Compression stress relaxation

The requirements of apparatus to measure stress relaxation of rubbers in compression are outlined. Apparatus available commercially are described, in particular a universal semi-automatic force measuring head and jigs which accept button test pieces and have no sliding bearings to introduce friction.     

Application of arsenic to electrophotoreceptors

Arsenic has been applied to many electronic devices such as electrophotoreceptors, gallium arsenide (GaAs) semiconductors and solid-state image pickup devices. For electrophotoreceptors selenium–arsenic (Se? As) alloys are coated onto the conductive substrate of the receptors. Arsenic is mostly used in electophotoreceptors in electronic devices. During the coating process, a part of the gaseous arsenic is released through an exhaust system. In order to avoid arsenic being discharged to the atmosphere, bag filters and high-efficiency particulate air filters are set before the exhaust port. Any arsenic which still exists in the waste water after washing tools and jigs from the coating process is collected by sedimentation before discharging. The Ames salmonella/microsome plate test for As₂Se₃ indicated no mutagenic activity under the test system used. For the safety of workers engaged in arsenic-related jobs, they received a medical examination once every six months. No negative trends from the examination was found in 428 men who received the examination from Autumn 1980 to Spring 1987.     

A study of a high repetition condensed arc source for the analysis of low alloy steels using different counter electrode sample configurations: II. A comparison between flat and dimple samples using a tungsten pin counter electrode

A high repetition condensed arc source was further investigated as a light source for the analysis of low alloy steel samples using a tungsten pin counter electrode. Experiments using different tangential and axial flow configurations as well as with only an axial flow, and using manganese as test element are described. With long pre-arc times necessary for sequential spectrometers, a build-up of material on the counter electrodes of different diameters occurred. To overcome this problem the use of counter electrodes with a fresh ground surface for every exposure was investigated. Modifications of the counter electrode holder and the necessary tools and jigs to achieve the effective change of the counter electrodes between exposures is described. Assessment of the performances of the different counter electrode sample configurations with various gas flows indicated that the use of only a tangential flow appears to be the preferred condition. The effect of relatively high phosphorous concentrations on the reproducibility of the analytical results for manganese is indicated. Burn patterns and sample build-up on the counter electrodes are discussed.     

机械润滑油中含水量的高速分析

因生产现场需要，试验在参照国外气量法快速测定润滑油含水量的基础上，用自制的设备进行试验，成功地摸索出一种高速分析方法，整个反应过程中在３ｍｉｎ２０ｓ内结束。通过对含水量压力之间相互关系的回归分析，得到几种机械润滑油可共同适用的回归方程，总结出温度变化对试验结果的影响，并通过与蒸馏法的平行比较，验证了方法的先进和可行笥。     

Development of a microparticle-based on-site immunoassay for the detection of atrazine in soil and water samples

Atrazine is widely used as a herbicide in agriculture and has been identified as a major groundwater contaminant in the US. Because of the possible hazard associated with its usage, there is a need for an efficient and economic screening method for on-site field testing of atrazine and other s-triazine herbicides in soil and water. We have developed a rapid, on-site test for the detection of atrazine based on the principle of microparticle agglutination inhibition immunoassay. The test detects 50 microg kg(-1) (0.050 ppm) atrazine in soil samples with direct extraction and 1.0 microg L(-1) atrazine in water samples when coupled with solid phase extraction.     

环境水质中酚类优先监测物的气相色谱法测定

以气相色谱法（ＧＣ）测定了环境水质中的重点酚类污染物。选择乙酸酐作衍生化试剂、甲苯为萃取剂,比较了不同的衍生ｐＨ条件,给出了氢火焰离子化检测器（ＦＩＤ）分离测定酚类污染物的精密度和检出限。方法简便实用,经５家实验室验证表明：适用于监测地表水和污水中的酚类物质。６种酚类优先监测物的检测限为０．６～７μｇ／Ｌ。     

Simulation of liquid water using semiempirical Hamiltonians and the divide and conquer approach

This work examines the ability of semiempirical methods to describe the structure of liquid water. Particularly, the standard AM1 and PM3 methods together with recently developed PM3-PIF and PM3-MAIS parametrizations have been considered. We perform molecular dynamics simulations for a system consisting of 64 or 216 water molecules in a periodic cubic box. The whole system is described quantum mechanically. Calculations with 64 molecules have been carried out using standard SCF techniques whereas calculations with 216 molecules have been done using the divide and conquer approach. This method has also been used in one simulation case with 64 molecules for test purposes. Within this scope, the molecular dynamics program ROAR have been coupled with a linear scaling semiempirical code (DivCon) implemented in a parallel MPI version. The predicted liquid water structure using either AM1 or PM3 is shown to be very poor due to well-known limitations of these methods describing hydrogen bonds. In contrast, PM3-PIF and PM3-MAIS calculations lead to results in reasonably good agreement with experimental data. The best results for the heat of vaporization are obtained with the PM3-PIF method. The average induced dipole moment of the water molecule in the liquid is underestimated by all semiempirical techniques, which seems to be related to the NDDO approximation and to the use of minimal basis sets. A brief discussion on charge-transfer effects in liquid water is also presented.     

塞曼火焰原子吸收法测定黄河水体的总硬度

采用原子吸收分光光度法测定黄河水体的总硬度,钙的浓度在0.100～5.00 mg/L、镁的浓度在0.0500～2.00 mg/L范围内分别与吸光度呈线性关系,线性方程分别为A=0.045 5c+8.354×10~(-5)、A=0.514c+8.354×10~(-5),相关系数均为0.9999。黄河水样6次测定结果的相对标准偏差为1.2％,t检验结果表明,该法与EDTA络合滴定法测定结果无显著性差异。     

Evaluation,Pitfalls and Recommendations for the “Water Layer Test” for Solid Contact Ion‐selective Electrodes

The “water layer test” is a crucial validation step of solid‐contact ion‐selective electrodes. It can confirm or contest the claim that the tested electrode is indeed a genuine solid contact electrode without an aqueous film between the ion‐selective membrane and its solid contact. Information about the presence of a water layer is essential for the interpretation of drifts in the electrode potentials commonly experienced with solid contact electrodes. Since its publication, the water layer test has been ubiquitously used, but without a standardized protocol the interpretation (or misinterpretation) of the test results led to uncertainties in the conclusions. Through both experiments and simulations based on theoretical models we have investigated the experimental parameters that can influence the results of the water layer test. We propose guidelines to minimize the possibility of misinterpretation of the results of the water layer test by considering the key factors that affect the shape of transients recorded during the water layer test. Most importantly, we emphasize the importance of allowing sufficient time for conditioning the tested electrode before the water layer test and providing adequate time for equilibration during the experiment. Using a thin ion‐selective membrane and thin solid‐contact layer for the tests is also recommended.     

Development of a novel ultrasound-assisted surfactant-enhanced emulsification microextraction method and its application to the analysis of eleven polycyclic aromatic hydrocarbons at trace levels in water

A novel ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) technique has been proposed by using low-density extraction solvents. In the proposed technique, Tween 80 and cyclohexane were injected into 5-mL glass test tubes with conical bottoms, containing 5.00 mL of a water sample that was located inside the ultrasonic bath. When the extraction process was finished, the glass test tube was sealed with a rubber plug and then placed upside down in a centrifuge. The finely dispersed droplets of cyclohexane collected at the conical bottom of test tube because the density of cyclohexane is less than of water, and the PAHs were concentrated in the cyclohexane. Next, 5 μL of the cyclohexane that collected at the conical bottom was removed using a 10-μL microsyringe and injected into high performance liquid chromatography coupled with fluorescence detection (HPLC-FLD) for analysis. The proposed method avoided the use of chlorinated solvents, which have been widely used as extraction solvents in a normal UASEME assay. Parameters that affected the extraction efficiency, such as the type and volume of the extraction solvent, the type and concentration of the surfactant, and the ultrasound emulsification time and salt addition, were investigated and optimised for the method. Under the optimum conditions, the enrichment factors ranged between 90 and 247. The limits of detection of the method were 0.6-62.5 ng L(-1). Good recoveries and repeatability of the method for the eleven PAHs were also obtained. The proposed UASEME technique has been demonstrated to be simple, practical and environmentally friendly for the determination of PAH residues in real water samples.     

Interlaboratory assessment of measurement precision and bias in the coulometric Karl Fischer determination of water

The precision and bias of the coulometric Karl Fischer ASTM method D1533-00 have been assessed in a collaborative ASTM round robin program for a group of 34 laboratories. The test materials used in this study included water saturated 1-octanol (WSO), water saturated 1-butanol (WSB), and a series of new and used transformer oil samples. Fundamental systematic biases have been demonstrated in the accuracy of the measurement of water in the WSO, WSB, and transformer oil samples. The systematic bias in the measurement of the WSO and WSB standards indicates that for some laboratories either the instruments were not accurate or the quantity of the standard was not measured accurately. A second type of systematic bias consisted of measurement errors associated with the selection of the Karl Fischer solvent that was used with each instrument, and this was superimposed upon the error in the measurement of the water in the standards. Using the statistical calculation method ASTM D 6300 the repeatability and reproducibility for water in transformer oil were found to be 7 mg/kg and 14 mg/kg respectively. The method detection limit of water was 8 mg/kg oil. The method bias was estimated based on the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 2890, WSO, since no suitable reference material for water in transformer oil was available for this study.     

Quantitative GC determination of water in small samples

Summary A gas chromatographic method with thermal conductivity detector (TCD) was developed for the determination of water in small amounts (2mg–20 mg) of solid chemicals. Quantification of water is carried out by using ethanol as an internal standard. The method shows good linearity in the range 0.1%–10% water. The precision as repeatability tested with a sample containing 0.5% water has a coefficient of variation of 5.3%. Comparison of the GC test results with another independent method (Karl-Fischer-titration) confirms the accuracy of the new method. Easy handling, independence of the chemical structure of the test substance and the small amount of sample needed are the major advantages of this alternative method of determining the water content of solid chemicals.     

基于媒介体的电化学水体总毒性检测方法现状及展望

基于媒介体的电化学水体总毒性检测方法是一种灵敏、可靠的水体总毒性检测方法。 它以原位培养微生物为毒性检测受试体,能够更加准确的反映目标水体的水体总毒性变化,因此适合用于水体复合污染的评估及水质安全预警。 本文从检测原理、媒介体、微生物等方面详细阐述了该方法的研究现状,并对该方法今后的发展方向进行了展望。     

Detection of exhausted coffee in genuine roasted coffee and estimation of the added amount

A method for the detection and estimation of the percentage of exhausted coffee admixed to genuine coffee is presented. The method is based on a fluorescence spot test obtained on water extraction of the tested substance spread on filter paper. The use of the proposed test for general examination of coffee purity is discussed.     

Stable Carbon Isotope Analysis of Hexachlorocyclohexanes by Liquid–Liquid Extraction Gas Chromatography Isotope Ratio Mass Spectrometry: Method Evaluation and Applications

Compound specific isotope analysis (CSIA) and enantiomer specific isotope analysis (ESIA) are powerful tools for assessing the fate of hexachlorocyclohexanes (HCHs) in the environment. However, there is no systematic study on the CSIA and ESIA analysis test methods of the carbon isotopes of HCHs in water and soil environments, in particular the isotope fractionation in the pre-concentration process. We endeavored to test the compatibility of CSIA and ESIA with the liquid–liquid extraction method of HCHs in water. The results showed that there were negligible changes in the δ¹³C of HCHs after extraction, indicating that liquid–liquid extraction can be used as a pre-concentration method for the determination of δ¹³C of HCHs in water. The optimized method was validated and then applied to differentiate three HCHs from different manufacturers, to identify in situ degradation of HCHs of groundwater from a contaminated site and to resolve the carbon isotope fractionation occurring in the α-HCH oxidation by CaO₂/Fe(II) Fenton system. The results showed that the same reagents from different manufacturers have different carbon isotope compositions, and different isomers from the same manufacturer also have different isotope compositions, showing useful evidence in identifying the source of HCHs. The more enriched δ¹³C in the down-gradient wells indicated that HCHs have undergone biodegradation or/and chemical reactions in the groundwater system of the site. Carbon isotopic enrichment factors (ε_C) of −1.90 ± 0.10‰ were obtained in the oxidation process. Hence, the method validated in this study has great potential as a method for identifying the degradation of HCHs in a water environment.     

An interlaboratory comparison on whole water samples

The European Water Framework Directive 2000/60/EC requires monitoring of organic priority pollutants in so-called whole water samples, i.e. in aqueous non-filtered samples that contain natural colloidal and suspended particulate matter. Colloids and suspended particles in the liquid phase constitute a challenge for sample homogeneity and stability. Within the joint research project ENV08 “Traceable measurements for monitoring critical pollutants under the European Water Framework Directive 2000/60/EC”, whole water test materials were developed by spiking defined amounts of aqueous slurries of ultra-finely milled contaminated soil or sediment and aqueous solutions of humic acid into a natural mineral water matrix. This paper presents the results of an European-wide interlaboratory comparison (ILC) using this type of test materials. Target analytes were tributyltin, polybrominated diphenyl ethers and polycyclic aromatic hydrocarbons in the ng/L concentration range. Results of the ILC indicate that the produced materials are sufficiently homogeneous and stable to serve as samples for, e.g. proficiency testing or method validation. To our knowledge, this is the first time that ready-to-use water materials with a defined amount of suspended particulate and colloidal matter have been applied as test samples in an interlaboratory exercise. These samples meet the requirements of the European Water Framework Directive. Previous proficiency testing schemes mainly employed filtered water samples fortified with a spike of the target analyte in a water-miscible organic solvent.     

Reduction of matrix effects and improvement of sensitivity during determination of two chloridazon degradation products in aqueous matrices by using UPLC-ESI-MS/MS

The development and validation of a sensitive and reliable detection method for the determination of two polar degradation products, desphenyl-chloridazon (DPC) and methyl-desphenyl-chloridazon (MDPC) in surface water, ground water and drinking water is presented. The method is based on direct large volume injection ultra-performance liquid chromatography electrospray tandem mass spectrometry. This simple but powerful analytical method for polar substances in the aquatic environment is usually hampered by varying matrix effects, depending on the nature of different water bodies. For the two examined degradation products, the matrix effects are particularly strong compared with other polar degradation products of pesticides. Therefore, matrix effects were studied thoroughly with the aim of minimising them and improving sensitivity during determination by postcolumn addition of ammonia solution as a modifier. An internal standard was used in order to compensate for remaining matrix effects. The calibration curve shows very good coefficients of correlation (0.9994 for DPC and 0.9999 for MDPC). Intraday precision values were lower than 5 % for DPC, 3 % for MDPC and the limits of detection were 10 ng/L for both substances. The method was successfully used in a national round robin test with a deviation between 3 and 8 % from target values. Finally, about 1,000 samples from different water bodies have been examined with this method in the Rhine and Ruhr region of North-Rhine-Westphalia (Germany) and in the European Union. Approximately 76 % of analysed samples contained measurable amounts of DPC at concentrations up to 8 μg/L while 53 % of the samples showed MDPC concentrations up to 2.3 μg/L.     

Multivariate calibration applied to simultaneous chemiluminescence determination of cobalt and chromium

The simultaneous determination of chromium and cobalt in water samples has been studied. Chemiluminescence registers based on the luminol-hydrogen peroxide reaction have obtained by a batch procedure. PLS algorithms have employed to model the time-response (formation and destruction of emitter).The influence of the presence of two metals and the non-linearity relationship between response and concentration have been evaluated in the signal. Different experimental designs and the selection of variables have been tested. The calibration set has been selected based on two criteria: unicomponent and/or bicomponent standard solutions and the slope calculated from linear univariate calibration. The response has been modelled providing high percentages of explained variance, robust models and low prediction errors.The proposed methodology has been validated using test standard solutions and a standard reference material of fresh water. Accurate results have proved the advantages of this method for the simultaneous determination of chromium and cobalt in water samples.