electroactive product at all three pH values. The reaction was first order and had k values of 5.2 × 10^?3 s^?1 at pH 2, 5.5 × 10^?3 s^?1 at pH 4 and 9.0 × 10^?3 s^?1 at pH 7. It is concluded that the principal degradation pathway of methylparathion in acid medium is a Cu(II) catalyzed hydrolysis reaction.     

示波极谱法测定地面水中的钒

应用钒（ Ｖ） ５ Ｂｒ Ｐ Ａ Ｄ Ａ Ｐ Ｈ２ Ｏ２ 体 系产生的 络合极 谱波对地 面水中 的钒 进行 了测 定，并 讨论了测试 条件。钒 浓度在 ００１ ～２２５ μｇ／２５ ｍ Ｌ 范围 内极谱 电流与钒 含量呈线 性关系 ，本法具有 较高的选择 性和灵 敏度，测定 地面水 中的钒结 果令人 满意     

Quantification of metallothionein in whole body gammarus locusta (crustacea: amphipoda) using differential pulse polarography

A polarographic method was optimised for the quantitative determination of metallothionein (MT) in whole body Gammarus locusta (Crustacea: Amphipoda). The identity of the MT-like proteins was examined using electrophoretic analysis (SDS-PAGE) and induction studies (water-borne exposures to copper). The MT-method was then used to examine changes in MT levels over the lifetime (juveniles, sub-adults and adults) of a laboratory population of G. locusta; copper (Cu) and zinc (Zn) body burden were also measured by flame atomic absorption spectrometry. MT was quantified by heat-denaturation of 30?000?g supernatants (to remove the bulk of non-MT proteins) followed by differential pulse polarography (DPP) to measure sulphydryl-group containing proteins. DPP proved to be a sensitive and reliable method to quantify heat-stable total sulphydryl-proteins. The majority of the latter was indicated to be MT from SDS-PAGE and induction studies. SDS-PAGE revealed a putative MT of 23?±?0.6?kDa app. mol. wt., consistent with the average size of dimeric MTs (10–20?kDa) found in several aquatic invertebrate species. Copper-exposure revealed parallel increases in the amounts of 23?kDa protein and total sulphydryl-proteins. Levels of whole body MT (rabbit pure MT as standard) range between 1.3 and 2.3?mg?g^?1 dry wt. over the lifetime of G. locusta. Sex-related changes in MT status were observed, the levels in females being 1.6 times higher than in males (p<0.05). Copper and Zn body content changed over the lifetime of G. locusta, the levels in juveniles (p>0.05) and sub-adults (p<0.05) being higher than in adults. It is concluded that the inclusion of MT in ecotoxicological studies with amphipod crustaceans require some caution with respect to the stages of moulting and/or sexual maturation of organisms, but this should not provide any major impediment in its use in metal pollution monitoring.     

Polarographic investigations on the complexation of cadmium and zinc by thiol peptides

Complex formation of Cd²⁺ and Zn²⁺ with thiol derivatives has been investigated by differential pulse polarography. The binding of Cd²⁺ and Zn²⁺ with cysteine (CySH), glutathione (GSH) and the model peptide N‐acetyl‐cysteine‐methylamide (ASH) reveals different stoichiometry. Thus, Cd²⁺ forms 1:1 and 1:2 complexes with CySH while 1:2 and 1:4 complexes have been observed with GSH and ASH, respectively. Overall formation constants of Cd²⁺ with CySH (Iogβ ₂ 15.3) and with GSH (Iogβ5₂ 14.4) have been estimated using competitive complexation with nitrilotriacetic acid (NTA). Investigation of competition between Zn²⁺ and Cd²⁺ for the thiol complexation has underlined the role played by the amino group in CySH for the stabilization of Zn complexes in contrary to Cd complexes.     

碱性消解-伏安极谱法测定土壤中六价铬

分析了汞滴尺寸、支持电介质等因素对碱性消解-伏安极谱法测定土壤中六价铬的影响。在优化实验条件下,该方法检出限为7.65μg/L,相对标准偏差(n=7)为4.6%。以2个样品为例,每个浓度进行6次平行测定,加入六价铬浓度为10μg/L,六价铬的回收率为91.4%~120%,RSD≤5%。与二苯碳酰二肼分光光度法进行比较,2种方法测定值基本一致。     

Photochemical degradation of methylparathion in the presence of humic acid

Photochemical degradation of methylparathion (O,O,-dimethyl O-4 nitrophenylphosphorothioate) in the presence of humic acid between pH 2 and 7 was monitored by differential pulse polarography. Humic acid was not electro-active under the experimental conditions used in this study. Only the pesticide and its main degradation product at pH 2 exhibited polarographic signals. Photolysis of methylparathion in acid media was sensitized by humic acid since the pesticide did not degrade in the absence of this compound. Methylparathion degradation in the presence of humic acid was observed at each of the studied pHs. The reaction was first-order with rate constant values ranging from 2 × 10^?3 to 6.3 × 10^?3 min^?1.     

痕量亚硝酸根的极谱测定

在酸性介质中,次甲基蓝与亚硝酸根发生亚硝化反应,本文选用0.08mol/l的盐酸,其亚硝化产物在—0.65V(us.SCE)附近产生一灵敏的极谱波,亚硝酸根浓度在0.002—0.24ug/ml范围内与二次导数波高成直线关系,本法用于水样和蔬菜中亚硝酸根的测定,选择性好,灵敏度较     

活动态铊的极谱法测定

文章研究了活动态铊的提取条件和极谱测定方法,并用此法测定了多个沉灰渣样品中活动态铊的含量。     

示波极谱测定空气中甲醛含量的方法及其应用

本文研究了用示波极谱测定室内空气中甲醛含量的方法，其结果为：本法测定甲醛的检测下限为３４μｇ／Ｌ，加标回收率为８７５～１１００％，变异系数为４２５～８６３％，该法灵敏度高，甲醛含量与极谱峰高的线性关系好，是一种可靠的测定室内空气中甲醛含量的方法。同时还研究了缓冲液的ｐＨ值及吸收液放置时间对甲醛测定结果的影响，并将该法应用于评价空气净化器去除室内空气中甲醛的效果。     

不除氧单扫描示波极谱法测定茶叶中钙

研究了在不除氧条件下，用单扫描示波极谱法测定茶叶中钙，在０．０２ｍｏｌ／Ｌ ＫＯＨ体系中，钙－桑色素络合物于－０．７８Ｖ产生一灵敏的极谱峰，峰电流与钙浓度在０．１￣０．８μｇ／ｍＬ之间有良好的线性关系。方法灵敏、准确、简便、选择性好。