Optimization of Flow Injection On-Line Microcolumn Preconcentration of Ultratrace Elements in Environmental Samples prior to Their Spectrochemical Determination

The preconcentration of some elements such as Cd, Co, Ni, and V(IV) was modeled in the presence of complexing agents such as citrate and oxalate at high Ca, Mg, and sulfate concentrations on iminodiacetic acid/ethyl cellulose (IDAEC), a chelating cellulose. The effect of the species present in the solution was studied after construction of the species distribution curves using critical, estimated, and measured stability constants. The stability constants of the IDAEC chelates were determined potentiometrically. The constants were calculated or estimated using computer programs. The diagrams calculated in homogeneous media were used for optimization of the flow injection on-line preconcentration for analysis of ultratrace metals in the highly mineralized water “Hunyadi.”     

Determination of trace metals and speciation of chromium ions in atmospheric precipitation by ICP-AES and GFAAS

Sampling and analytical techniques used for determining trace metal concentrations in atmospheric precipitation waters collected in Hungary are presented. The results of the analyses are briefly discussed and special attention is devoted to chromium speciation. For the preconcentration of the trace metals a chelating cellulose, iminodiacetic acid ethylcellulose (IDAEC) microcolumn was used in a flow-injected system. Cd, Co, Cu, Fe, Mn, Ni, Pb, Ti, V and Zn were determined by ICP-AES. In precipitation water the concentrations of the trace elements were in the 0.1-50 mug/l. range. The two forms of chromium, Cr(III) and Cr(VI) were separated using IDAEC and the anion exchanger diethylamine ethylcellulose, respectively. Cr was determined by GFAAS. In atmospheric precipitation the concentration of Cr(III) was in the range of 0.1-0.4 mug/l. while that of Cr(VI) in the range of 0.04-0.1 mug/l.     

The application of flow injection iminodiacetic acid–ethylcellulose membrane preconcentration and separation technique to atomic spectrometry

A flow injection-based on-line iminodiacetic acid–ethylcellulose (IDAEC) membrane preconcentration and separation technique was developed in the present work, which has the advantages of easy operation without membrane plugging problems; a high enrichment factor (more than 10 for most elements); a high sample throughput (30 samples h⁻¹). The characteristics of the IDAEC membrane were systematically studied, including the effect of sample flow rate and analyte concentration on breakthrough point; dynamic capacity and the lifetime of the IDAEC membrane. The technique was successfully applied to pond and seawater analysis in which all elements studied are in ng ml⁻¹ level. The analytical performance was verified with recovery of a standard addition from seawater. Satisfactory results were obtained.     

Determination of trace elements in pharmaceutical substances by graphite furnace atomic absorption spectrometry and total reflection X-ray fluorescence after flow injection ion-exchange preconcentration

Flow injection iminodiacetic acid ethyl cellulose (IDAEC) microcolumn preconcentration and graphite furnace atomic absorption spectrometry determination of trace metals (Cd, Co, Ni, Pb) were carried out without decomposition of the drug matrix. The two forms of chromium Cr(III) and Cr(VI) were separated using IDAEC and anion exchanger diethylaminoethyl (DE)-cellulose, respectively. The detection limits of trace elements in pharmaceutical substances (sugars, sorbitol, mannitol, paracetamol, amidopyrine, chloral hydrate) after a 10-fold preconcentration in 1–5% m/v solution of pharmaceuticals were in the 0.3–29 ng g⁻¹ range. The measured concentration of trace elements in substances investigated was below 100 ng g⁻¹. The spike recovery was close to 100%. The capability of total reflection X-ray fluorescence technique for the determination of trace elements in pharmaceuticals with and without preconcentation was explored.     

On-site classification of manganese forms in natural waters by membrane filtration and chelating exchange

The possibility of chemical speciation of manganese was studied to explain the behavior and fate of trace metals in the aquatic environment. An operationally defined on-site preconcentration and fractionation scheme was developed that was based on the difference in the thermodynamic and kinetic behavior of manganese species. This scheme was used to distinguish between the different manganese forms in river and karstic groundwater. According to the elaborated “in field” procedure, the water sample was pressed through a membrane filter (0.22 μm) coupled to an imino diacetic acid–ethyl cellulose (IDAEC) chelating exchanger minicolumn by means of a syringe, followed by a batch enrichment. The fractions were analyzed by graphite furnace atomic absorption spectrometry. The dissolved manganese part was in the range of 0.5–1.5 μg l⁻¹ and the on-site spike addition resulted in a satisfactory recovery. The binding behavior of manganese in different classes was characterized by means of stability constants of the Mn-IDAEC complexes.     

Graphite Furnace Atomic Absorption Spectrometry Determination and On-line Preconcentration of Palladium

Palladium was determined in pharmaceuticals by direct graphite furnace atomic absorption spectrometry (GFAAS) method. The detection limit was 0.1 μg/g in 5% solution; the recovery of 0.5–2.0 μg/g Pd spike was close to 100%. The flow injection GFAAS method was worked out using oxime and iminodiacetic acid ethyl cellulose (IDAEC) microcolumns for preconcentration of Pd in aqueous and 50% methanol solutions. The optimal pH range for preconcentration was 2–5. At 20-fold enrichment the detection limits for Pd were 0.39 μg/liter for oxime cellulose and 0.42 μg/liter for IDAEC.     

On-line preconcentration and GFAAS determination of trace metals in waters

An on-line separation preconcentration system coupled to electrothermal (graphite furnace) atomic absorption spectrometry was developed. A miniature column packed with iminodiacetic acid ethyl cellulose (IDAEC) was inserted into the loop. A peristaltic pump was used to deliver solutions. A flow of air was driven into the packed column, evacuating it between sample loading, washing and elution. The retained analyte was introduced on-line to graphite furnace using countercurrent elution with HNO₃. The system was applied for the determination of V, Co and Pb in medicinal mineral water samples, and nickel in sea water samples. The detection limits (3σ) were 0.058, 0.022, 0.067, 0.062 μg/l for Co, Pb, V, and Ni, respectively. The R.S.D. (n=5) was <5% at 0.4–1.0 μg/l concentration range.     

Study of interference of pharmaceuticals with complexing characteristics in solid phase microextraction of lead on chelating celluloses

Trace lead impurities of drugs in 1-5% solutions can be preconcentrated on imino diacetic acid-ethyl cellulose (IDAEC). The buffered sample was loaded onto a chelating cellulose minicolumn by flow injection followed by the nitric acid elution and graphite furnace atomic absorption spectrometry (GFAAS) determination. The detection limit of the procedure depending on the concentration of drug solution is in the range 2-10 ng g^− 1. The bonding of lead to various pharmaceutical compounds appeared in reduced rate during preconcentration according to the competition between ligands. The first step was focused on the determination of the stability constants of the lead-chelating cellulose species. In the second step, the sorption was estimated from different pharmaceutical matrices considering the lead-drug interaction. In the third experimental step estimated sorption was compared with the determined values for some medicines like aspartic acid, penicillamine, captopril, N-acetyl-cysteine and its pharmaceutical product, ACC 200.     

Determination of noble metals by neutron-activation analysis

The scope and limitations of neutron-activation analysis in the field of the platinum metals are discussed. Special attention is given to interferences that occur in determination of noble metals in platinum metals and in natural samples. The problem of standards, carriers and chemical yield determination is emphasised. A recommendation is given of modern techniques for counting radionuclides formed by neutron activation of the platinum metals.     

垃圾焚烧飞灰中重金属的热稳定化条件及机理

研究了生活-农业混合型垃圾焚烧飞灰与单一生活垃圾焚烧飞灰（简称混合型飞灰与单一型飞灰）热处理过程中的重金属挥发特性与稳定化效果，并结合FT-IR、XRD检测手段对稳定化机理进行了探讨。结果表明，单一型飞灰中重金属的挥发性普遍高于混合型飞灰，垃圾源氯含量对重金属的挥发性有明显影响。飞灰中Mn、Cr不易挥发，Zn、Cu较易挥发，Pb、Cd挥发性很强，热处理温度超过1 000 ℃时挥发率都超过50%。800 ℃为相对最优的热处理温度，兼顾了热处理过程重金属稳定化与抑制挥发。800 ℃以上时飞灰形成了稳定的硅酸盐结构体系，是重金属热处理后难以浸出的主要机理。     

Relationships between the molar volumes of mixtures of elements and their compounds

The molar volumes of stoichiometric mixtures of Group I–III metals and Group V–VII nonmetals are compared with the molar volumes of MX compounds. The derivatives of the B-subgroup metals have the molar volumes larger than the mixtures. The compounds of A-subgroup metals have smaller volumes than the mixtures. A crystal-chemical interpretation of this fact is advanced.     

Direct-reading d.c. arc spectrometry for rapid geochemical surveys

A technique developed for the rapid quantitative analyses of metals in large suites of silicate materials is described. A direct-reading emission spectrometer interfaced to a dedicated minicomputer is used with d.c. arc excitation. Sample, buffer and arc parameters were chosen to promote reproducible selective volatilization. By partial integration of the line emission for the volatile metals, the spectrum background contribution is reduced, improving line to background ratios and permitting both “volatile” and “nonvolatile” metals to be determined in one burn.Preformed electrode cups are used in a specially designed arc chamber which incorporates a gas jet for controlled atmosphere and arc stabilization, and permits automatic electrode alignment as well as rapid and efficient cleaning between samples. No adjustment of the electrodes is made during the burn.One standard only is required for calibration since the working curves are linear over the concentration ranges of interest and a method of background correction using this same standard is described.A high rate of analysis as well as good accuracy and precision is achieved for 21 metals.     

High frequency titrations involving chelation with ethylenediaminetetraacetic acid: Complexation with rare earths

High frequency titrations have been utilized in studying the chelation of rare earth metals with ethylenediaminetetraacetic acid. The use of high frequency titrations for the determination of rare earth metals has also been studied. A procedure is proposed based on direct titrations with disodium ethylenediaminetetraacetate in buffered solutions. Excellent end-points are obtained and the method is accurate in the absence of other metals that might react with the titrant.     

Analysis of alloys of titanium,niobium and tantalum by ion exchange

A procedure for the analysis of alloys of titanium, niobium and tantalum is described. After dissolution the metals are separated by ion exchange in hydrochloric-hydrofluoric acid media. Finally the metals are determined spectrophotometrically,     

New masking liquids for the analysis of supported catalysts and functional materials by small-angle X-ray scattering

A new contrasting procedure is proposed for studying supported catalysts and functional materials by small-angle scattering. The main advantage over earlier analogues is the use of new masking liquids, which possess very low X-ray absorption at a relatively high density. A number of supported catalysts were studied using the new procedure, and almost complete agreement of the particle-size distributions of supported metals with transmission electron-microscopic data was demonstrated. The use of the new contrasting procedure on a typical small-angle diffractometer makes it possible to obtain the particle-size distributions of metals in supported catalysts containing noble metals at a level to 0.1 wt %.     

On Passivating Action of Silicate-Alkaline Solutions on Metals

A mechanism for enhancing the stability of the passive state of metals in silicate solutions is described on the basis of a study of the corrosion-electrochemical behavior of the metals in concentrated alkaline and silicate-alkaline solutions.     

Determination of five trace elements in sea water after separation by anion-exchange chromatography

Summary A preconcentration technique involving anion-exchange in a thiocyanate medium has been developed for the determination of traces of vanadium, cobalt, copper, zinc, and cadmium in sea water. A conventional, small column containing a strongly basic anionexchange resin Amberlite CG 400 in the thiocyanate form allows the five trace metals to be concentrated from a 11 of sea water sample adjusted to 0.1M in thiocyanate and 0.1M in hydrochloric acid. Sorbed metals can be recovered simultaneously by elution with 140 ml of 2M perchloric acid. A stepwise elution technique is also developed, which permits removal of vanadium-copper-cobalt as a group, zinc, and cadmium to improve the selectivity of the separation. A simple scheme of separation for vanadium, copper, and cobalt is given, so that spectrophotometric determinations of these metals even with nonselective reagents may be feasible. Results are quoted on the preconcentration and subsequent spectrophotometric determination of the five metals in brine and sea waters.     

X-ray determination of traces of hafnium in zirconium metal or traces of zirconium in hafnium metal after separation by ion exchange

A method is proposed for the determination of traces of hafnium in zirconium metal or zirconium in hafnium metal. The trace metals are first separated from the matrix metals on an ion-exchange column and then determined by X-ray analysis.     

贵金属组试剂聚硫醚吸附性能和应用的研究

我们合成了类似文献报道的聚硫醚(PTE)。通过各种性能实验,确定了试剂结构为HO CH_2—S CH_2OH,对Au、Pd、Pt、Rh、Ir、Ru、Os的吸附率在98％以上,且不吸附常见的非贵金属。分离富集效果优于文献。像PTE能吸附全部8个贵金属且饱和吸附容量非常大的吸着剂,尚属少见。     

Adventures with substances containing metals in negative oxidation states

A brief history of substances containing s,p- and d-block metals in negative oxidation states is described. A classification of these species and discussions of formal oxidation state assignments for low-valent transition metals in complexes are included, along with comments on the innocent and noninnocent character of ligands in metalates. Syntheses of highly reduced carbonyl complexes formally containing transition metals in their lowest known oxidation states of III- and IV- are discussed. Atmospheric-pressure syntheses of early-transition-metal carbonyls involving alkali-metal polyarene-mediated reductions of non-carbonyl precursors have been developed. In the absence of carbon monoxide, these reactions afford homoleptic polyarenemetalates, including the initial species containing three aromatic hydrocarbons bound to one metal. In several instances, these metalates function as useful synthons for "naked" spin-paired atomic anions of transition metals.