Bestimmung von Spurenelementen in Gewässern mittels Flotationsspektralphotometrie am Beispiel des Arsens

Highly sensitive and selective methods for the determination of trace elements in waters and solutions are made possible by the combination of flotation and spectrophotometry (flotation spectrophotometry). The basis for it are multiply charged anion complexes of the analyte, which form sparingly soluble ion association complexes with singly charged basic dye cations in aqueous solution. Intense shaking of the aqueous solution with an organic solvent (having a low dielectric constant) results in the accumulation of these ion association complexes at the interface or on the vessel walls (flotation step). After separating the ion association complexes from the liquid phases, they are dissolved and dissociated in a polar organic solvent and the absorbance of the basic dye ions is measured as a function of the concentration of the analyte. By the example of the trace determination of arsenic in natural water, the possibilities of analytical chemistry by combination of flotation steps and spectrophotometry are demonstrated. According to the arsenic content, its determination can be performed by flotation spectrophotometry with crystal violet (detection limit 50 ng/ml As), by an indirect determination of arsenic via flotation spectrophotometry of molybdenum in the dodecamolybdoarsenic acid (detection limit 1 ng/ml As) or by the combination of collector precipitation of arsenic with zirconium hydroxide followed by froth flotation and flotation spectrophotometry as the determination technique (detection limit 0.05 ng/ml As). The reproducibilities of these variants are indicated and their accuracy is checked by comparison of methods.     

Determination of Pesticides by HPLC Bestimmung von Pestiziden durch HPLC

Using solid phase extraction followed by HPLC, various pesticides of different chemical structure, thermolabile or polar components included, can be separated and quantitated chromatographically in a single run. Due to longer elution times compared to gas chromatography, only a limited number of components can be determined at the same time. According to our experience, all components relevant for a water catchment area can be covered. With the use of diode-array-detectors the identification of components can be done with sufficient security by comparison of spectra of reference sample and analytical peak. The determination limit is 0.025 μg/L with few exceptions.     

Use of Observations below Detection Limit for Model Calibration

Censored (nondetect) values occur when chemical concentrations in water samples are near or below the level that can be measured by an analysis method. It is common to either delete or substitute values for nondetect observations for use in model calibration, but this practice can bias the estimated parameter values and the model predictions. A more realistic representation of the system is obtained from the calibration if we include such observations in a manner reflecting that we know only the value is below the detection limit. Consequently, we propose use of the censored-residual approach to including nondetect values as observations for calibration. In this approach, residuals are calculated as the detection limit minus the simulated value when the simulated value exceeds the detection limit, and the residual is assigned a value of zero when the simulated value is below the detection limit. The new censored-residual approach is particularly advantageous when calibrating transport models to low concentration data.     

Voraussetzung und Grenzen der Qualitätssicherung in der Wasseranalytik

A discussion is presented on the conditions required and limitations of the guaranteeing of quality in water analysis as the basis for the necessary standardization of analytical methods. The following concepts are of particular importance: principle of analysis, method of analysis, technique of analysis, specification for analysis, measured value, analytical value, result of measurement, result of analysis, precision, repeatability, reproducibility, detection limit, determination limit, sensitivity and rate of retrieval. Prequisite for the ensuring of quality proper are the standard addition method and the ring analysis. In the water analysis the guaranteeing of quality is of particular importance due to the multifarious matrix as well as for the interpretation of the analytical results as a basis for important decisions in the national economy.     

核心型钢混凝土柱的轴压比限值试验研究

基于界限破坏时的内力平衡条件,推导了核心型钢混凝土柱轴压比限值的理论计算公式,计算分析了配钢率、混凝土强度等级、柱截面尺寸等因素对核心型钢混凝土柱轴压比限值的影响。进行了5个1/2比例模型柱试件的低周反复加载试验,验证了配置核心型钢对提高混凝土柱的抗震性能和轴压比限值的有效性。计算和试验结果表明,在混凝土柱中配置一定数量的核心型钢,可以有效提高轴压比限值。本文建议的方法可以较为合理地确定核心型钢混凝土柱的轴压比限值,供工程实践参考。     

Differential Pulse Polarographic Determination of the Oxime Carbamante Insecticide Alanycarb

As basis for the development of a sensitive analytical method for the determination of the insecticide alanycarb, a study of the differential pulse polarographic (DPP) reduction of alanycarb on a dropping mercury electrode (DME) was performed. The pesticide was found to give a single DP peak over the pH range 1.0 to 6.0 and the pH dependency of the peak potential showed a linear segment with a slope of 65.2 mV (at 20°C). For the analytical DPP method running at pH 6.0 (peak at –503.4 mV), the relationship between the peak current and alanycarb concentration was linear in the range of 1.10 to 9.76 μg mL^–1 with a detection limit of 0.33 μg mL^–1. The proposed method was applied for the determination of alanycarb in spiked dam water and orange juice samples. The recoveries calculated for both types of dam water and orange juice samples spiked with 12.0 μg mL^–1 alanycarb were 96.3 and 99.0% with relative standard deviations of 5.2 and 1.3%, respectively. The sufficiently good recoveries and low relative standard deviations for the data reflect the high accuracy and precision of the proposed differential pulse polarographic method. The effects of diverse metal ions and other commonly used pesticides on the determination of alanycarb were also investigated.     

Identifizierung ausgewählter Pestizide im Wasser mit Hilfe eines screening-Systems auf Grundlage der Dünnschichtchromatographie

After their extraction from water, 16 water pollutants of the families of triazines, urea herbicides, phenoxycarboxylic acids and organochlorine and organophosphorus insecticides are separated and identified by thin-layer chromatography. The method is suitable for routine analyses and was tested on model waters, inclusive of water from the Elbe river. The rate of redetection is up to 80%, the detection limit is at 0.5… 2 μg of the individual pollutants.     

Zur Bildung von Artefakten und deren Vermeidung bei der Bestimmung leichtflüchtiger Halogenkohlenwasserstoffe in Wasser mittels Headspace-Gaschromatographie unter den Bedingungen der DIN 38407 Teil 5 (DEV-F5). Teil II: Überhöhte Trihalogenmethanbefunde in gechlortem Schwimmbeckenwasser

Formation of Artefacts and its Suppression during the Determination of Volatile Halogenated Hydrocarbons in Water by Means of Headspace Gas Chromatography under the Standard Conditions of DIN 38407-F5. Part II: Increased Trihalomethane Formation in Chlorinated Swimming-pool Water A comparison of two analytical standard procedures for the determination of trihalomethanes (THM) in water (headspace gas chromatography and pentane extraction/gas chromatography) yielded strongly differing results. Under the conditions recommended by the German Standard Method DIN 38407-F5 (60…80°C for at least 60 min) degradation of thermo-labile chlorination products occurs resulting in elevated THM concentrations. The reactions involved are partly pH-dependant, and these can be suppressed by sample acidification. The degradation of trihalogen acetic acids, however, can only be influenced by minimizing the equilibration time and temperature. Other intermediate chlorination products (haloacetonitriles) are also degraded to THM after preceding hydrolysis to the corresponding carboxylic acids. Comparative results obtained with a purge and trap method at ambient temperature, i.e. without thermal stress during the enrichtment step, are lower than with static headspace GC but still high in comparison to the pentane extraction method. Presumably volatile THM-precursors are also trapped and subsequently decomposed upon thermal desorption from the trap. As the static headspace GC is the most rational method of LHKW determination available, the recommended experimental sample handling conditions should be modified in a way that deterioration reactions are reduced as far as possible.     

基于上限定理的软土隧道开挖面稳定性分析

应用极限分析上限法研究软土隧道开挖面的稳定性,提出了纯粘土地基中不排水条件下隧道开挖面稳定性问题的改进破坏模式,并推导了隧道开挖面稳定计算的理论公式;编制相应的计算程序,优化得到了维持开挖面稳定的支护压力最优上限解。通过与已有极限分析上限法和极限分析有限元上限解的对比,验证了本文改进破坏模式的有效性,为工程设计提供了可靠的理论依据。同时,将支护压力表示为土体粘聚力、地表超载和土体重度三相叠加的形式,给出了各自影响系数的表达式,并对之进行了分析讨论。     

Trace analysis of quaternary aminoalcohols as degradation products from softeners in wastewater

The sensitive and selective determination of polyalcohols without chromophores or fluorophores in the lower ppb-level is still an analytical task of high interest, especially in the field of environmental investigations. This paper describes a cation-exchange HPLC procedure for the separation and fluorescence detection of two quaternary ammonium compounds with polyalcoholic groups (degradation products of fabric softener) after derivatization with 9-fluorenylmethyl chloroformate (FMOC). Detailed experiments were carried out to determine optimum reaction conditions (pH, reaction time, temperature), linear range, detection limits, and kinetics of the reaction. The HPLC separation on a cation-exchange column includes a gradient program which provides complete separation from neutral compounds also reacting with FMOC and its hydrolysis products formed during the reaction in alkaline medium. High specificity for both investigated ammonium compounds with detection limits in the range of 1 ppb could be achieved.     

Determination of Cyanuric Acid in Swimming Pool Water and Milk by Differential Pulse Polarography

Cyanuric acid is a suspected gastrointestinal or liver toxicant in humans. Therefore, determination of trace cyanuric acid is very important, in this work a novel, sensitive, and reliable method was developed using differential pulse polarography. Optimum conditions for analytical determination were found to be at a pH of 9.5, Britton–Robinson at a reduction potential of ?105 mV. Experimental results indicate an excellent linear correlation between the peak current and the concentration in the range of cyanuric acid from 0.5 to 27.0 µM (0.06–3.5 µg mL^?1) with a correlation coefficient of 0.997. The limit of detection and limit of quantification were obtained as 0.15 and 0.5 µM (0.02–0.06 µg mL^?1), respectively. The proposed method was successfully applied to the determination of cyanuric acid in pool water and in spiked milk. Cyanuric acid level in swimming pool water was found as 2.54 ± 0.47 µg mL^?1 (19.7 ± 2.29 µM) in swimming pool water for N = 4 and 95% confidence interval. The recoveries were found to be sufficient. Also, the standard deviation of the data was low which shows high accuracy and precision of proposed differential pulse polarographic method. The influences of some other commonly found inorganic salts on the determination of cyanuric acid were also examined. Some interfering species were eliminated using complexing agents, e.g., EDTA.     

Large-scale pesticide monitoring across Great Barrier Reef catchments--Paddock to Reef Integrated Monitoring, Modelling and Reporting Program

The transport and potential toxicity of pesticides in Queensland (QLD) catchments from agricultural areas is a key concern for the Great Barrier Reef (GBR). In 2009, a pesticide monitoring program was established as part of the Australian and QLD Governments' Reef Plan (2009). Samples were collected at eight End of System sites (above the tidal zone) and three sub-catchment sites. At least two pesticides were detected at every site including insecticides, fungicides, herbicides, and the Reef Plan's (2009) five priority photosystem II (PSII) herbicides (diuron, atrazine, hexazinone, tebuthiuron and ametryn). Diuron, atrazine and metolachlor exceeded Australian and New Zealand water quality guideline trigger values (TVs) at eight sites. Accounting for PSII herbicide mixtures increased the estimated toxicity and led to larger exceedances of the TVs at more sites. This study demonstrates the widespread contamination of pesticides, particularly PSII herbicides, across the GBR catchment area which discharges to the GBR.     

Gaschromatographie zur Bestimmung von Pestiziden in aquatischen Systemen — Erfahrungen eines Landesuntersuchungsamtes Gas Chromatography for Determination of Pesticides in Aquatic Systems — Experience from a Governmental Laboratory

The applicability of gas chromatography for the determination of pesticides in aquatic systems is described. Potential and limitations of different methods for derivatization, chromatographic separation and detection are discussed. The analytical strategies for determination of pesticides with different chemical properties are given presenting examples from governmental laboratory analytical experience.     

Limit states and failure mechanisms of viscous dampers and the implications for large earthquakes

Fluid viscous dampers are used to control story drifts and member forces in structures during earthquake events. These elements provide satisfactory performance at the design‐level or maximum considered earthquake. However, buildings using fluid viscous dampers have not been subjected to very large earthquakes with intensities greater than the design and maximum considered events. Furthermore, an extensive database of viscous damper performance during large seismic events does not exist. To address these issues, a comprehensive analytical and experimental investigation was conducted to determine the performance of damped structures subjected to large earthquakes. A critical component of this research was the development and verification of a detailed viscous damper mathematical model that incorporates limit states. The development of this model and the laboratory and simulation results conclude good correlation with the new model and the damper limit states and provide superior results compared with the typical damper model when considering near collapse evaluation of structures. Copyright © 2010 John Wiley & Sons, Ltd.     

Gaschromatographische Spurenanalyse von leichtflüchtigen Halogenkohlenwasserstoffen in Wässern mittels simultaner ECD/FID-Detektion

The substances which are expulsed from the water sample by a nitrogen current are first adsorbed on a column filled with Tenax GC and subsequently expulsed at 200° and fed into the gas-chromatographic column. The parallel detection improves the identification of individual substances and makes the detection of aromatics possible at the same time. Characteristics of the process (detection limit, standard deviation, coefficient of variation, rate of retrieval) are determined and examples of analysis are given. For a water sample of 10 ml the detection limit lies at or below 1 μg/l.     

边坡稳定性分析及滑移面快速确定

针对边坡稳定性分析及滑移面确定这一工程问题,提出一种解析法。首先根据基本假设及边坡的几何关系,建立边坡滑移面确定模型,推导出滑移面控制方程;然后基于极限平衡理论,采用解析的方法推导出与滑移面控制方程相关联的安全系数解析表达式;最后通过求解目标函数（一元函数）在定义域上的最小值,求出边坡最小安全系数及对应的临界滑移面。通过算例验证表明：本文方法的边坡稳定性分析结果与传统极限平衡条分法分析结果基本一致,最小安全系数偏差不超过±5%;本文方法所确定的临界滑移面与基于传统极限平衡条分法所广泛搜索的临界滑移面比较接近。本文方法对于高效、精准地进行边坡稳定性分析及滑移面确定具有借鉴意义。     

Automated Ion-pair extraction and Ion-pair chromatography — a versatile method in water analysis for the determination of highly polar micropollutants

An automated HPLC method is presented which combines on-line ion-pair extraction on small exchangeable RP-C18 precolumns (RP-IPE) with ion-pair chromatography (RP-IPC). Weakly acidic herbicides — carboxylic acids, phenols, and the N-H acidic bentazone — and strong acids, e.g. aromatic sulfonic acids, can be determined simultaneously. Performance data are given. The tetrabutylammonium ion pairs of all investigated compounds are readily transferred from the RP-C18 precolumn to the analytical column by a phosphate buffer/methanol gradient. This is also true for the chlorinated phenoxy acids which, in earlier off-line extraction experiments, could not be desorbed from the RP-C18 material by the lower polar acetone. The RP-IPC is carried out at neutral pH where weakly acidic compounds appear in their stronger UV absorbing dissociated form. Compared to conventional reversed phase chromatography using an acidified eluent, the sensitivity of UV detection is markedly enhanced, especially for the phenol herbicides and bentazone. In addition, phenols can be detected more selectively because they show a second intense absorption band in the wavelength range between 280 nm and 290 nm, where there are only little interferences with the matrix. Due to miniaturization and automation, the online combination IPE/IPC allows a large sample throughput at a lower consumption of solid phase material and organic solvents. Time consuming manual steps are totally missing. The IPE/IPC technique is well suited as a screening method for fate studies of polar micropollutants, e. g. for monitoring the efficiency of different water treatment technologies. An example for balancing an activated carbon filter is presented.     

Determination of Irgarol-1051 and its related s-triazine species in coastal sediments and mussel tissues by HPLC-ESI-MS/MS

A mild, low-temperature analytical approach based on sonication assisted extraction coupled with HPLC electrospray ionization triple quadrupole tandem mass spectrometry has been developed for the simultaneous qualitative and quantitative determination of the four Irgarol-related s-triazine species, namely Irgarol-1051, M1, M2 and M3, in coastal sediments and Green-lipped mussel samples. Mild extraction conditions were necessary for the preservation of the thermally unstable M2. The Multiple Reaction Monitoring (MRM) mode of detection by ESI-MS/MS enabled reliable qualitative identification and sensitive quantitative determination of those s-triazines. This determination method was applied to evaluate the degree of Irgarol-1051 contamination in the sediments and biota of the coastal environment of Hong Kong - one of the busiest maritime ports in the world. All the four s-triazine species were observed in all of the samples. This is the first time that the newly identified M2 and M3 are detected in coastal sediments and biota tissues.     

Neues mathematisches Verfahren zur Charakterisierung unbekannter organischer Vielstoffgemische durch die Adsorptionsanalyse

The adsorption analysis, a process-technology-oriented analytical method, characterizes complex organic multicomponent mixtures with respect to their different adsorbability by a sorbent such as activated carbon. The analytical method is based on the determination of adsorption isotherms and their mathematical interpretation. So far, this interpretation has required the use of a large computer or a time-consuming computing program, in general. With the BASIC computing program “MAVIAS 10”, on the basis of the IAS theory a mathematical approach has been found which provides sufficient accuracy, demands low expenditure of time and makes the use of a small computer possible.