Determination of thorium isotopes in gas lantern mantles by alpha-spectrometry

A procedure for the determination of the three main isotopes of thorium in gas lantern mantles by alpha-spectrometry has been developed. The samples examined were dissolved in concentrated nitric acid and thorium was precipitated as hydroxide. Thorium was then dissolved in hydrochloric acid to be extracted into a TOPO solution, back-extracted with sulfuric acid, electrodeposited onto a steel disc and finally counted alpha-spectrometrically. The radiochemical recovery for thorium was 94% with a counting efficiency of 37%.     

Separate vaporisation of boric acid and inorganic boron from tungsten sample cuvette-tungsten boat furnace followed by the detection of boron species by inductively coupled plasma mass spectrometry and atomic emission spectrometry (ICP-MS and ICP-AES)

Utilising extremely different vaporisation properties of boron compounds, the determination procedures of volatile boric acid and total boron using tungsten boat furnace (TBF) ICP-MS and TBF-ICP-AES have been investigated. For the determination of volatile boric acid by TBF-ICP-MS, tetramethylammonium hydroxide (TMAH, Me₄NOH) was used as a chemical modifier to retain it during drying and ashing stages. As for the total boron, not only non-volatile inorganic boron such as boron nitride (BN), boron carbide (B₄C), etc. but also boric acid (B(OH)₃) was decomposed by a furnace-fusion digestion with NaOH to produce sodium salt of boron, a suitable species for the electrothermal vaporisation (ETV) procedure. The proposed method was applied to the analysis of various standard reference materials. The analytical results for various biological and steel samples are described.     

Determination of237Np in large volume samples of sea water by a radiochemical procedure

A radiochemical procedure followed by alpha spectrometry has been developed for the determination of²³⁷Np present at low activity concentrations in seawater. The analytical procedure is based on concentration of actinides from 1800 1 sea water samples by hydroxide precipitations. Neptunium is isolated by ion exchange, fluoride precipitation and extraction with TTA (thenoyltrifluoroacetone). As a radiochemical yield determinant²³⁹Np or²³⁵Np is used. Neptunium is electroplated onto stainless steel discs before alpha-spectrometry for about 10 days. The procedure allows for sequential separation of plutonium, americium, technetium and radiocaesium together with neptunium. The radiochemical yield for neptunium is only 20–50%, but the procedure has been applied with success on several samples contaminated with²³⁷Np at fallout or close to fallout levels.     

Polarographic determination of malononitrile

A procedure is proposed for the determination of malononitrile by differential pulse polarography in methanolic 0.1M tetraethylammonium iodide/0.001M tetramethylammonium hydroxide as the supporting electrolyte. In this medium malononitrile is chemically converted into an electroactive species. With close control of timing of the steps in the procedure the error of the method is +/-1.5% in the concentration range 0.0001-0.001M. Acrylonitrile, benzonitrile and succinic acid dinitrile do not interfere.     

A novel method for the preparation of thin dense Pd membrane on macroporous stainless steel tube filter

Thin Pd membranes were in situ deposited on macroporous stainless steel (MPSS) tubes using an improved electroless plating method consisting of material filling in the substrate pores, Pd plating on the filled substrate, and recovery and activation of the substrate pores. The Pd/MPSS composite membranes resulted from the filling materials of both aluminum hydroxide gel and Pd/aluminum hydroxide gel have been studied in detail and compared with each other. The hydrogen permeation mechanism through both membranes may be controlled by surface reactions, while the hydrogen permeation flux and activation energy for the membrane resulted from Pd/aluminum hydroxide gel are higher than these for the membrane resulted from aluminum hydroxide gel. In the case of the former membrane, which is almost pinhole free, the hydrogen permeation flux is as high as 0.302 mol/(m² s) with a pressure difference of 100 kPa at 773 K. Good membrane stability is also proven by the unchanged membrane surface morphology, the steady hydrogen permeance, and the complete hydrogen selectivity. The deposition mechanism of the membrane has been proposed and interpreted in detail.     

A simple method for the alkaline hydrolysis of esters

A very mild and rapid procedure for the efficient alkaline hydrolysis of esters in non-aqueous conditions has been developed, by the use of dichloromethane/methanol (9:1) as solvent. This method conveniently provides both carboxylic acids and alcohols from the corresponding esters and sodium hydroxide in a few minutes at room temperature. A plausible reaction mechanism is proposed.     

Analysis of silica fume produced by zircon desilication

Novel chemical methods have been developed to allow for the determination of the components of silica fume produced by zircon desilication. Hitherto, no methods have been described for the analysis of this material. The amorphous silica is first removed by treatment with sodium hydroxide. The residue from the hydroxide treatment may then be subjected to a suite of reagents to determine the zircon, the total zirconia, the monoclinic zirconia and the tetragonal zirconia content of the fume. The zircon content of the fume is determined by treatment of the hydroxide residue with concentrated hydrofluoric acid (HF). The total zirconia content of the fume is determined by digestion of the hydroxide residue with fuming sulphuric acid (oleum), while the relative amounts of monoclinic and tetragonal zirconia may be found by treatment of the hydroxide residue with 10%w/v HF, which attacks the less stable tetragonal phase. Both X-ray diffraction and particle size analysis were used to validate the steps in the analytical procedure. An explanation of the presence of tetragonal zirconia in the fume is proposed. A greater understanding of the composition of the fume led to the installation of a separator in the company's production line to remove the zircon. Australian Fused Materials (AFM) now produces a vastly superior grade of fume marketed under the code SF-98.     

Analytik der polyacrylnitrilfasern : V über fine abgewandete reduktionsmethode zur bestimmung geringer schwefelmengen in acrylnitrilpolymerisaten

Sulphur contents (0.01–0.2% S) in polyacrylonitriles (50–100 mg samples) can be estimated by decomposition of the polymer by heating with KOH, reduction of the sulphate formed (with acetic acid, hydriodie acid, and hypophosphite) and absorption of hydrogen sulphide in 1 N sodium hydroxide. Sulphide is then determined polarographically utilizing the anodic sulphide wave, or potentiometrically with 0.001 M mercuric chloride as titrant and amalgamated silver wire and stainless steel wire as electrodes. The whole procedure is done easily in a stream of nitrogen and can therefore be applied even when the atmosphere is contaminated with sulphur-containing substances.     

基准邻苯二甲酸氢钾标定NaOH标准溶液的不确定度评定

对实验室自配的1 mol/L NaOH标准滴定溶液的浓度进行不确定度评定,建立不确定度评定程序和方法,并依据GB/T601-2002建立数学模型.确定了影响NaOH标准滴定溶液浓度的主要因素,归纳了不确定度的主要来源,建立了用基准试剂标定标准滴定溶液浓度的不确定度评定程序和方法.当NaOH标准滴定溶液浓度为1.0201 mol/L时,扩展不确定度为0.0040 mol/L.该程序和方法适用于同类型实验的不确定度评定.     

Extraction and determination of hexavalent chromium in soil samples

A procedure for the extraction of Cr(VI) from solid soil-like samples was presented in which the complexing properties of diethylenetriaminepentaacetic acid (DTPA) were exploited to extract insoluble compounds of Cr(VI). A concentration of DTPA in an ammonium sulphate/ammonium hydroxide buffer equal to 0.02 mol l⁻¹ was chosen. The conditions of extraction of insoluble Cr(VI) from solid samples were optimised using soil certified reference material spiked with known concentration of insoluble Cr(VI) added as PbCrO₄. The extracts were analysed by adsorptive stripping voltammetry. Validation of the proposed procedure of extraction was carried out by analysis of certified reference material (CRM) 545 and comparison of the results obtained using the proposed and other methods of extraction in the course of analysis of natural soil samples.     

Synthesis and Reactivity of 3-R-1-Adamantyl Methyl Ketones

A general procedure was proposed for synthesizing 3-R-1-adamantyl methyl ketones from the corresponding adamantanecarbonyl chlorides and dimethyl malonate in toluene (benzene) in the presence of sodium hydroxide. Intermediate dimethyl (3-R-1-adamantylcarbonyl)malonates can also be isolated. The resulting ketones were brought into reactions with hydroxylamine and formamide in the presence of formic acid to obtain the corresponding oximes and 1-(3-R-1-adamantyl)ethylamines. Dimethyl (3-R-1-adamantyl- carbonyl)malonates reacted with phenylhydrazine to give adamantyl-substituted 4,5-dihydropyrazol-5-one derivatives.     

Alkyl 3-nitroacrylates: Synthesis and reactions with cyclohexane-1,3-diones and Meldrum’s acid

A modified procedure was proposed for the synthesis of alkyl 3-nitroacrylates by nitroiodination of alkyl acrylates and subsequent dehydroiodination of iodonitropropanoates with triethylamine. Alkyl 3-nitroacrylates reacted with cyclohexane-1,3-dione, dimedone, and Meldrum’s acid in the presence of N,N,N-tri-methylanilinium hydroxide (Rodionov’s catalyst) in anhydrous methanol to give the corresponding Michael adducts.     

Periodate oxidation analysis of carbohydrates : Part I. Spectrophotometr1c determination of glyoxal in dialdehyde fragments formed from glycosides with 2,4-dinitrophenylhydrazine

A simple procedure for the determination of glyoxal in dialdehyde fragments, formed from glycosides by periodate oxidation, is proposed. By heating sample solutions prepared by dilution of reaction mixtures for periodate oxidation, with an aqueous dimethylsulfoxide solution of 2,4-dinitrophenylhydrazine hydrochloride. followed by addition of an aqueous ethanolic solution of potassium hydroxide, intense color with an absorption maximum at 576 nm developed. The spectrophotoinetric method based on this color reaction makes it possible to determine selectively 1·10^?2–2·10^?1 μmole amounts of conjugated glyoxal without a prior liberation process. Data for glyoxal content obtained by this procedure are discussed in relation to overoxidation.     

Spectrophotometric determination of copper in alkaline solutions and evaluation of some hydroxy-substituted 1,10-phenanthrolines as chromogenic reagents

Seven new hydroxy-substituted 1,10-phenanthroline derivatives have been evaluated as chromogenic reagents for the determination of copper in strongly alkaline solution. The most sensitive of these, 2,9-dimethyl-4,7-dihydroxy-1,10-phenanthroline, has proven to be highly effective in a simple, rapid procedure for determining trace amounts of copper in sodium hydroxide, potassium carbonate, sodium phosphate or ammonium hydroxide.     

硅钙合金中非合金相态硅的分析

硅钙合金是一种炼钢脱氧剂,其中若存在游离硅、二氧化硅杂质会影响炼钢脱氧效果,目前国家标准无硅钙合金中游离硅分析方法。研究了氢氧化钠溶液提取非合金相硅的条件,用硅钼蓝光度法分析硅含量,分析方法回收率达95.9%,可用于硅钙合金中非合金相硅测定。     

Uranium association with corroding carbon steel surfaces

We investigated the association of uranium with clean and corroded surfaces of 1010 carbon steel. Studying steel contaminated by uranium species will have an important effect on the development of methods used to clean radioactively contaminated metal waste. X‐ray photoelectron spectroscopy, synchrotron infrared microspectroscopy and laboratory‐based Fourier transform infrared analysis of steel surfaces exposed to uranyl nitrate showed the presence of crystallized hydrated uranyl oxides, uranyl hydroxides, iron oxyhydroxides and iron oxides. In general, heavily corroded areas physically shield the uranium species, which tended to associate spatially with hydroxyl groups and lepidocrocite. Lightly corroded areas contained uranium species with stronger axial U–O bonding. Infrared spectroscopy, Rutherford backscattering spectroscopy and energy‐dispersive spectroscopy mapping analysis revealed that the uranium species are well distributed within the upper micron of the thick corrosion layer and associated more with areas of high hydroxide content. Parameters such as the concentration of uranyl nitrate solution used to expose the carbon steel coupons, the method of contamination (dipped or sprayed with dilute uranyl nitrate solution) and the degree of corrosion (accelerated corrosion before and/or after contamination) played significant roles in the distribution and nature of the uranyl hydroxide/iron oxyhydroxide corrosion products found on the surface of all coupons. These factors must be considered in the development and optimization of decontamination processes for metal waste. Copyright © 2003 John Wiley & Sons, Ltd.     

Influence of the Composition of Chloride-containing Solutions on the Corrosion of 12Cr18Ni10Ti Steel

The corrosion activity of chloride-containing solutions formed in production of ternary nitrogen-phosphorus-potassium fertilizers was studied. The inhibiting effect of hydroxide ions on the corrosion of 12Cr18Ni10Ti steel during the evaporation of solutions of nitrogen-phosphorus-potassium fertilizers was evaluated.     

Automatic flow system titration based on multicommutation for spectrophotometric determination of total acidity in silage extracts

A multicommutated flow titration procedure is proposed for the spectrophotometric determination of total acidity in silage extracts. The flow network comprises a set of 3-way solenoid valves, computer-controlled to provide facilities to handle the titrand, titrant, and carrier solutions by using a single pumping channel. The procedure is based on the volumetric fraction variation approach that maintains the same volume of titrand solution and varies the titrant solution step by step, to provide determination without the use of an analytical curve. The procedure is implemented by using phenolphthalein as an external indicator; the proposed algorithm was able to titrate silage extracts presenting different color intensities. Sample solutions with concentrations ranging from 10(-3) to 10(-1) mol/L total acidity could be analyzed by using 10(-2) mol/L sodium hydroxide as the titrant solution. Other advantages include a relative standard deviation of <1.0% (n = 4) for a typical silage extract solution containing 26 mmol/L total acidity; an analytical throughput of 16 determinations per hour was also achieved. Accuracy was assessed by processing a set of silage extract solutions and comparing the results with those obtained by using the conventional potentiometric titration procedure. No significant difference at the 95% confidence level was observed.     

Fluorometric determination of carbaryl in micellar Media

A new method is proposed for the fluorometric determination of carbaryl, based on the basic hydrolysis of the pesticide to 1-naphtholate at pH 12 and enhancement of the relative quantum yield of this latter compound by the presence of non-ionic surfactants. The procedure is quick and easy and presents a limit of detection of 1.4 ng/ml. The interaction of carbaryl with non-ionic surfactants has been studied both spectrophotometrically and fluorometrically, in different media. To determine carbaryl in real samples prior extraction into xylene and back-extraction with 1 M sodium hydroxide is necessary to avoid the strong quenching effect of the matrix.     

Rapid and simple clean-up and derivatization procedure for the gas chromatographic determination of acidic drugs in plasma

A rapid and simple clean-up and derivatization procedure that can be generally applied to the gas chromatographic (GC) determination of acidic drugs of various chemical and therapeutic classes is described. The drugs are extracted from acidified plasma with chloroform containing 5% of isopropanol, which is then evaporated. The residue is dissolved in toluene, then the drugs are back-extracted into a small volume of a methanolic tetramethylammonium hydroxide solution. The solution obtained is added to N,N-dimethylacetamide and the drugs are treated with n-butyl iodide and chromatographed as their n-butyl esters. Retention times are given for three different columns; the results show that in all but three instances one derivative is formed. The recoveries in the extraction steps were determined by GC and UV spectrophotometry. The recovery of the back-extraction and of the extraction from plasma with chloroform-isopropanol is fairly good. For some drugs toluene can be used as the extraction solvent, which has the advantage that no evaporation of the extract is necessary, and it can be extracted directly with the tetramethylammonium hydroxide solution. Chromatograms of blank plasma treated according to the described procedure do not show interfering peaks from endogenous compounds. The advantages of the proposed method are as follows. It is a standard procedure that can be used for different types of drugs, using one standard column, with no interference from endogenous compounds. Separation is achieved between drugs that differ only in the number or position of the methyl groups and between a drug and its demethylated metabolite(s). No decomposition of the products occurs during the alkylation process and injection of the resulting neutral solution is not detrimental to the column material.