微量元素与脂代谢

铬是人体内必需的微量元素．综述了缺铬对脂代谢的影响、补铬对脂代谢的效应和铬对脂代谢作用的机制．根据动物实验和人群研究调查，阐述了铬与脂代谢有关，且补充铬对胆固醇和某些脂蛋白含量都有良好的作用．指出了铬可能与胰岛素及铬对脂代谢中关键酶的作用密切相关．但是,有关的作用机制仍未充分阐明。有必要进一步研究。     

铬鞣液组成的研究方法进展

研究铬鞣液的组成及各种铬配合物在铬鞣过程所起的作用,对于阐明铬鞣机理和实际的铬鞣操作过程有重要的指导意义。对国内外研究铬鞣液组成所采用的主要的研究方法及其研究成果加以总结归纳,并对各种方法的特点作简要评述。     

稀土元素对铬酵母中铬含量影响的研究

研究了稀土化合物在铬酵母制备过程中对总铬和有机铬含量的影响作用。镧、铈、镨、钕等轻稀土化合物均能明显提高铬酵母中总铬和有机铬的含量 ,其中镧化合物对铬酵母中总铬和有机铬含量的提高作用最显著 ,总铬含量可达到 70 8.33μg·g- 1 ,有机铬含量可达到 6 39.0μg·g- 1 ,是未加稀土铬酵母样品的近 3倍 ;添加钕化合物的铬酵母中有机铬占总铬的比例最高 ,可达到 97.5 %。通过紫外光谱分析 ,发现有机铬在 2 6 0nm处有特征吸收峰 ,通过红外光谱分析 ,发现有机铬在 478cm- 1 处有特征吸收峰 ,而加稀土化合物的铬酵母样品在此两处的吸收峰值均高于未加稀土的铬酵母样品     

催化动力学光度法测定水中痕量铬——应用β-环糊精作增敏剂

医学研究发现，六价铬有致癌的危险。电镀、制革、制铬酸盐或铬酐等工业废水，均可污染水源，使水中含有铬。因此研究铬，特别是环境及人体中铬的测定方法，是十分有意义的。近年来有许多关于催化动力学光度法测铬的报道。试验发现：在环糊精存在下，过氧化氢氧化罗丹明B的褪色反应，铬具有明显的催化作用，据此建立了测定铬的方法。该方法用于水中痕量铬的测定。     

具有切割DNA活性的铬配合物*

铬配合物切割DNA的活性在医学、药学及生物学领域引起了广泛关注。本文综述了具有切割DNA活性的铬配合物的研究进展,介绍了不同价态铬的多种配位模式配合物切割DNA的活性,总结了铬配合物切割DNA的作用机理,展望了不同价态铬配合物的研究和发展方向。     

60例非胰岛素依赖型糖尿病人发铬分析

用ＤＣＴ直读光谱仪测定了６０例非胰岛素依赖型糖尿病人发铬微量元素。铬（Ⅲ）含量低于对照组。具有生物活性的铬（Ⅲ）有机化合物－葡萄糖耐受因子（ＧＴＦ）是胰岛素的“协同激素”。铬（Ⅲ）含量降低，葡萄糖耐量受损，可导致胰岛素作用降低，影响糖元的合成与代谢。提示铬的测定对非胰岛素依赖型糖尿病早期诊断及治疗有一定的临床价值。     

与铬鞣有关的胶原化学研究进展

本文在回顾与制革有关的生皮胶原结构的基础上, 概述了铬鞣过程胶原与铬(?) 之间的作用, 并对近年来利用胶原计算机模型探讨鞣制反应和以提高铬鞣有效性为目的的胶原修饰化学的研究状况及其发展前景作简要论述。     

牛血清白蛋白与铬天青S作用机理的研究

用三种不同方法相互对照,求出了铬天青S与牛血清白蛋白的结合常数和结合个数,提出了蛋白质等电点前后或不同铬天青S浓度下,两者存在不同的结合模式。利用Forster非辐射能量转移理论确定了铬天青S在牛血清白蛋白上的结合位置,利用铬天青S对BSA的荧光猝灭,对两者的作用机理作了初步探讨。     

蛋白质与酸性铬蓝K相互作用的分光光度研究

本文研究了不同酸度下, 酸性铬蓝K与牛血清白蛋白的作用情况。用光度法求出了不同条件下酸性铬蓝K与牛血清白蛋白的结合个数或结合常数, 并用三种不同的方法相互进行对照。证明酸性铬蓝K在牛血清白蛋白上有两类不同结合部位。     

过渡金属氨基酸席夫碱配合物的合成

合成了6个过渡金属氨基酸席夫碱配合物——L-酪氨酸缩水杨醛合铬(钼),L-赖氨酸缩水杨醛合铬(钼),DL-α-丙氨酸缩水杨醛合铬(钼),其结构经UV,IR和元素分析表征。UV测定结果表明,配合物均可与DNA发生插入作用。     

Separation of Cr(III) and Cr(VI) using melamine-formaldehyde resin and determination of both species in water by FAAS

A method is described for the determination of Cr(VI) and total chromium by FAAS. Cr(VI) is separated from Cr(III) by adsorption on melamine-formaldehyde resin. After elution of Cr(VI) with 0.1 mol/l NaAc solution, it is analysed by FAAS. Total chromium is determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with hydrogen peroxide, total Cr(VI) is concentrated as above. If the total concentration of chromium is sufficient, the determination can be directly made by FAAS. Cr(III) can then be calculated by subtracting Cr(VI) from the total Cr. This method was successfully applied to the determination of chromium in lake water.     

Speciation dependent studies on chromium absorption using calcium alginate and iron doped calcium alginate biopolymer

Attempt has been made to develop methodologies for preconcentration of chromium in the biodegradable polymer beads. The uptake behaviors for chromium have been studied with Ca-alginate (CA) and Fe-doped calcium alginate (Fe-CA) beads. The work also aims to study the differential attitude of CA and Fe-CA towards Cr(III) and Cr(VI) so that, depending on the oxidation state of chromium effluent, environmentally sustainable methodologies can be prescribed for removal of chromium. Radiotracer ⁵¹Cr has been chosen as precursor of stable chromium throughout the experiment. It was found that Fe-CA beads are suitable for removal of Cr(III) and Cr(VI) while CA beads can be used for the speciation and separation of Cr(III) and Cr(VI) at pH 5.     

Gas Chromatographic Determination of Trace Amount of Chromium

Trace amount of chromium was first converted quantitatively to volatile chromium chelates such as chromium(III) acetylacetonate, Cr(acac)₁, chromium(III) trifluoracetylacetonate, Cr(tfa)₃, and chromium(III) hexafluoroacetylacetonate, Cr(hfa)₃, and the chelate solution was then analyzed by gas chromatography. It was found that Cr(tfa)₃ is the most suitable chemical form for this purpose. The method was profitably applied to the determination of chromium(III) incorporated in the six kinds of commerical products of potassium Chromate.     

Electrode processes and their kinetic parameters in the reduction and oxidation of Cr(III) and Cr(II) in molten CsCl

The reduction of chromium ions in the CsCl-CrCl₃ melt in wide concentration and temperature ranges is reported. It is assumed that the melt contains polynuclear chromium complexes. The reduction of Cr(III) to Cr(II) is a reversible one-electron process. The electroreduction of divalent chromium to chromium metal is an irreversible process involving dinuclear and mononuclear chromium complex ions. The electron transfer rate constant has been calculated for various temperatures and chromium chloride concentrations in the salt melt. The activation energy of electron transfer and its dependence on the CrCl₃ concentration in the electrolyte have been determined for the Cr(III) ↔ Cr(II) process.     

Simultaneous determination of hexavalent and total chromium in water and plating baths by spectrophotometry

A new spectrophotometric determination method of hexavalent chromium in waste water and plating baths is described based on the oxidation of beryllon III by chromium(VI) in 0.02M sulphuric acid medium. The decrease in the absorbance of beryllon III was measured at 482 nm with an apparent molar absorptivity of 5.15 x 10(4)1.mole(-1).cm(-1). Beer's law was obeyed for chromium(VI) over the range 0-25 mug/25 ml. After the oxidation of Cr(III) to Cr(VI) by ammonium persulphate, total chromium can be determined. Therefore, chromium(III) can be calculated by subtracting chromium(VI) from total chromium. The detection limit is 0.015 and 0.020 mug/25 ml for chromium(VI) and total chromium, respectively. A sensitive spectrophotometric method for trace Cr(III) and Cr(VI) in waste water and plating baths was developed with good precision and accuracy. The reaction is also discussed.     

溶胶-凝胶法制备Cr-基催化剂及其CO2氧化乙烷制乙烯

以硝酸铬为Cr源,正硅酸乙酯为Si源,采用溶胶-凝胶法制备了Cr质量分数为2.5%~10%的Cr-基催化剂;采用XRD、BET、SEM、H₂ TPR等分析测试技术对催化剂的结构进行了表征;在微型固定床反应器中对催化剂乙烷二氧化碳氧化脱氢制乙烯的催化性能进行了评价,并考察了反应条件对催化性能的影响。结果表明,催化剂中Cr的质量分数大于5%时,Cr的物相为Cr₂O₃,但Cr质量分数较低时,检测不到Cr的物相;Cr质量分数为5%的催化剂具有较大的比表面积,Cr质量分数变大或变小,催化剂的比表面积都会减小;催化剂的孔径在2nm左右,并与Cr的质量分数关系不大;Cr质量分数为5%的催化剂具有最好的催化活性,在750℃的反应条件下,乙烷和二氧化碳的转化率可达79.29%和23.74%,乙烯的收率可达67.91%;Cr质量分数为5%的催化剂具有适宜的氧化还原性能,这有利于乙烷和二氧化碳的转化。     

Speciation of Cr(III) and Cr(VI) by Means of Melamine-Urea-Formaldehyde Resin and FAAS

 A method is described for the quantitative preconcentration and separation of trace chromium in water by adsorption on melamine-urea-formaldehyde resin. Cr(VI) is enriched from aqueous solutions on the resin. After elution the Cr(VI) is determined by FAAS. The capacity of the resin is maximal at ∼ pH 2. Total chromium can be determined by the method after oxidation of Cr(III) to Cr(VI) by hydrogen peroxide. The relative standard deviations (10 replicate analyses) for 10 mg/L levels of Cr(VI), Cr(III) and total chromium were 1.5, 3.5 and 2.8% respectively. The procedure has been applied to the determination and speciation of chromium in lake water, tap water and chromium-plating baths.     

Flame Atomic Absorption Spectrometric Determination of Total Chromium and Cr(VI) in Cigarette Ash and Smoke using Flow Injection/Hydraulic High-Pressure Sample Introduction

Total chromium and Cr(VI) contents of cigarettes, ash, and smoke formed while burning cigarettes were determined. The determinations of chromium species were carried out according to procedures developed earlier. Cr(VI) was determined in a combined system, which involves a flow injection (FI) sorption preconcentration system, hydraulic high-pressure nebulization (HHPN) sample introduction technique, and flame atomic absorption spectrometric (FAAS) detection. The total chromium of samples in Cr(VI) form was determined in this same combined system after ashing cigarettes at 800°C [after total conversion of Cr(III) of the sample to Cr(VI)]. It was found that while burning cigarettes 0.8–1.2% of the original chromium content of the cigarettes comes to smoke in the toxic Cr(VI) form.     

The effect of Cr(III)-organic complexes on the determination of inorganic chromium species in groundwater by ammonium pyrrolidinedithiocarbamate–methylisobutylketone extraction procedure

Groundwater samples collected from a tannery contaminated area were analyzed for chromium species with the objective of investigating the interference of Cr(III)-organic complexes in the determination of Cr(VI) using APDC–MIBK extraction procedure. The contribution of Cr(III), Cr(VI) and Cr(III)-organic complexes towards total chromium ranged between 2 and 61%, 27 and 86%, and, 6 and 23%, respectively. The Cr(III)-organic complexes were not extractable by APDC–MIBK, however, HNO₃ digestion released the organic bound Cr(III). Interference of organic bound Cr(III) in Cr(VI) determination due to MIBK soluble Cr(III) was not observed. Significant difference between total dissolved chromium determined after appropriate digestion procedure, and the sum of dissolved Cr(III) and Cr(VI) determined indicates the presence of the Cr(III)-organic complexes. MIBK extraction of samples without APDC is an useful way to check the extractability of organic bound Cr(III). The presence of soluble Cr(III)-organic complexes thus add complexity to chromium speciation analysis by APDC–MIBK procedure.     

Analytical speciation of chromium in in-vitro cultures of chromate-resistant filamentous fungi

In this work, different analytical speciation schemes have been used to study the reduction of Cr(VI) by a chromate-resistant strain of filamentous fungi Ed8 (Aspergillus sp), indigenous to contaminated industrial wastes. As demonstrated previously, this strain has the capability to reduce chromate present in the growth medium without its accumulation in the biomass, yet the reduced chromium end-products have not been characterized. Liquid growth medium, initially containing 50 mg L(-1) Cr(VI), was analyzed for Cr(III)/Cr(VI) and for total Cr at different time intervals (0-24 h) after inoculation with fungi. Three hyphenated procedures, based on the Cr(III)-EDTA formation and species separation by anion-exchange or ion-pairing reversed-phase chromatography with ICP-MS or DAD detection were used. The results obtained for Cr(VI) in each case were consistent, demonstrating efficient reduction of chromate during 24 h of Ed8 growth. However, pre-column complexation with EDTA did not ensure complete recovery of the reduced forms of chromium in the above procedures. An alternative speciation scheme, based on extraction of Cr(VI)-benzyltributylammonium bromide (BTAB) ion pairs into chloroform and subsequent determination of residual chromium by ICP-MS has provided evidence on the effective conversion of chromate into reduced chromium species in the growth medium. The results indicate the feasibility of using Ed8 strain for chromate bioremediation purposes. Analytically it can be concluded that speciation of chromium in biological systems should not be limited to its two most common oxidation states, because the actual reduced chromium species are not converted quantitatively to Cr(III)-EDTA.