示波极谱法测定食品包装材料中的游离苯酚

探讨苯酚的亚硝化反应极谱还原波的最佳形成条件及共存物质的影响,建立了用单扫描示波极谱法测定食品包装材料中游离苯酚的简便方法。在峰电位-0.47V(vs·SCE)处,苯酚的亚硝化产物二阶导数的峰高与苯酚浓度在0.02～0.8μg/10 mL呈良好的线性关系,苯酚的检出限为0.002 mg/L。与比色法相比,该法蒸馏时间缩短了2/3,取样量减少至1/40,不使用有机溶剂,每小时可分析30～40份样品。     

级联人工神经网络结合单扫描示波极谱法同时测定对硝基氯苯和邻硝基苯酚

在pH 6.5的0.3 mol·L-1氯化钾介质中,在电位值-0.71 V 及-0.74 V处可分别见到对硝基氯苯及邻硝基苯酚的灵敏极谱峰,可分别对此两种化合物进行测定,但因两者相互干扰不能在混合物中同时测定.将改进的小波神经网络与BP神经网络相结合,提出一种新的混级联神经网络结构,并用于单扫描示波极谱法同时测定对硝基氯苯和邻硝基苯酚.通过对网络结构的优化和网络参数的调整,加快了训练速度,提高了预测的准确度.该法用于混合样品中同时测定对硝基氯苯和邻硝基苯酚,其相对误差和回收率分别为3.76%,96.2%;4.05%,96.0%.     

对硝基苯酚共存下甲基E605的极谱测定

而其对人畜毒性则比E605低,因此人们较喜欢采用甲基E605。甲基E605含量测定的方法有多种如容量法、比色法、极谱法等。在这些方法中对硝基苯酚     

固体核磁法研究苯酚与聚4-乙烯基吡啶的相互作用

采用高速魔角旋转(MAS)偶极滤波结合氘代稀释固体核磁技术, 研究了极性吸附分离材料聚乙烯吡啶与氘代苯酚之间的相互作用. 固体核磁结果表明, 聚乙烯吡啶与苯酚之间存在强的氢键作用, 与液体氢谱结果一致. 由MAS中水峰强度在吸附前后的变化揭示了苯酚部分置换了聚乙烯吡啶中的水, 且苯酚和聚乙烯吡啶氢键作用位点在靠近N的一端. 此种方法对于原位研究吸附剂的吸附机理以及新型吸附分离材料的设计具有重要的指导意义.     

单扫描示波极谱法测定巯基乙酸的研究

在H2SO4－NH4OAc(pH3．5）溶液中，巯基乙酸有一灵敏的还原波。当使用单扫描极谱法时，其二阶导数峰电位位于－0．320V（vs.SCE)。用直流极谱法，单极描极谱法和循环伏安法研究了该体系的极谱行为和电极反应机理。结果表明，当使用单扫描极谱法时，该体系属于有吸附性的准可逆过程，测得电极反应电子转移数n=1,H^ ，反应数n′＝1。用单扫描极谱法可测定巯基乙酸，测定的线性范围为0.04-2.0mg.L^-1，该方法用于冷烫液中巯基乙酸的测定，结果满意。     

工业废水中微量苯酚的交流示波极谱滴定

工业废水中微量污染物苯酚用交流示波极谱滴定可简单而快速地测定。准确分取部分过滤后的试样在氯化钾底液中以苯胺作指示剂,在不断搅拌下用0.020 00 mol.L-1氢氧化钾标准溶液滴定,用汞膜电极作指示电极,银汞电极为参比电极。苯胺的示波极谱图上出现切口时即为滴定终点。根据氢氧化钾标准溶液滴定的体积计算试样中苯酚的含量。此滴定至终点的溶液的pH值经预先试验测定为11.27,而6 g.L-1苯胺溶液1 mL在氯化钾底液中当出现切口时的pH值为11.3。苯胺在此方法中的作用为指示剂,以其示波极谱图上出现切口指示滴定终点。此方法应用于废水样品分析,回收率在97.3%~104.0%之间。     

单扫描极谱法测定水中痕量苯酚

苯酚与对硝基苯胺的重氮盐偶合后,在０．０３ｍｏｌ／Ｌ Ｎａ２ＣＯ３－０．０３ｍｏｌ／Ｌ ＮａＨＣＯ３－１６０ｇ／Ｌ乙醇介质中,偶合产物在单扫描示波极谱上产生一个灵敏而精晰的吸附还源波,波高与苯酚浓度在０．００５～０．５ｍｇ／Ｌ范围内呈良好线性关系,峰电位为－．０５８Ｖ（υｓ,ＳＣＥ）,方法检出限达０．００２ｍｇ／Ｌ。已用于天然水中痕量苯酚的测定。     

8—羟基喹啉极谱法测定硝酸根的研究

在浓硫酸介质中，８－羟基喹啉发生硝化反应，产物在ｐＨ９．０的ＮＨ３－ＮＨ４Ｃｌ缓冲液中，用单扫描极谱法可获得灵敏极谱波，导数波高与硝酸根浓度在每ｍＬ０．０２～２．２μｇ范围成正比，检测限为每ｍＬ０．００３μｇ。研究了极谱波行为，推测了电极反应机理。本法可用于天然水样中硝酸根的测定     

Mo（Ⅵ）—N—苯甲酰苯基羟胺络合物的极谱催化波

本文研究了Ｍｏ（Ⅵ）与Ｎ－苯甲酰苯基羟胺络合物的极谱行为，讨论了六次甲基甲胺在形成极谱电流时的作用。在ＨＡｃ－ＮａＡｃ介质中，Ｍｏ（Ⅵ）－ＢＰＨＡ络合物在单扫示波极谱上，于－０．４５Ｖ产生一灵敏的吸附催化波。     

极谱法在环境分析中的应用

<正> 随着科学技术的发展,对极谱法提出了进一步的要求,快速、高灵敏度和高分辨率的极谱方法诸如溶出伏安法、催化极谱法、示波极谱、交流极谱、方波极谱和脉冲极谱法等相继问世。极谱法用于环境样品分析广泛采用了新技术,某些元素的伏安法或与脉冲极谱相结合的方法其灵敏度可与无火焰原子吸收光谱法比美。极谱法设备简单,价格低廉,加之方法在不断改进,因而在成份复杂的环境样品分析中得到日趋广泛的研究和应用。     

溴酸钾氧化酸性铬深蓝催化动力学极谱法测定痕量钒

在0.15mol·L~(-1)H_2SO_4介质中,以酒石酸作活化剂,Ⅴ(Ⅴ)对溴酸钾氧化酸性铬深蓝的反应具有强烈的催化作用,以极谱法监测催化反应过程中酸性铬深蓝浓度的变化,建立了测定痕量钒的催化动力学新方法。钒的线性范围为0.10～7.0ng·ml~(-1),检出限为0.05ng·ml~(-1),应用于人发中痕量钒的测定,结果满意。并对酸性铬深蓝的极谱特性进行了初步的探讨。     

Determination of the ratio of copper(I) to copper(II) present as traces in ionic crystals

A polarographic method is described for the determination of traces of copper in ionic crystals, which also allows the determination of the ratio of the concentrations of copper(II) and copper(I).     

Review of adsorptive stripping voltammetric methods for cobalt determination in the presence of a zinc matrix

Different polarographic and voltammetric methods for the determination of Co in the presence of a large excess of zinc are reviewed. Adsorptive stripping voltammetry with in-situ matrix exchange and catalytic adsorptive stripping voltammetric methods are recommended for monitoring Co traces in zinc plant electrolyte. The principles of the catalytic adsorptive stripping voltammetric methods for Co determination are presented. The correct selection of the investigated supporting electrolytes, enabling the monitoring of Co traces in a zinc plant electrolyte by means of catalytic adsorptive methods is also discussed. The catalytic adsorptive voltammetric procedures offer the possibility of the determination of Co or Co and Ni traces in metallic zinc and zinc salts.     

Trace determination of platinum-II. Analysis in ores by pulse polarography after fire-assay collection

A pulse-polarography method is described for the determination of traces of platinum in ores after fire-assay separation and preconcentration. The silver bead from the fire assay is dissolved and treated with ammonia and ethylenediamine to produce a sensitive catalytic polarographic wave. Measurement of the wave by differential pulse polarography allows determination of Pt with a detection limit of 0.0025 ppm. Platinum in ore samples was determined in the range 0.1-0.9 ppm and a correlation coefficient of 0.98 was obtained on comparison with AAS results.     

Polarographic determination of trace amounts of thorium

A sensitive linear-sweep polarographic method for the determination of thorium is described. It is based on the thorium complex with Xylidyl Blue I (XBI) in a medium containing ethylenediamine, 1,10-phenanthroline, oxalic acid and ninhydrin, at pH 10.5-11.5. The complex has been proved to be Th(XBI)(2), with log beta' = 9.6. The method can be used to determine trace amounts of thorium over the range 3.5 x 10(-8)-3 x 10(-6)M. The detection limit is 1 x 10(-8)M. A solvent extraction procedure is necessary to eliminate interference from several cations. The method has been applied to determination of traces of thorium in minerals, with good results.     

Spurenanalyse von huminstoffen im trinkwasser: The d.c. polarographic determination of traces of humic substances in potable waters

(The d.c. polarographic determination of traces of humic substances in potable waters) The inhibiting effect of a tri-n-butylphosphate layer adsorbed at the mercury drop on the polarographic wave of copper(II) is reduced by humic substances. This effect can be utilized to determine humic substances in the range 0.05–1 mg l^-1. The standard substance used was isolated from peaty water. Humic and fulvic acids are not differentiated but amino acids, peptides and polyhydroxy compounds do not interfere.     

氧极谱催化波法测定二苯胺

本文报道一种极谱测定二苯胺的新方法,它是基于二苯胺引起的氧极谱催化波.这个氧极谱催化波是由于二苯胺催化了电生超氧离子O_2~(-)的歧化反应产生的.本方法简单方便,有良好选择性.应用本方法测定了化工原料二苯胺的含量,结果令人满意.     

Zur Bestimmung von β-Aminocrotonsäureester nach Migration in Lebensmittel

β-Aminocrotonic esters are of great importance as stabilizers for the production of clearly transparent food packaging of PVC. For the purpose of studying the migration into foods a thin-layer Chromatographic and a polarographic method were elaborated. The TLC method consists of the visual comparison of the intensity of the spots after treatment with Fast Blue B salt. The polarographic determination is carried out after nitrosation of the stabilizer. By the TLC method 10^?7 g of ester per spot are still detectable; the concentration which is still determinable by cathode-ray polarography is 5×10^?7 g of ester and by conventional d.c. polarography 5×10^?6g of ester per ml of final solution. After extraction with acetonitrile traces of the stabilizer which are migrated into edible oil are still determinable down to 2 ppm by the methods described.     

Differential pulse polarographic determination of tellurium. Application of catalytic hydrogen current

Tellurium deposited on the DME displaces the reduction potential of hydrogen and this results in the formation of a catalytic hydrogen current. Differential pulse polarographic measurement of the corresponding peak enables the determination of traces of tellurium down to the 1 ppb level. Using the method of standard addition, tellurium can be determined in the presence of all the metals usually accompanying tellurium in natural and industrial materials. In the cases when the material analyzed contains a larger excess of cadmium, silver or selenium, the separation of tellurium by extraction with methylisobutylketone should be employed.     

Ultra trace analysis of molybdenum by differential pulse polarography and adsorptive stripping voltammetry in the presence of 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone

Summary Different polarographic and voltammetric techniques for the determination of molybdenum at the trace level have been investigated. As a result, a new high-sensitivity procedure for the determination of molybdenum by adsorptive stripping voltammetry was developed. The method is based on the reaction of molybdenum(VI) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid) to produce a complex which is absorbed onto mercury at –0.20 V (vs. Ag/AgCl, 3 mol/l KCl) from pH 2.7 solution. The cathodic stripping peak at –0.62 V can be used to determine molybdenum with a detection limit of 0.02 ng/ml after 5 min deposition time. The relative standard deviation for the determination of 0.1 ng/ml Mo after 5 min stirred collection was 6.6%. Interference from various inorganic ions and organic substances are reported. The method was applied to the determination of molybdenum traces in waters; interfering organic substances in polluted waters were destroyed by oxidative digestion in a microwave oven.