重铬酸钾滴定法测定铁矿石中亚铁含量方法的改进

建立了以邻菲罗啉(Phen)、氢氟酸(HF)和硫酸(H_2SO_4)为溶剂溶解试样,用重铬酸钾滴定法测定铁矿中亚铁含量的新方法。在强酸(H_2SO_4)介质中,Fe~(2+)与邻菲罗啉和氟离子形成稳定的络合物,有效地防止了亚铁离子的氧化。在硼酸、硫磷混酸溶液中,以重铬酸钾溶液滴定,并对溶样过程以及滴定过程中的一些条件进行了优化。方法用于铁矿中氧化亚铁的测定,经过国家标准样品以及单位管理样品分析数据对比,方法的重现性较好,相对标准偏差(RSD)<1%,方法无需在铂金坩埚进行熔样,具有准确度高、重现性好、简单、快速、经济等优点,在实际应用中得到满意的结果。     

磷灰石中微量氧化亚铁的测定

磷灰石多产于沉积岩中,也有产于变质岩和火成岩,常见的伴生元素为硅、铁、铝、锰、镁、钾、钠和稀土等,一般简分析只测定酸不溶物、五氧化二磷,全分析则根据分析要求及光谱资料确定增加分析项目,对磷灰石中氧化亚铁的测定是全分析中的一个指标,本法是基于在邻菲罗啉存在下,用硫酸-氢氟酸分解矿样,调节溶液的pH值在3～6的范围内,二价铁离子与邻菲罗啉形成桔红色络合物,借以进行比色。     

铸造锌合金中铜的测定-EDTA分光光度法

本文采用醋酸-醋酸钠缓冲溶液控制PH值.用EDTA作显色剂测定锌合金中的铜,同时有利用EDTA掩蔽锌、铝等元素以消除其干扰.Cu+2与EDT生成11蓝色络合物,该络合物溶液的最大吸收波长在730mm处,表观摩尔吸光系数为93.2.铜量在0～15 mg/100ml符合比尔定律.虽然显色反应的灵敏度不高,但通过增加取样量、加大比色皿厚度,仍可用于锌合金中0.x～10%的铜的测定.本法试剂用量少,操作简便、快速,精密度高,结果令人满意.     

三次函数拟合光度法测铁矿石中的Fe2O3

1前言 　　铁矿石中Fe2O3的测定,通常采用铋盐返滴定法和重铬酸钾滴定法测定,光度法测定铁矿石中的Fe2O3尚未见报道,本文在参考邻菲罗啉光度法测Fe2O3的基础上,提出采用抗坏血酸-邻菲罗啉光度法测定样品、三次函数拟合处理数据,形成了一种新的试验方法,使得铁矿石样品可以通过光度法进行测定.……     

一种新型的二邻菲咯啉硫酸锌配合物的合成及晶体结构

以1,10-邻菲咯啉和硫酸锌合成了新型的硫酸配合物[2ZnSO_4(Phen)2H_2O]·3CH_3OH·H_2O,并用X-射线衍射分析对其结构进行了表征。结果表明,该晶体属于单斜晶系,空间群为Pc,晶胞参数为:a=16.8986(14)A,b=12.0606(11) A,c=12.3138(12) A,β=94.748(2),F=2 501.0(4) A³,Z=2,F(000)=1 212,R_1=0.0331,R_2=0.0620。在配合物中,中心离子金属锌(Ⅱ)除与2个邻菲咯啉中的氮原子配位外,特别的是与硫酸基团中氧的配位。在配合物的2分子中,有一分子的硫酸基团2个氧与锌(Ⅱ)配位,而另一分子硫酸基团只有1个氧与锌(Ⅱ)配位。     

经典方法测定朱砂安神丸中朱砂的含量

目的通过经典方法对朱砂安神丸(水蜜丸)中朱砂的含量进行测定。方法采用铜试剂滴定的容量法,试样用盐酸与硝酸混合酸(1∶1)分解,在pH>8的氨性溶液中,铜试剂与汞(Ⅱ)生成白色沉淀(二乙胺基二硫代甲酸汞),过量的铜试剂与Cu2+生成黄色沉淀(二乙氨基二硫代甲酸铜),其黄色沉淀可用四氯化碳浓集,以指示终点。结果 3个批次朱砂安神丸中所测得朱砂的平均含量(以硫化汞计算)为14.10%,RSD为0.5%;精密度试验测定,平均含量为14.40%,RSD为0.25%;平均回收率为96.45%,RSD为1.94%。结论本法具有干扰因素少、操作方便的特点。测定范围从万分之几至百分之几十,故适用于本制剂朱砂中硫化汞的含量测定。该方法操作简便、结果准确、重现性好。为将硫化汞含量作为制剂质量控制的指标之一来进一步提升药品质量标准提供了实验依据。     

超声辅助分散液液微萃取与分光光度法联用测定痕量铜的研究

以有机溶剂CCl_4为萃取剂,铜试剂为显色剂,超声辅助乳化2min,建立了金施尔康中铜含量的超声辅助分散液液微萃取与分光光度法联用的新方法。研究了吸收曲线、显色剂的用量、超声时间、萃取剂的选择与用量、离心时间、离心转速、溶液的浓度、复溶剂的选择及共存离子的干扰等影响因素。在最佳实验条件下,铜含量在4.3~6.7μg/mL范围内呈线性关系,线性回归方程为y=0.2506x-0.8797,相关系数R=0.9989,检出限为1.549μg/mL,加标回收率为96.28%。该方法可用于药物金施尔康中的铜含量的测定。     

乙二醇——氧化钙体系的反应动力学研究

本文采用电导法从动力学角度对乙二醇——氧化钙体系的反应机理、以及溶液温度、样品细度、乙醇和其它试剂对反应速度的影响进行了研究,为水泥熟料中游离氧化钙快速测定的条件选择提供了理论和实验上的依据。     

用化学发光免疫法检测有机氯农药DDTs的残留量

建立了检测有机氯农药DDTs残留的化学发光免疫分析技术(chemiluminescence immunoassay,CLIA),以鲁米诺和过氧化氢作为化学发光底物,测定样品中有机氯农药DDTs残留。结果表明:发光底物液非催化下,5～7 min后发光值较稳定;在发光底物液酶催化下,反应10 min接近峰值;DDTs标准曲线线性范围为0.05～25 ng/mL,标准样品DDTs浓度与发光值呈现很好的线性相关,线性方程为y=-63.806x+13426,R2=0.9945,检测最低限为0.05 ng/mL;回收率为91.4%～107.8%。     

EDTA络合滴定法快速测定矿石中钙、镁

试样用盐酸、硝酸、氢氟酸、高氯酸分解,在pH值为6～9时,经六次甲基四胺-铜试剂分离铁、铝、镍、钴、铅、锌、铜、镉、锰等干扰元素后,在pH=10的氨水和氯化铵缓冲溶液中,以酸性铬蓝K-萘酚绿B为指示剂,用EDTA络合滴定法测定钙镁合量;另在氢氧化钾溶液中,用钙试剂为指示剂,以EDTA络合滴定法测定钙量,从而计算镁的含量。当样品钙高镁低或者镁高钙低时,低含量的镁量或钙量(<5%)可用电感耦合等离子体原子发射光谱(ICP-AES)法准确测定,使结果更准确。实验中对三个标准样品中的钙和镁进行多次测定,结果与认定值相符,相对标准偏差在0.69%～1.3%(n=7),加标回收率在99%～102%。方法实用性强,已经成功应用于各类矿石中钙镁的检测。     

Selenium and its redox speciation in rainwater from sites of Valparaiso region in Chile, impacted by mining activities of copper ores.

The determination of the total concentration of selenium does not provide sufficient information about its toxicity and its bioavailability. The determination of its chemical forms is the basis for understanding the biogeochemical cycle in terrestrial and aquatic ecosystems and for detecting the species which might be toxic to biota. In this work we describe an analytical procedure to carry out the redox speciation of selenium present at ultratrace levels in rainwater from sites of Valparaiso region in Chile, impacted by mining activities of copper ores. A simple preconcentration step of the rainwater sample on a rotavapor system, in vacuum at low temperature permits the concentration of the different redox selenium species until levels quantifiable by sensitive techniques such as differential pulse cathodic stripping voltammetry or by spectrometric techniques, based on the hydride generation and detection by atomic absorption or atomic fluorescence spectrometry. These techniques coupled to redox chemical reactions allow the redox speciation of selenium. The results show that the open evaporation system can be used to concentrate water samples when the aim of the analysis is the determination of the total selenium concentration. On the contrary, to carry out its redox speciation only the preconcentration performed on rotavapor system, in vacuum can be used. When synthetic solutions containing different redox species of selenium, at ultratrace levels, were slowly evaporated on open system, Se(II) and Se(IV) were oxidized. The optimized procedure was then applied to the selenium determination and its redox speciation in rainwater samples collected in sites impacted by mining activities of copper ores. It was found that the amounts of total selenium in rainwater, as copper, from Puchuncavi valley decrease exponentially with the distance from the source, indicating that these elements in this region arise from the industrial complex Las Ventanas. In the redox speciation of selenium, Se(IV) and Se(VI) were the species found in all rainwater samples analyzed, providing selenium in species which are most favorable for their uptake by the vegetation grown in these soils.     

Trace metal species in fresh waters

A recently proposed trace metal speciation scheme was applied to the determination of the chemical forms of copper, lead, cadmium and zinc in four natural fresh waters and a tap water. Studies were also made on the reliability of the technique, and of the effect of various methods of storage on the speciation results. The measurements showed that (a) copper in the river and reservoir samples was associated mainly with organic matter, probably organic colloids; (b) lead was divided between stable inorganic and organic forms, but one particular inorganic lead species predominated; (c) cadmium existed almost entirely as labile ionic forms; (d) zinc was divided between labile ionic species and a stable inorganic form; very little zinc was associated with organic colloids, and (e) the trace metals were not combined with inorganic colloids. Samples stored in polyethylene containers for over three weeks at 25°C or 4°C showed little change in either total metal concentration or metal speciation. Freezing, however, caused some irreversible changes.     

The determination of cadmium. lead, copper and zinc in ground water, estuarine water, sewage and sewage effluent by anodic stripping voltammetry

Anodic stripping voltammetry (ASV) using the thin-film mercury electrode was shown to be a successful technique for the determination of total (free plus complexed) trace metal concentrations in various types of aqueous sample. The method developed involved the minimum of sample treatment and required only simple and inexpensive equipment. The practical limit of sensitivity was about 0·1 μg I⁻¹ for cadmium, lead and copper. The determination of zinc was found to be complicated by the formation of an intermetallic compound with copper. Interference by other trace metals and by complexing agents was investigated. Photochemical oxidation for the decomposition of complexes of the metals with organic ligands in filtered sewage and sewage effluent was found to be successful, although the process is slower for cadmium than for the other metals. Good agreement with atomic absorption spectroscopy was obtained for all the types of aqueous sample investigated. Possible improvements of the ASV technique are discussed.     

Detection of tannic acid at trace level in industrial wastewaters using a highly sensitive chemiluminescence method

A novel flow injection procedure was developed for the determination of tannic acid in industrial wastewaters based on the enhancement by tannic acid of the chemiluminescence from luminol-K3Fe(CN)6-OH- system. The method has the merits of higher sensitivity, higher selectivity, wider linear range, simpler instrumentation. It is applicable for the determination of tannic acid in the range of 3.0 x 10(-10)-1.0 x 10(-7) mol/L with a detection limit of 1.0 x 10(-10) mol/L. The relative standard deviation is 2.7% for the determination of 1.0 x 10(-8) mol/L tannic acid (n = 11). The method has been successfully used to determine tannic acid at trace level in industrial wastewaters from brewery and tannery.     

The polarographic determination of trace amounts of cyanide

A method is proposed for the indirect determination of trace amounts of cyanide. After release and distillation of the cyanide, which is collected in 1·0 M sodium hydroxide, the cyanide is reacted with a known and excess amount of copper(II) ions.The excess of the Cu(II) ions is determined by polarography, and from the amount of Cu(II) which has reacted, the amount of cyanide originally present is calculated.     

The effect of uric acid on outdoor copper and bronze

Bird droppings are often quoted as a decay agent for outdoor goods, in particular buildings and statues. Undoubtedly, they represent one of the major causes of aesthetic damage on outdoor materials, but the real chemical damage they are able to induce, in particular on metals, is not so well studied. This work focused on the short term role of uric acid, the main constituent of bird urine, with respect to copper, which make such an important contribution to architectural elements of buildings and outdoor sculpture. Preliminary results of laboratory tests and analyses on real exposed samples showed that uric acid chemically affects copper and bronzes: the surface of the metal is modified and copper urates formed. Also natural patina, formed on statues and roof, react with uric acid, even if it seems to afford some protection toward bird droppings. In general, experimental results confirm that the potential chemical damage by bird droppings is significant when considering external cultural heritage such as statues, metal monuments and buildings with historic copper roofs.     

Function and homeostasis of coper and zinc in mammals

Recently there has been great interest in the determination of levels of trace elements in biological systems. The goals of many researchers in this field have been: understanding the roles of micronutrients in biochemical processes and the evaluation of biological mechanisms that maintain tissue concentrations at relatively constants levels. The biochemical and physiological functions of the micronutrients copper and zinc have been reviewed with emphasis on factors, both endogenous and exogenous, associated with the maintenance of homeostatic levels in mammalian sera. Understanding the mechanisms affecting homeostasis will provide a background necessary for the application of data on serum trace minerals in the diagnosis and prognosis of disease states.The general roles of copper and zinc in animal nutrition may be understood by evaluating physiologic changes associated with deficiency states of these essential elements. Deficiencies are associated with antagonisms and interactions from other elements and from chelating organic compounds as well as with primary deficiencies due to insufficient dietary levels. Biochemical and physiochemical properties of copper and zinc biomolecules are discussed with primary emphasis on the forms of these metals in serum. Also discussed in detail, are the effects of disease, radiation exposure and environmental factors on serum and tissue copper and zinc levels.     

Chemical catalyst interference in the winkler titration determination of dissolved oxygen—a method for correction

A new procedure involving the measurement of a chemical blank is introduced to correct the cobalt interference effect associated with the Winkler titration analysis for dissolved oxygen. Unsteadystate reaeration studies employed for mechanical aerator evaluation tests show that when sodium sulfite is used in the presence of a cobalt ion catalyst to deoxygenate the test basin water, a chemical interference is detected in the Winkler determination of dissolved oxygen content. The source to which this influence is attributed is a chemical precipitate that forms in the reaeration process. Evidence suggests that the cobalt (II) ion is oxidized to the (III) oxidation state forming a cobalt (III) hydroxide in the alkaline test environment. Upon acidification of the test samples during the Winkler procedure, the cobalt (III), a powerful oxidizing agent, is released and in turn effects an increase in the amount of free iodine released and measured by titration. The additional iodine liberated in this manner yields erroneous oxygen concentration values which are then used to calculate the oxygen mass transfer coefficient. Considerable deviation from the true value of the coefficient can result.     

Trace element reference values in tissues from inhabitants of the European Community. II. Examples of strategy adopted and trace element analysis of blood, lymph nodes and cerebrospinal fluid of Italian subjects.

The EURO TERVIHT (Trace Element Reference Values in Human Tissues), recently initiated, aims to establish and compare trace metal reference values in inhabitants from the different EC countries. The project anticipates international cooperation of specialized chemical and toxicological laboratories in Western Europe. In order to overcome the well known and intolerable high fluctuation in published trace metal concentrations in body fluids and tissues, which are mostly due to poor analysis, this paper gives recommendations and strategies for approaching 'background' values measurement practised in the EURO TERVIHT. The focus of the paper is more on quality rather than on quantity of data with particular aspects: (i) well-described protocol for the selection/composition of reference groups (extended epidemiological data plus clinical status); (ii) numerous pre-analytical factors, among which are of paramount importance are ultraclean laboratory air, container material, storage conditions at -20 degrees C; (iii) statistical treatment of the data and the expression of the analytical results (use of refined statistical analysis such as the Lilliefors test to define the type of distribution, normal or log-normal). Results reported here concern the determination of trace elements in whole blood of more than 350 Italian subjects which allowed the proposal of 'reference values' for 12 elements. In lymph nodes and cerebrospinal (CSF) the degree of information acquired is only sufficient to suggest 'indicative' of 'informative' values.     

Sampling and storage of natural waters for trace metal analysis

Methods for the collection, preservation and storage of natural water samples for the analysis of trace levels of heavy metals have been critically reviewed, with particular reference to the analysis of zinc, copper, lead, cadmium and mercury. Recommended prodecures are given which minimise the problems of sample contamination and adsorption losses. Carefully cleaned high-density polythene or Teflon containers are recommended for both sampling and storage, with a storage temperature of 4°C. Acidification to 0.05 M H⁺ with nitric acid is desirable, except in speciation studies. For mercury analysis the addition of an oxidant or complexing agent is also necessary.