Development of a screening method for the analysis of organic pollutants in water using dual stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry.

The development of a method for screening of organic compounds with a wide range of physico-chemical properties in water, based on dual stir bar sorptive extraction coupled with thermal desorption and gas chromatography-mass spectrometry (dual SBSE-TD-GC-MS) is described. The investigated water sample is divided into two aliquots and extracted with stir bar sorptive extraction at two different conditions: using addition of methanol or sodium chloride, respectively. Following extraction, the two stir bars are inserted into the same glass thermal desorption liner and are simultaneously desorbed and analysed by GC-MS. The method optimisation was performed using 45 environmentally harmful substances with different volatilities (boiling point from 193 to 495°C), polarity (logK(ow) from 2.17 to 8.54) and acido-basic properties. The majority of model compounds was selected from the EU list of priority substances in the field of water policy and from the US EPA method 625, respectively. Optimisation was performed for extraction parameters (sample volume, extraction time, stirring rate, addition of modifiers) as well as for the thermal desorption conditions (desorption flow, desorption time, cryofocusing temperature). Performance characteristics (recovery, repeatability, carryover, linearity, limits of detection and quantification) were determined for the optimised method. An example of analysis of a contaminated groundwater sample is presented.

Effect of soil and sediment composition on acetochlor sorption and desorption.

BACKGROUND, AIM, AND SCOPE: Herbicide fate and its transport in soils and sediments greatly depend upon sorption-desorption processes. Quantitative determination of herbicide sorption-desorption is therefore essential for both the understanding of transport and the sorption equilibrium in the soil/sediment-water system; and it is also an important parameter for predicting herbicide fate using mathematical simulation models. The total soil/sediment organic carbon content and its qualitative characteristics are the most important factors affecting sorption-desorption of herbicides in soil or sediment. Since the acetochlor is one of the most frequently used herbicides in Slovakia to control annual grasses and certain annual broad-leaved weeds in maize and potatoes, and posses various negative health effects on human beings, our aim in this study was to investigate acetochlor sorption and desorption in various soil/sediment samples from Slovakia. The main soil/sediment characteristics governing acetochlor sorption-desorption were also identified. MATERIALS AND METHODS: The sorption-desorption of acetochlor, using the batch equilibration method, was studied on eight surface soils, one subsurface soil and five sediments collected from the Laborec River and three water reservoirs. Soils and sediments were characterized by commonly used methods for their total organic carbon content, distribution of humus components, pH, grain-size distribution, and smectite content, and for calcium carbonate content. The effect of soil/sediment characteristics on acetochlor sorption-desorption was examined by simple correlation analysis. RESULTS: Sorption of acetochlor was expressed as the distribution coefficient (K (d)). K (d) values slightly decreased as the initial acetochlor concentration increased. These values indicated that acetochlor was moderately sorbed by soils and sediments. Highly significant correlations between the K (d) values and the organic carbon content were observed at both initial concentrations. However, sorption of acetochlor was most closely correlated to the humic acid carbon, and less to the fulvic acid carbon. The total organic carbon content was found to also significantly influence acetochlor desorption. DISCUSSION: Since the strong linear relationship between the K (d) values of acetochlor and the organic carbon content was already released, the corresponding K (oc) values were calculated. Considerable variation in the K (oc) values suggested that other soil/sediment parameters besides the total soil organic carbon content could be involved in acetochlor sorption. This was revealed by a significant correlation between the K (oc) values and the ratio of humic acid carbon to fulvic acid carbon (C(HA)/C(FA)). CONCLUSIONS: When comparing acetochlor sorption in a range of soils and sediments, different K (d) values which are strongly correlated to the total organic carbon content were found. Concerning the humus fractions, the humic acid carbon content was strongly correlated to the K (d) values, and it is therefore a better predictor of the acetochlor sorption than the total organic carbon content. Variation in the K (oc) values was attributed to the differences in distribution of humus components between soils and sediments. Desorption of acetochlor was significantly influenced by total organic carbon content, with a greater organic carbon content reducing desorption. RECOMMENDATIONS AND PERSPECTIVES: This study examined the sorption-desorption processes of acetochlor in soils and sediments. The obtained sorption data are important for qualitative assessment of acetochlor mobility in natural solids, but further studies must be carried out to understand its environmental fate and transport more thoroughly. Although, the total organic carbon content, the humus fractions of the organic matter and the C(HA)/C(FA) ratio were sufficient predictors of the acetochlor sorption-desorption. Further investigations of the structural and chemical characteristics of humic substances derived from different origins are necessary to more preciously explain differences in acetochlor sorption in the soils and sediments observed in this study.

Sorption of acetochlor, atrazine, 2,4-D, chlorotoluron, MCPA, and trifluralin in six soils from Slovakia.

Sorption of the herbicides (acetochlor, atrazine, 2,4-D: , chlorotoluron, MCPA and trifluralin) in their commercially available formulations was characterized on six agricultural soils from Slovakia. Weak acid herbicides (2,4-D: and MCPA) were the least sorbed, whereas weak base such as atrazine and nonionic herbicides were the most sorbed in the order: atrazine < acetochlor approximately chlorotoluron < trifluralin, which was closely related to the hydrophobicity of herbicides expressed as logKOW. The KF values positively correlated with soil organic carbon content for all herbicides. Moreover, all herbicides were the most sorbed by Vertisol with relatively high smectite clay content in proportion to organic carbon content. The KOC values for each herbicide showed a smaller variation among soils (excluding Vertisol) than the KF and were used to compare soil mobility potential of herbicides.

Automated water analyser computer supported system (AWACSS) Part I: Project objectives, basic technology, immunoassay development, software design and networking.

A novel analytical system AWACSS (automated water analyser computer-supported system) based on immunochemical technology has been developed that can measure several organic pollutants at low nanogram per litre level in a single few-minutes analysis without any prior sample pre-concentration nor pre-treatment steps. Having in mind actual needs of water-sector managers related to the implementation of the Drinking Water Directive (DWD) (98/83/EC, 1998) and Water Framework Directive WFD (2000/60/EC, 2000), drinking, ground, surface, and waste waters were major media used for the evaluation of the system performance. The instrument was equipped with remote control and surveillance facilities. The system's software allows for the internet-based networking between the measurement and control stations, global management, trend analysis, and early-warning applications. The experience of water laboratories has been utilised at the design of the instrument's hardware and software in order to make the system rugged and user-friendly. Several market surveys were conducted during the project to assess the applicability of the final system. A web-based AWACSS database was created for automated evaluation and storage of the obtained data in a format compatible with major databases of environmental organic pollutants in Europe. This first part article gives the reader an overview of the aims and scope of the AWACSS project as well as details about basic technology, immunoassays, software, and networking developed and utilised within the research project. The second part article reports on the system performance, first real sample measurements, and an international collaborative trial (inter-laboratory tests) to compare the biosensor with conventional anayltical methods.

Automated Water Analyser Computer Supported System (AWACSS) Part II: Intelligent, remote-controlled, cost-effective, on-line, water-monitoring measurement system.

A novel analytical system AWACSS (Automated Water Analyser Computer Supported System) based on immunochemical technology has been evaluated that can measure several organic pollutants at low nanogram per litre level in a single few-minutes analysis without any prior sample pre-concentration or pre-treatment steps. Having in mind actual needs of water-sector managers related to the implementation of the Drinking Water Directive (DWD) [98/83/EC, 1998. Council Directive (98/83/EC) of 3 November 1998 relating to the quality of water intended for human consumption. Off. J. Eur. Commun. L330, 32-54] and Water Framework Directive (WFD) [2000/60/EC, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Off. J. Eur. Commun. L327, 1-72], drinking, ground, surface, and waste waters were major media used for the evaluation of the system performance. The first part article gave the reader an overview of the aims and scope of the AWACSS project as well as details about basic technology, immunoassays, software, and networking developed and utilised within the research project. The second part reports on the system performance, first real sample measurements, and an international collaborative trial (inter-laboratory tests) to compare the biosensor with conventional anayltical methods. The systems' capability for analysing a wide range of environmental organic micro-pollutants, such as modern pesticides, endocrine disrupting compounds and pharmaceuticals in surface, ground, drinking and waste water is shown. In addition, a protocol using reconstitution of extracts of solid samples, developed and applied for analysis of river sediments and food samples, is presented. Finally, the overall performance of the AWACSS system in comparison to the conventional analytical techniques, which included liquid and gas chromatographic systems with diode-array UV and mass spectrometric detectors, was successfully tested in an inter-laboratory collaborative trial among six project partners.