Comparative studies of the leachate of an industrial landfill by gas chromatography-mass spectrometry, liquid chromatography-nuclear magnetic resonance and liquid chromatography-mass spectrometry

Bisphenol-F and Bisphenol-S (BPF and BPS) Impair the Stemness of Neural Stem Cells and Neuronal Fate Decision in the Hippocampus Leading to Cognitive Dysfunctions

Neurogenesis occurs throughout life in the hippocampus of the brain, and many environmental toxicants inhibit neural stem cell (NSC) function and neuronal generation. Bisphenol-A (BPA), an endocrine disrupter used for surface coating of plastic products causes injury in the developing and adult brain; thus, many countries have banned its usage in plastic consumer products. BPA analogs/alternatives such as bisphenol-F (BPF) and bisphenol-S (BPS) may also cause neurotoxicity; however, their effects on neurogenesis are still not known. We studied the effects of BPF and BPS exposure from gestational day 6 to postnatal day 21 on neurogenesis. We found that exposure to non-cytotoxic concentrations of BPF and BPS significantly decreased the number/size of neurospheres, BrdU+ (proliferating NSC marker) and MAP-2+ (neuronal marker) cells and GFAP+ astrocytes in the hippocampus NSC culture, suggesting reduced NSC stemness and self-renewal and neuronal differentiation and increased gliogenesis. These analogs also reduced the number of BrdU/Sox-2+, BrdU/Dcx+, and BrdU/NeuN+ co-labeled cells in the hippocampus of the rat brain, suggesting decreased NSC proliferation and impaired maturation of newborn neurons. BPF and BPS treatment increases BrdU/cleaved caspase-3+ cells and Bax-2 and cleaved caspase protein levels, leading to increased apoptosis in hippocampal NSCs. Transmission electron microscopy studies suggest that BPF and BPS also caused degeneration of neuronal myelin sheath, altered mitochondrial morphology, and reduced number of synapses in the hippocampus leading to altered cognitive functions. These results suggest that BPF and BPS exposure decreased the NSC pool, inhibited neurogenesis, induced apoptosis of NSCs, caused myelin degeneration/synapse degeneration, and impaired learning and memory in rats.

Using size-exclusion for improved extraction of trace organic compounds from landfill leachate

Pharmaceuticals, plasticisers and other trace organic contaminants have been reported in landfill leachates, with most methods using hydrophilic-lipophilic balance cartridges for solid phase extraction. However, leachate has a high organic load and can quickly coat the cartridge media and prevent target compounds from being extracted. There are several solid phase extraction cartridges that offer size exclusion in addition to adsorption, where only small molecules are allowed to diffuse into the resin pores where adsorption in happening. Three cartridges with size exclusion properties were evaluated in comparison with hydrophilic-lipophilic balance cartridges for extraction of several trace organic contaminants spiked into landfill leachate. All three cartridges with size exclusion properties showed some improvement in extraction compared with hydrophilic-lipophilic balance, although the differences were not statistically significant at 95% confidence interval. Nevertheless, media with size-exclusion properties offers a viable alternative to hydrophilic-lipophilic balance for extracting small molecules of trace organics from complex environmental matrices.

Investigating landfill leachate toxicity in vitro: A review of cell models and endpoints

Landfill leachate is a complex mixture characterized by high toxicity and able to contaminate soils and waters surrounding the dumpsite, especially in developing countries where engineered landfills are still rare. Leachate pollution can severely damage natural ecosystems and harm human health. Traditionally, the hazard assessment of leachate is based on physicochemical characterization but the toxicity is not considered. In the last few decades, different bioassays have been used to assess the toxicity of this complex matrix, including human-related in vitro models. This article reviews the cell bioassays successfully used for the risk assessment of leachate and to evaluate the efficiency of toxicity removal of several processes for detoxification of this wastewater. Articles from 2003 to 2018 are covered, focusing mainly on studies that used human cell lines, highlighting the usefulness and adequacy of in vitro models for assessing the hazard involved with exposure to leachate, particularly as an integrative supporting tool for chemical-based risk assessment. Leachate is generally toxic, mutagenic, genotoxic and estrogenic in vitro, and these effects can be measured in the cells exposed to already low concentrations, confirming the serious hazard of this wastewater for human health.

Leachate composition and toxicity assessment: an integrated approach correlating physicochemical parameters and toxicity of leachates from MSW landfill in Delhi

Landfills are considered the most widely practiced method for disposal of municipal solid waste (MSW) and 95% of the total MSW collected worldwide is disposed of in landfills. Leachate produced from MSW landfills may contain a number of pollutants and pose a potential environmental risk for surface as well as ground water. In the present study, chemical analysis and toxicity assessment of landfill leachate have been carried out. Leachate samples were collected from Ghazipur landfill site, New Delhi. Leachates were characterized by measuring the concentration of heavy metals (Pb, Cu, Cr and Ni), 5-day biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), pH, electrical conductivity and SO₄²-. For toxicity testing of leachate, Triticum aestivum (wheat) was selected and testing was done in a time- and dose-dependent manner using the crude leachate. Median lethal concentration after 24 and 48 h of exposure was observed. The main objective of this study was to evaluate toxicity of MSW landfill leachate and establish a possible correlation between the measured physicochemical parameters and resultant toxicity. Statistical analysis showed that toxicity was dependent on the concentration of heavy metals (Pb, Cu), conductivity, and organic matter (COD and BOD5).

Powdered ZELIAC augmented sequencing batch reactors (SBR) process for co-treatment of landfill leachate and domestic wastewater

Sequencing batch reactor (SBR) is one of the various methods of biological treatments used for treating wastewater and landfill leachate. This study investigated the treatment of landfill leachate and domestic wastewater by adding a new adsorbent (powdered ZELIAC; PZ) to the SBR technique. ZELIAC consists of zeolite, activated carbon, lime stone, rice husk ash, and Portland cement. The response surface methodology and central composite design were used to elucidate the nature of the response surface in the experimental design and describe the optimum conditions of the independent variables, including aeration rate (L/min), contact time (h), and ratio of leachate to wastewater mixture (%; v/v), as well as their responses (dependent variables). Appropriate conditions of operating variables were also optimized to predict the best value of responses. To perform an adequate analysis of the aerobic process, four dependent parameters, namely, chemical oxygen demand (COD), color, ammonia-nitrogen (NH3-N), and phenols, were measured as responses. The results indicated that the PZ-SBR showed higher performance in removing certain pollutants compared with SBR. Given the optimal conditions of aeration rate (1.74 L/min), leachate to wastewater ratio (20%), and contact time (10.31 h) for the PZ-SBR, the removal efficiencies for color, NH3-N, COD, and phenols were 84.11%, 99.01%, 72.84%, and 61.32%, respectively.

Development of a screening method for the determination of xenobiotic organic pollutants in municipal landfill leachate using solvent extraction and comprehensive GCxGC-qMS analysis

In the present study, we propose a method for the evaluation of different classes of xenobiotic organic compounds enclosed in the municipal landfill leachate using comprehensive two-dimensional gas chromatography coupled with quadrupole mass spectrometry (GCxGC-qMS). Here we show that, due to high peak capacity of comprehensive two-dimensional gas chromatography, in a single run it is possible to separate compounds with different physical-chemical properties (such as aliphatic and aromatic compounds, polyaromatic hydrocarbons, phenols, phthalates, aldehydes, ketones, nitrogen containing compounds, organo-phosphoric flame retardants etc.), compounds which have proved to be endocrine disruptors, compounds that are persistent, bioaccumulative and toxic, carcinogenic, mutagenic, teratogenic, reprotoxic or harmful for the environment. Even though a solvent extraction method has been optimised, the extraction step still remains the main problem for a comprehensive characterization of all classes of organic toxicants enclosed in the municipal landfill leachate.

Toxicological review and oral risk assessment of terephthalic acid (TPA) and its esters: A category approach

Polyethylene terephthalate, a copolymer of terephthalic acid (TPA) or dimethyl terephthalate (DMT) with ethylene glycol, has food, beverage, and drinking water contact applications. Di-2-ethylhexyl terephthalate (DEHT) is a plasticizer in food and drinking water contact materials. Oral reference doses (RfDs) and total allowable concentrations (TACs) in drinking water were derived for TPA, DMT, and DEHT. Category RfD and TAC levels were also established for nine C(1)-C(8) terephthalate esters. The mode of action of TPA, and of DMT, which is metabolized to TPA, involves urinary acidosis, altered electrolyte elimination and hypercalciuria, urinary supersaturation with calcium terephthalate or calcium hydrogen terephthalate, and crystallization into bladder calculi. Weanling rats were more sensitive to calculus formation than dams. Calculi-induced irritation led to bladder hyperplasia and tumors in rats fed 1000 mg/kg-day TPA. The lack of effects at 142 mg/kg-day supports a threshold for urine saturation with calcium terephthalate, a key event for calculus formation. Chronic dietary DMT exposure in rodents caused kidney inflammation, but not calculi. Chronic dietary DEHT exposure caused general toxicity unrelated to calculi, although urine pH was reduced suggesting the TPA metabolite was biologically-active, but of insufficient concentration to induce calculi. Respective oral reference doses of 0.5, 0.5, and 0.2 mg/kg-day and total allowable drinking water concentrations of 3, 3, and 1 mg/L were derived for TPA, DMT, and DEHT. An oral RfD of 0.2 mg/kg-day for the terephthalate category chemicals corresponded to a drinking water TAC of 1 mg/L.

Migration behavior of landfill leachate contaminants through alternative composite liners

Four identical pilot-scale landfill reactors with different alternative composite liners were simultaneously operated for a period of about 540 days to investigate and to simulate the migration behaviors of phenolic compounds (phenol, 2-CP, 2-MP, 3-MP, 4-MP, 2-NP, 4-NP, 2,4-DNP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,4,6-TCP, 2,3,4,6-TeCP, PCP) and heavy metals (Pb, Cu, Zn, Cr, Cd, Ni) from landfill leachate to the groundwater. Alternative landfill liners of four reactors consist of R1: Compacted clay liner (10 cm+10 cm, k=10(-8)m/sn), R2: Geomembrane (2 mm HDPE)+compacted clay liner (10 cm+10 cm, k=10⁻⁸ m/sn), R3: Geomembrane (2 mm HDPE)+compacted clay liner (10 cm, k=10⁻⁸ m/sn)+bentonite liner (2 cm)+compacted clay liner (10 cm, k=10⁻⁸ m/sn), and R4: Geomembrane (2 mm HDPE)+compacted clay liner (10 cm, k=10⁻⁸ m/sn)+zeolite liner (2 cm)+compacted clay liner (10 cm, k=10⁻⁸ m/sn). Wastes representing Istanbul municipal solid wastes were disposed in the reactors. To represent bioreactor landfills, reactors were operated by leachate recirculation. To monitor and control anaerobic degradation in the reactors, variations of conventional parameters (pH, alkalinity, chloride, conductivity, COD, TOC, TKN, ammonia and alcaly metals) were also investigated in landfill leachate samples. The results of this study showed that about 35-50% of migration of organic contaminants (phenolic compounds) and 55-100% of migration of inorganic contaminants (heavy metals) to the model groundwater could be effectively reduced with the use of bentonite and zeolite materials in landfill liner systems. Although leachate contaminants can reach to the groundwater in trace concentrations, findings of this study concluded that the release of these compounds from landfill leachate to the groundwater may potentially be of an important environmental concern based on the experimental findings.

A combined approach to investigate the toxicity of an industrial landfill's leachate: chemical analyses, risk assessment and in vitro assays

Solid wastes constitute an important and emerging problem. Landfills are still one of the most common ways to manage waste disposal. The risk assessment of pollutants from landfills is becoming a major environmental issue in Europe, due to the large number of sites and to the importance of groundwater protection. Furthermore, there is lack of knowledge for the environmental, ecotoxicological and toxicological characteristics of most contaminants contained into landfill leacheates. Understanding leachate composition and creating an integrated strategy for risk assessment are currently needed to correctly face the landfill issues and to make projections on the long-term impacts of a landfill, with particular attention to the estimation of possible adverse effects on human health and ecosystem. In the present study, we propose an integrated strategy to evaluate the toxicity of the leachate using chemical analyses, risk assessment guidelines and in vitro assays using the hepatoma HepG2 cells as a model. The approach was applied on a real case study: an industrial waste landfill in northern Italy for which data on the presence of leachate contaminants are available from the last 11 years. Results from our ecological risk models suggest important toxic effects on freshwater fish and small rodents, mainly due to ammonia and inorganic constituents. Our results from in vitro data show an inhibition of cell proliferation by leachate at low doses and cytotoxic effect at high doses after 48 h of exposure.

Assessing the environmental risks associated with contaminated sites: Definition of an Ecotoxicological Classification index for landfill areas (ECRIS)

Assessing ecological risk in quantitative terms is a site-specific complex procedure requiring evaluation of all possible pathways taken by the chemicals from the contamination source to the targets to be protected. Unfortunately, too many cases lack of physico-chemical and ecotoxicological data makes impossible to quantify the ecological risk. We present the Ecotoxicological Classification Risk Index for Soil (ECRIS), a new classification system specific for soil risk assessment, which gives a comparative indication of the risk linked to environmental contamination by any chemical. The tool we propose is based on the integration of a data set characterizing the ecotoxicological and exposure profile of chemicals. ECRIS is a simple approach specifically set up for the landfill scenario. This index draws on the huge amount of data from our many years of leachate analysis. ECRIS is useful for a first screening of probably contaminated soil. A case study based on some Italian landfills is proposed.

Biodegradation of bisphenol A, bisphenol F and bisphenol S in seawater

A group of compounds structurally similar to bis(4-hydroxyphenyl)propane (bisphenol A, BPA) are called bisphenols (BPs), and some of them can partially replace BPA in industrial applications. The production and consumption of BPs other than BPA, especially those of bis(4-hydroxyphenyl)methane (bisphenol F, BPF) and bis(4-hydroxyphenyl)sulfone (bisphenol S, BPS), have increased recently, leading to their detection as contaminants in the aquatic environment. The three compounds tested 100% positive for estrus response in 1936 and concerns about their health risks have been increasing. Abundant data on degradation of bisphenols (BPs) has been published, but results for biodegradation of BPs in seawater are lacking. However, several research groups have focused on this topic recently. In this study, the biodegradation behaviors of three BPs, namely BPA, BPF and BPS, in seawater were investigated using TOC Handai (TOC, potential test) and river (sea) die-away (SDA, simulation test) methods, which are both a kind of river-die-away test. The main difference between the tests is that indigenous microcosms remain in the sampled raw seawater for the SDA experiments, but they are removed through filtration and dispersed into artificial seawater for the TOC experiments. The BPs, except for BPS, were degraded using both methods. The SDA method produced better biodegradation results than the TOC method in terms of degradation time (both lag and degradation periods). Biodegradation efficiencies were measured at 75–100% using the SDA method and 13–63% using the TOC method. BPF showed better degradation efficiency than BPA, BPF was > 92% and BPA 83% depleted according to the SDA tests. BPS degradation was not observed. As a conclusion, the biodegradability of the three BPs in seawater could be ranked as BPF > BPA ≫ BPS. BPF is more biodegradable than BPA in seawater and BPS is more likely to accumulate in the aquatic environment. BPS poses a lower risk to human health and to the environment than BPA or BPF but it is not amenable to biodegradation and might be persistent and become an ecological burden. Thus other degradation methods need to be found for the removal of BPS in the environment.

Implementation of real-time two-dimensional nuclear magnetic resonance spectroscopy for on-flow high-performance liquid chromatography

Directly coupled HPLC-NMR has become a powerful tool for separation and structural elucidation of unknown compounds. However, there are only a few reports on application of on-flow two-dimensional (2D) NMR in HPLC-NMR. Here we present an alternative method for recording real-time 2D-NMR spectrum (total correlation spectroscopy, TOCSY) on a commercial HPLC-NMR system. The method is based on well-established Hadamard matrix for 2D-NMR frequency encoding. In addition, a modified/improved solvent suppression approach is incorporated. This makes it possible to carry out the experiment with both polar and gradient eluents, the widely used chromatographic conditions. The method is example using a synthesized mixture of three amino acids (His, Phe and Try) and a human urine sample. The method demonstrated here may be utilized for high-throughput structural or unknown component identification and fast dynamic study in a variety of applications.

Characterization of an urban landfill soil by using physicochemical analysis and solid phase microextraction (SPME)-GC/MS

We have aimed at characterizing top soil samples taken in-situ from five different locations of the unregulated dumping site in Eskişehir/Turkey for a period of six months. The study is the first attempt in the city and in Turkey, regarding particularly the SPME (Solid Phase Microextraction Technique) analysis method utilized. A comprehensive research has been conducted to produce critical soil data to be used for indicating current risks as well as the urgency of rehabilitating the site and establishing a sanitary landfill in the site. Conventional physicochemical analytical methods and SPME technique were used to analyze the samples. Physicochemical analyses were performed for determining the pH, total dried matter, volatile matter, total nitrogen, phosphorus, macro elements and heavy metals. Meteorological data were also recorded for the same period. SPSS.10.0 statistical program was used to determine the correlation between meteorological data and physicochemical analysis results. Mean values were used in the correlation analyses. These data indicated that the air temperature and precipitation have significant effects on soil characteristics. SPME, coupled with GC/MS, was used to identify eighty six volatile and semi-volatile organic compounds contained in soil samples. The samples were extracted by headspace SPME with heating (DeltaHS-SPME). SPME analyses were conducted using a commercially available polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber having a film thickness of 65 microm (Supelco) as a capture medium. The experimentally optimized headspace sampling conditions were arranged (15 min. at 50 degrees C) before a 30 min. sampling period.

Characterization of the leachate in an urban landfill by physicochemical analysis and solid phase microextraction-GC/MS

The aim of this study is to evaluate extensively the characterization and identification of major pollutant parameters by paying attention to the organic chemical pollution for unregulated dumping site leachate in Eskişehir/Turkey. The study that is first and only one research has been very important data related with before new sanitary landfill site in Eskişehir city. For this purpose, in this study leachate samples were collected in-situ at monthly interval for a period of 8 months. Firstly, thirty three physicochemical parameters were monitored. Secondly, SPME technique was used for identification of organic pollutants. Meteorological data were also recorded for the same sampling period to correlate meteorological data and physicochemical parameters. Mean values are used in the correlation analysis. Correlation is shown only for the relationship between air temperature and NO(3) (-). No correlation has been found between rain and leachate quality parameters since the amount of rain was very low during the sampling period. However, analysis results were generally decreased in winter season when each parameter and each sampling point are examined separately. According to correlation between every parameter, especially solid content and dissolved oxygen concentration of leachate is affecting to other parameters. Also, sodium and potassium are changing proportionally with same parameters (suspended solids, fixed solids, dissolved oxygen) and high correlation between chloride and heavy metal concentration is showing. The results were statistically evaluated by use of SPSS 10.0 program. Second part of the study, the leachate was extracted by Solid Phase Microextraction (SPME) technique and then analyzed. Of the methodologies tested in this study, the best one selected was based on 100 micro m polydimethylsiloxane coated fiber (PDMS), headspace with heating (Delta HS) sampling mode and an extraction time of 15 min. at a temperature of 50 degrees C. Thirty three organic compounds in leachate were identified by GC/MS.

Development of HPLC/ESI-MS and HPLC/1H NMR Methods for the Identification of Photocatalytic Degradation Products of Iodosulfuron

In the present study, HPLC/ESI-MS and stopped-flow HPLC/1H NMR methods were developed and applied to separate and characterize the byproducts arising from TiO2-catalyzed photodegradation of the herbicide iodosulfuron methyl ester (IOME) in aqueous solution under UV irradiation. Prior to identification, irradiated solutions of IOME (200 and 1000 mg.L(-1)) were concentrated by solid-phase extraction using two cartridges: Isolute C18 and Isolute ENV+. Analytical separation was achieved on a C18 reversed-phase column with ACN/H2O (HPLC/MS) or ACN/D2O (HPLC/NMR) as mobile phase and a linear gradient with a chromatographic run time of 35 min. The combination of UV and MS data allowed the structural elucidation of more than 20 degradation products, whereas 1H NMR data permitted an unequivocal confirmation of the identities of major products and the differentiation of several positional isomers, in particular, the hydroxylation isomers. The obtained results permitted us to propose a possible degradation scheme and to put in evidence the presence of privileged sites for the attack of OH radicals. This work shows, for the first time, the application of combined HPLC with UV, MS, and NMR detection for complete structural elucidation of photocatalytic degradation products, and it will be of particular value in studies on the elimination of pollutants in aqueous solutions by photocatalysis.

Organic tracers identification as a convenient strategy in industrial landfills monitoring

Today, a significant environmental problem is due to the presence of industrial landfills, some of them old, which can release toxic compounds into the environment (Chemosphere 42 (2001) 415; Chemosphere 31 (1995) 3455). The identification of directly linked to the leachate tracers of contamination in the wells around the landfills, as early markers of a potential risk for the environment and/or man, is a good strategy for an early evaluation of contamination. Our protocol developed for wells water characterization is based on solid phase extraction combined with GC-MS and HPLC-MS/MS. In this way a list of organic contaminants of a specific industrial landfill is obtained, giving a solid basis also for the risk assessment. Here we present some specific examples and the use of these pollutants for environmental monitoring.

Development and substantiation of a liquid chromatographic method for monitoring organic reactions involved in synthesis of 4-methoxyphenylacetic acid

A simple and rapid reversed-phase high-performance liquid chromatographic method for monitoring the reactions involved in two different processes for the production of 4-methoxyphenylacetic acid (PMPA) was developed. Impurity profiles of PMPA were used for fingerprinting of the two different synthetic processes by HPLC. Impurities were separated and determined on a Hypersil C18 column with acetonitrile-0.1 M potassium dihydrogen orthophosphate-triethylamine (40:59.95:0.05, v/v) (pH 3.0) as the mobile phase and detection at 280 nm at ambient temperature. The method was substantiated with respect to accuracy, precision, linearity, robustness, limit of detection and quantification. The method was found to be suitable not only for monitoring the reactions but also for quality assurance of PMPA as it could detect impurities at the level of 4 x 10(-9) g.

Determination of tacrine metabolites in microsomal incubate by high performance liquid chromatography-nuclear magnetic resonance/mass spectrometry with a column trapping system

A column trapping system has been incorporated into high performance liquid chromatography-nuclear magnetic resonance-mass spectrometry (HPLC-NMR-MS) to reduce data acquisition time of NMR experiments. The system uses a trapping column to capture analytes after the HPLC column and back flush trapped analyte to the flow cell of the NMR probe for detection. A dilution solvent is mixed with eluent from HPLC column to reduce the influence of the organic content in the mobile phase before column trapping. The trapping column is also coupled with a mass spectrometer (MS) to get complementary MS data on the same peak. Studies on 1-hydroxylated 9-amino-1,2,3,4-tetrahydro-acridine (1-OH tacrine), indomethacin and testosterone with the column trapping system showed good recovery of analytes and over 3-fold mean increase in UV-VIS signal intensity. The time saving on NMR experiments with the column trapping system was demonstrated by the analysis of dog microsomal incubate with tacrine.

Acute toxicity, mutagenicity, and estrogenicity of bisphenol-A and other bisphenols

Although abundant data are available on the toxicity of bisphenol-A (2,2-bis (4-hydroxydiphenyl)propane; BPA), little is known about the toxicities of the structurally similar compounds, namely bisphenols (BPs). A variety of BPs were examined for their acute toxicity against Daphnia magna, mutagenicity, and estrogenic activity using the Daphtoxkit (Creasel Ltd.), the umu test system, and the yeast two-hybrid system, respectively, in comparison with BPA. BPA was moderately toxic to D. magna (48-h EC50 was 10 mg/l) according to the current U.S. EPA acute toxicity evaluation standard, and it was weakly estrogenic with 5 orders of magnitude lower activity than that of the natural estrogen 17 beta-estradiol in the yeast screen, while no mutagenicity was observed. All seven BPs tested here showed moderate to slight acute toxicity, no mutagenicity, and weak estrogenic activity as well as BPA. Some of the BPs showed considerably higher estrogenic activity than BPA, and others exhibited much lower activity. Among the tested BPs, two compounds, i.e., bisphenol-S (bis(4-hydroxydiphenyl)sulfone) and bis(4-hydroxyphenyl)sulfide, have never been reported for their estrogenic activity previously.

Preconcentration of contaminants in water analysis

Among the environmental areas, in this review attention will be focused on water matrices and both on organic (e.g., pesticides, herbicides, phenols, polycyclic aromatic hydrocarbons), inorganic species and anion pollutants, since these kinds of substances include a wide number of compounds with different physical and chemical properties and different effects on human health. Analytical methods for control of quality of waters are required to be highly specific and possibly highly sensitive for the determination of even low amounts of pollutants. The main problems encountered during the analysis are the separation of matrix components from the pollutants of interest and the achievement of low detection limits. Therefore an overview on different materials and techniques available for sample concentration and/or matrix removal will be provided and discussed according to the chemical characteristics of the pollutant that has to be enriched.

Solid-phase trapping of solutes for further chromatographic or electrophoretic analysis

Because of its simplicity, speed and effectiveness, solid-phase extraction (SPE) has become the preferred technique for concentration of selected analytes prior to chromatographic or electrophoretic analysis. In this review the historical development of SPE is briefly traced. Then the principles of SPE are reviewed in some detail. Numerous references are given on the format, sorbents, elution conditions, online techniques and automation with special emphasis on relatively recent developments. The principles and recent advances in solid-phase microextraction (SPME) are also reviewed. The final section on selected recent applications includes an extensive list of references to work published within the last three years. Future trends and developments are discussed briefly.