Determination of priority phenolic compounds in water and industrial effluents by polymeric liquid-solid extraction cartridges using automated sample preparation with extraction columns and liquid chromatography use of liquid-solid extraction cartridges for stabilization of phenols

Mechanism and thermal rate constants for complete series reactions of bromochlorophenols with H

Formation of bromochlorophenoxy radicals (BCPRs) from the reaction of bromochlorophenols (BCPs) with H can play the most central role in the formation of mixed polybrominated and chlorinated dibenzo-p-dioxins and dibenzofurans (PBCDD/Fs).

Toxicological profile of chlorophenols and their derivatives in the environment: the public health perspective

Chlorophenol compounds and their derivatives are ubiquitous contaminants in the environment. These compounds are used as intermediates in manufacturing agricultural chemicals, pharmaceuticals, biocides, and dyes. Chlorophenols gets into the environment from a variety of sources such as industrial waste, pesticides, and insecticides, or by degradation of complex chlorinated hydrocarbons. Thermal and chemical degradation of chlorophenols leads to the formation of harmful substances which constitute public health problems. These compounds may cause histopathological alterations, genotoxicity, mutagenicity, and carcinogenicity amongst other abnormalities in humans and animals. Furthermore, the recalcitrant nature of chlorophenolic compounds to degradation constitutes an environmental nuisance, and a good understanding of the fate and transport of these compounds and their derivatives is needed for a clearer view of the associated risks and mechanisms of pathogenicity to humans and animals. This review looks at chlorophenols and their derivatives, explores current research on their effects on public health, and proffers measures for mitigation.

Use of Cl and C isotopic fractionation to identify degradation and sources of polychlorinated phenols: mechanistic study and field application

The widespread use of chlorinated phenols (CPs) as a wood preservative has led to numerous contaminated sawmill sites. However, it remains challenging to assess the extent of in situ degradation of CPs. We evaluated the use of compound-specific chlorine and carbon isotope analysis (Cl- and C-CSIA) to assess CP biotransformation. In a laboratory system, we measured isotopic fractionation during oxidative 2,4,6-trichlorophenol dechlorination by representative soil enzymes (C. fumago chloroperoxidase, horseradish peroxidase, and laccase from T. versicolor). Using a mathematical model, the validity of the Rayleigh approach to evaluate apparent kinetic isotope effects (AKIE) was confirmed. A small but significant Cl-AKIE of 1.0022 ± 0.0006 was observed for all three enzymes, consistent with a reaction pathway via a cationic radical species. For carbon, a slight inverse isotope effect was observed (C-AKIE = 0.9945 ± 0.0019). This fractionation behavior is clearly distinguishable from reported reductive dechlorination mechanisms. Based on these results we then assessed degradation and apportioned different types of technical CP mixtures used at two former sawmill sites. To our knowledge, this is the first study that makes use of two-element CSIA to study sources and transformation of CPs in the environment.

Simultaneous determination of five nitroaniline and dinitroaniline isomers in wastewaters by solid-phase extraction and high-performance liquid chromatography with ultraviolet detection

A high-performance liquid chromatography (HPLC)-ultraviolet detection method, combined with solid-phase extraction (SPE), was developed for the determination of five nitroaniline and dinitroaniline isomers including 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline and 2,6-dinitroaniline in wastewater samples. Extraction of the five isomers was carried out with a hydrophile-lipophile balance cartridge, the Oasis HLB. The cartridge was washed by a mixed aqueous solution containing 10% (v/v) acetonitrile and 10% (v/v) ethyl acetate before the five isomers were eluted by a mixture of methanol and acetic acid. Separation of the five isomers was achieved by using an Agilent TC-C(18) column at 30°C, and using a mixture of acetonitrile/water 30/70 (v/v) as mobile phase under an isocratic condition at a flow rate of 1.0 mL/min. The analytes were detected by a UV detector at a wavelength of 225 nm. Recoveries of the five isomers in the spiked sewage sample were between 84.6% and 94.0% with a relative standard deviation of less than 4.7%. The limits of quantification (LOQ) determined in a spiked sewage sample of 500 mL were 2.0 x 10(-9)M for 2-nitroaniline, 3-nitroaniline and 2,6-dinitroaniline, and 4.5 x 10(-9)M for 4-nitroaniline and 2,4-dinitroaniline. The proposed method was applied to determine the five isomers in real samples of acidic wastewater and printing and dyeing wastewater.

Oxidized multiwalled carbon nanotubes as a novel solid-phase microextraction fiber for determination of phenols in aqueous samples

A simple and environmentally friendly method for determination of seven phenols using solid-phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) has been developed. Several materials were used as stationary phase of SPME fibers and an oxidized multiwalled carbon nanotubes material was found to be effective in carrying out simultaneous extraction of phenols in aqueous samples. Compared with the widely used commercially available SPME fibers, this proposed fiber had much lower cost, longer lifetime (over 150 times), shorter analysis time (30 min of extraction and 3 min of desorption time) and comparable or superior extraction efficiency for the investigated analytes. The extraction and desorption conditions were evaluated and the calibration curves of seven phenols were linear (R(2)> or =0.9908) in the range from 10.2 to 1585 ng mL(-1). The limits of detection at a signal-to-noise (S/N) ratio of 3 were 0.25-3.67 ng mL(-1), and the limits of quantification calculated at S/N=10 were 0.83-12.25 ng mL(-1) for these compounds. The possibility of applying the proposed method to environmental water samples analysis was validated.

Comparison of the performance of different reversed-phase columns for liquid chromatography separation of 11 pollutant phenols

A systematic optimization of the HPLC separation of a mixture containing 11 pollutant phenols (PPs) using a Hypersil ODS (250 mm x 4.6 mm, 5 microm) column and UV-DAD detection has been carried out. The binary mobile phases used were obtained by mixing 50 mM phosphate (pH = 3.0) and methanol, ACN, or THF as organic modifiers. After selecting ACN as an organic modifier, the effects of pH and temperature on PPs separation were studied. A mobile phase of 50 mM acetate (pH = 5.0)-ACN (60:40 v/v) at 50 degrees C allowed the separation of 11 phenols but not to baseline in 17 min. To improve the performance of this separation, the following RP columns were tested: Luna C18 (2), Purospher C18, Synergi C12, Synergi Fusion C18, Gemini C18, Luna Cyano, Lichrospher C8, and Envirosep-PP (polymeric). In all the cases, the performance (analysis time, retention, selectivity, resolution, asymmetry factors, and efficiency) was evaluated. A further reoptimization of the mobile phase was carried out for all the columns by studying the ACN content and pH, with the aim of improving the above-mentioned separations and selecting the most suitable one for PPs analysis.

Use of coacervates for the on-site extraction/preservation of polycyclic aromatic hydrocarbons and benzalkonium surfactants

The suitability of coacervates for the preservation of organic pollutants after their extraction from water samples was investigated for the first time. Acid-induced sodium dodecanesulfonic acid (SDSA) micelle-based coacervates were selected for this purpose. Their capacity to preserve benzalkonium homologue (C(12), C(14) and C(16)) surfactants (BASs) and different polycyclic aromatic hydrocarbons (PAHs) [benzo(a)pyrene (BaP), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(ghi)perylene (BghiP), benzo(a)anthracene (BaA) and indene(1,2,3-c-d)pyrene (IP)] was investigated. BASs and PAHs were efficiently extracted by the coacervate by formation of mixed aggregates and hydrophobic interactions, respectively. Their stability into the coacervate was investigated under three temperature conditions (room temperature, 4 degrees C and -20 degrees C) and two hydrochloric acid concentrations (3.75 M and 4.2 M), which was used to induce coacervation. No losses were observed during at least 3 months at the different experimental conditions tested. The increase of the temperature up to 35 degrees C for a month did not affect the stability of the target compounds. No influence of the water matrix (distilled, river or wastewater) on the stabilization of BASs and PAHs was observed. The high-stabilizing capacity of the coacervate for the target compounds and its low volume make easy the transport and storage of analytes.

Extraction of hydroxyaromatic compounds in river water by liquid–liquid–liquid microextraction with automated movement of the acceptor and the donor phase

Liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase technique is described for the extraction of six hydroxyaromatic compounds in river water using a disposable and ready to use hollow fiber. Separation and quantitative analyses were performed using LC with UV detection at 254 nm. Analytes were extracted from the acidified sample solution (donor phase) into the organic solvent impregnated in the pores of the hollow fiber and then back extracted into the alkaline solution (acceptor phase) inside the lumen of the hollow fiber. The fiber was held by a conventional 10 microL LC syringe. The acceptor phase was sandwitched between the plunger and a small volume of the organic solvent (microcap). The acceptor solution was repeatedly moved in and out of the hollow fiber using a syringe pump. This movement provides a fresh acceptor phase to come in contact with the organic phase and thus enhancing extraction kinetics thereby leading to the improvement in enrichment of the analytes. The microcap separates the acceptor phase and the donor phase in addition to being partially responsible for mass transfer of the analytes from the donor solution to the acceptor solution. Under stirring, a fresh donor phase will enter through the open end of the fiber that will also contribute to the mass transfer. Various parameters affecting the extraction efficiency viz type of organic solvent, extraction time, stirring speed, effect of sodium chloride, and concentration of donor and acceptor phases were studied. RSD (3.9-5.6%), correlation coefficient (0.995-0.997), detection limit (2.0-51.2 ng/mL), enrichment factor (339-630), relative recovery (93.2-97.9%), and absolute recovery (33.9-63.0%) have also been investigated. The developed method was applied for the analysis of river water.

Stability of benzalkonium surfactants on hemimicelle-based solid-phase extraction cartridges

The capability of hemimicelle-based solid-phase extraction cartridges for the preservation of organic compounds after their concentration from water samples was investigated for the first time. The approach is illustrated by studying the stability of benzalkonium homologue (C12, C14 and C16) surfactants (BAS) on monolayers of dodecyl sulphate (SDS) hemimicelles formed on alumina. The stability study included storage of cartridges at room temperature, at 4 and -20 degrees C, during a period of up to 3 months. The influence of water matrix components was also investigated from parallel experiments using spiked distilled, river and wastewater samples. Complete recovery of BAS was obtained for all storage conditions tested. Recoveries were independent on the alkyl chain length of BAS homologues and water matrix. The SPE of BAS on the SDS hemimicelles had a strong stabilizing effect for the target compounds and their analysis can be accomplished after at least 3 months without the necessity of special storage conditions for cartridges. Because of the lack of data, an additional stability study was carried out for BAS in an aqueous matrix using traditional preservation methods such as acidification (pH 2)/refrigeration, addition of formaldehyde (5%)/refrigeration, and freezing (-20 degrees C). Only combination of chemical addition (e.g. nitric acid or formaldehyde)/refrigeration was found effective to preserve BAS in the short term (e.g. for a week), then losses up to 40% were observed for these target compounds after a month.

Membrane-assisted solvent extraction of seven phenols combined with large volume injection-gas chromatography-mass spectrometric detection

Membrane-assisted solvent extraction (MASE) was applied for the determination of seven phenols (phenol, 2-chlorophenol, 2,4-dimethylphenol, 2,4-dichlorophenol, 4-chloro-3-methylphenol, 2,4,6-trichlorophenol and pentachlorophenol) with log Kow (octanol-water-partition-coefficient) between 1.46 (phenol) and 5.12 (pentachlorophenol) in water. The extraction solvents cyclohexane, ethyl acetate and chloroform were tested and ethyl acetate proved to be the best choice. The optimisation of extraction conditions showed the necessity of adding 5 g of sodium chloride to each aqueous sample to give a saturated solution (333 g/L). The pH-value of the sample was adjusted to 2 in order to convert all compounds into their neutral form. An extraction time of 60 min was found to be optimal. Under these conditions the recovery of phenol, the most polar compound, was 11%. The recoveries of the other analytes ranged between 42% (2-chlorophenol) and 98% (2,4-dichlorophenol). Calibration was performed using large volume injection (100 microL injection volume). At optimised conditions the limits of detection were between 0.01 and 0.6 microg/L and the relative standard deviation (n = 3) was on average about 10%. After the method optimisation with reagent water membrane-assisted solvent extraction was applied to two contaminated ground water samples from the region of Bitterfeld in Saxony-Anhalt, Germany. The results demonstrate the good applicability of membrane-assisted solvent extraction for polar analytes like phenols, without the necessity of derivatisation or a difficult and time-consuming sample preparation.

Spectrophotometric detection of pentachlorophenol (PCP) in water using immobilized and water-soluble porphyrins

The spectrophotometric properties of porphyrins are altered upon interaction with chlorophenols and other organochlorine pollutants. Meso-tetra(4-sulfonatophenyl)porphyrin (TPPS), zinc meso-tetra(4-sulfonato phenyl)porphyrin (Zn-TPPS), monosulfonate-tetraphenylporphyrin (TPPS1), meso-tri(4-sulfonatophenyl)mono(4-carboxyphenyl)porphyrin (C1TPP), meso-tetra(4-carboxyphenyl)porphyrin (C4TPP), and copper meso-tetra(4-carboxyphenyl)porphyrin (Cu-C4TPP) in solution exhibit a broad absorbance in the range 400-450 nm Soret region. The interaction of the above mentioned porphyrins in solution with pentachlorophenol (PCP) induces a red shift in the Soret spectrum with absorbance losses at 413, 418, 403, 405, 407, and 404 nm, respectively, and the appearance of new peaks at 421, 427, 431, 416, 417, and 416 nm, respectively. The intensity of the Soret spectral change is proportional to the pentachlorophenol concentration with a detection limit of 1, 0.5, 1.16, 1, 0.5, and 0.5 ppb, respectively. The interaction of (C4TPP) and (Cu-C4TPP) in solution with PCP shows to concentration dependent for concentrations less than 4 ppb the dependence was log-linear. However, for concentrations greater than 4 ppb the relation was linear. Monosulfonate-tetraphenylporphyrin immobilized as a monolayer on a Kimwipe tissue exhibits an absorbance peak in the Soret region at 422 nm. The interaction of the porphyrin with PCP induces a red shift in the Soret spectrum with absorbance loss at 419 nm and the appearance of new peaks at 446 nm. The intensity of the Soret spectral change is proportional to the log of PCP concentration. The detection limit with immobilized TPPS1 for PCP is 0.5 ppb. These results suggest the potential for development of spectrophotometric chemosensor for PCP residues in water with detection limits less than US EPA maximum contaminate level (MCL) of 1 ppb. The immobilized TPPS1 on the Kimwipe will make it possible to develop a wiping sensors to monitor the PCP or other pesticides residues on the vegetables or wood products.

Solid-phase extraction of polar compounds with a hydrophilic copolymeric sorbent

A new synthesized copolymer based on N-vinylimidazole-divinylbenzene (VIm-DVB) was tested as a sorbent for the solid-phase extraction (SPE) of polar analytes. In the on-line SPE, this synthesized sorbent enabled 100 ml of sample to be preconcentrated with recoveries as high as 80% for oxamyl, phenol (Ph) and derivates, bentazone and (4-chloro-2-methylphenoxy)acetic acid (MCPA). For the off-line SPE, 1000 ml of sample was extracted and recoveries were higher than 92% for all compounds with the exception of oxamyl (83%) and methomyl (78%). The VIm-DVB sorbent gives better recoveries than the previously synthesized 4-vinylpyridine-divinylbenzene (VP-DVB) resin and similar to such highly crosslinked commercial sorbents as LiChrolut EN or Oasis HLB. Real water samples were used to validate the on-line SPE method. Linearity was good and detection limits were between 0.1 and 0.2 microg l(-1).

Prediction of the behaviour of organic pollutants using cloud point extraction

A preconcentration study based on the cloud point phenomenon was carried out for a set of triazine herbicides, three of them chloro-substituted and three of them methylthio-substituted. Concentration factors and recoveries were calculated as function of the percentage of the non-ionic surfactant Triton X-114 employed. From these values, obtained from a cloud point extraction (CPE) procedure, the distribution coefficient between the Triton X-114 micelles and water, Kc, prior to CPE was calculated for each triazine and related to the corresponding octanol-water partition coefficient, Kow. In order to confirm the results obtained with the triazine herbicides, two sets of data from chemically different organic pollutants--organophosporous and chlorophenols--obtained from the literature were assessed, concluding that they display a similar behaviour to that of the triazine herbicides. This can be used to predict the CPE behaviour of other organic pollutants from their octanol-water partition coefficients. The Kc values were compared with the analyte concentration ratio in the surfactant-rich phase and aqueous phase (Ksa) with a view to obtaining a link between the analyte behaviour prior to and after cloud point extraction procedures.

A flow injection biosensor system for highly sensitive detection of 2,4,6-trichlorophenol based on preoxidation by ceric sulfate

A flow injection biosensor system was proposed for the highly sensitive detection of 2,4,6-trichlorophenol (2,4,6-TCP). The system is based on the preoxidation by ceric sulfate to the corresponding benzoquinone (2,6-dichloro-1,4-benzoquinone: 2,6-DC-1,4-BQ), which was characterized using cyclic voltammetry, hydrodynamic voltammetry, and UV-vis spectrophotometry. The laccase-based biosensor used in this analytical system responded sensitively to 2,4,6-TCP after the preoxidation by ceric sulfate. The response could be based on the bioelectrocatalytic recycling of oxidation product (2,6-DC-1,4-BQ) between laccase membrane and the electrode, because the oxidation product (2,6-DC-1,4-BQ) of 2,4,6-TCP was an electrochemically reversible redox species. The signal current was linearly related to the 2,4,6-TCP concentrations in a dynamic range of 2 nM - 2 microM; the slope and the y-intercept of the straight line were 1150 nA microM(-1) and 0.88 nA, respectively. The detection limit was 1.2 nM (S/N = 3) for a 20 microl injection. Among a variety of chlorophenols and some phenolic compounds, the only interferent was 2,4-dichlorophenol.

Solid-phase microextraction liquid chromatography/tandem mass spectrometry for the analysis of chlorophenols in environmental samples

Liquid chromatography with atmospheric pressure chemical ionisation mass spectrometry (LC/APCI-MS), using negative ion detection in a triple quadrupole instrument, was used for the determination of chlorophenols (CPs) in environmental samples. In-source collision-induced dissociation (CID) was compared with MS/MS fragmentation. In general, less fragmentation was observed in MS/MS as compared with in-source CID, with the latter providing more intense fragment ions due to chemical ionisation. Under MS/MS conditions [M - H - HCl](-) was the main fragment ion observed for all compounds except for pentachlorophenol, which showed no fragmentation. For multiple reaction monitoring (MRM) acquisition mode, the transition from [M - H](-) to [M - H - HCl](-) was selected, leading to detection limits down to 0.3 ng injected. Direct and headspace-solid-phase microextraction (HS-SPME) were used as preconcentration procedures for the analysis of CPs in wood and in industrially contaminated soils. CPs were quantified by standard addition, which led to good reproducibility (RSD between 4 and 11%) in both SIM and MRM modes, and detection limits down to ng/g. The combination of MS/MS and in-source CID allowed confirmation of the presence of CPs in environmental samples.

Oxidation of 4-chloro-3-methylphenol in pressurized hot water/supercritical water with potassium persulfate as oxidant

4-Chloro-3-methylphenol (c = 2.0 mM), representing a model pollutant, was oxidized in pressurized hot water and in supercritical water in a continuous flow system. Potassium persulfate was used as oxidant in concentrations of 8.0 and 40.0 mM. Contact times (reaction times) were 3-59 s, temperatures 110-390 degrees C, and pressures 235-310 bar. A wide temperature range was tested to determine the range over which potassium persulfate can be used effectively. Good oxidation efficiencies for 4-chloro-3-methylphenol were obtained at both oxidant concentrations and with short contact times at temperatures clearly underthe critical temperature of water; total organic carbon content of the effluent was low under optimized conditions. Corrosion, measured as nickel and chromium concentrations of the effluent, was more severe at oxidant concentration of 40.0 mM. Sulfate was present in the effluent in high concentrations. Sulfate is the limiting factor in the use of potassium persulfate in wastewater treatment and requires further water treatment.

Solid-phase microextraction coupled to liquid chromatography for the analysis of phenolic compounds in water

Solid-phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) has been applied to the analysis of priority pollutant phenolic compounds in water samples. Two types of polar fibers [50 microm Carbowax-templated resin (CW-TPR) and 60 microm polydimethylsiloxane-divinylbenzene (PDMS-DVB)] were evaluated. The effects of equilibration time and ionic strength of samples on the adsorption step were studied. The parameters affecting the desorption process, such as desorption mode, solvent composition and desorption time, were optimized. The developed method was used to determine the phenols in spiked river water samples collected in the Douro River, Portugal. Detection limits of 1-10 microg l(-1) were achieved under the optimized conditions.

Development of an automated on-line solid-phase extraction-high-performance liquid chromatographic method for the analysis of aniline, phenol, caffeine and various selected substituted aniline and phenol compounds in aqueous matrices

A fully automated solid-phase extraction (SPE)-high-performance liquid chromatographic method has been developed for the simultaneous analysis of substituted anilines and phenols in aqueous matrices at the low- to sub-microg/l level. Diode array and electrochemical detection operated in tandem mode were used for analyte detection. Two new polymeric sorbent materials (Hysphere-GP and Hysphere-SH) were evaluated for the on-line SPE of substituted anilines and phenols from aqueous matrices and their performance was compared with the PRP-1 and PLRP-S sorbents. Hysphere-GP sorbent packed in 10 x 2 mm cartridges was found to give better results in terms of sensitivity and selectivity of the overall analytical method. The proposed analytical method was validated for the analysis of these compounds in Axios river water that receives industrial, communal and agricultural wastes. The detection limits for all the compounds range between 0.05 and 0.2 microg/l, except for aniline and phenol which have detection limits of 0.5 and 1 microg/l, respectively (aniline detected by electrochemical detection). The recoveries for all the compounds are higher than 75% except for aniline (6%), phenol (50%) and 3-chlorophenol (67%). Finally, in order to evaluate the efficiency of the Hysphere-GP (10 x 2 mm) cartridges for sample stabilization and storage, the stability of the compounds of interest at the sorbed state onto these cartridges has been evaluated under three different temperature regimes (deep freeze, refrigeration, 20 degrees C).

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.

Chemically modified polymeric sorbents for sample preconcentration

Solid-phase extraction is an attractive alternative in sample preparation because it overcomes many drawbacks of liquid-liquid extraction and makes on-line determination possible by hyphenation with chromatographic techniques. Driven by the need for more effective and more selective sorbents, advances in solid-phase extraction include the development of new materials. This paper describes different types of chemically modified sorbents for the solid-phase extraction of compounds from aqueous samples. Chemical introduction of different functional groups into a polymeric resin improves the efficiency of solid-phase extraction by providing better surface contact with the aqueous samples; also, these sorbents have a greater capacity than the typical solid-phase materials for polar compounds have. The most important new sorbents are the chemically modified resins based on styrene-divinylbenzene copolymers. Preparation of these new sorbents is described, and advantages and drawbacks of off-line procedures and on-line procedures are also discussed. Applications for off-line and on-line chromatographic determinations of polar compounds are presented.

Cloud point preconcentration of rather polar compounds: application to the high-performance liquid chromatographic determination of priority pollutant chlorophenols

The potential of the cloud point methodology for the preconcentration of relatively polar compounds was studied using the non-ionic surfactant Triton X-114 and five EPA chlorophenols as test analytes. Analyte determination was performed using reversed-phase gradient LC with electrochemical and spectrophotometric detection. The amount of surfactant used is a critical variable in the preconcentration factor because it determines the extraction yield and the volume of surfactant-rich phase obtained. These values were determined as a function of the Triton X-114 concentration, together with the phase ratio, which allows prediction of the maximum preconcentration factor under given conditions.

Stability of sulfonated derivatives of benzene and naphthalene on disposable solid-phase extraction pre-columns and in an aqueous matrix

The stability of 14 sulfonated benzene and naphthalene compounds was investigated using polymeric solid-phase extraction cartridges, based on the styrene-divinylbenzene polymer Isolute ENV+. Several different storage conditions were tested to carry out the stability study in polymeric cartridges, which included storage at room temperature, at 4 degrees C and at -20 degrees C, during a period of up to 3 months. An additional stability study was carried out, not with the polymeric solid matrix, but in an aqueous matrix. This study was performed storing the samples at 4 degrees C, during 2 months under three different conditions: acidifying the water sample to pH 2.5-3 with sulfuric acid, adding 1% of formaldehyde (additive used in waste water analyses), and storing the water sample at 4 degrees C without any additives. The extraction of the SPE process is analyzed by ion-pair chromatography-electrospray mass spectrometry, in the negative ion mode. This study showed that the stability of polar aromatic sulfonic acids on disposable polymeric cartridges and in the water matrix is related to temperature and pH, respectively. Target aromatic sulfonated compounds stored in polymeric solid-phase extraction cartridges, are more stable at lower temperatures. The target analytes showed also good stability when stored in water at acidic pH. From the different analytes studied, substituted naphthalenesulfonates suffered more degradation than mononaphthalenesulfonates or benzenesulfonates under the experimental conditions of this work.

Solid-phase extraction for multiresidue analysis of organic contaminants in water

To overcome the limitations of the detection systems associated with gas or liquid chromatography, a sample pretreatment is required with the objective to provide a sample fraction enriched with all the target analytes and as free as possible from other matrix components. There is now no doubt that solid-phase extraction (SPE) has now become the method of choice for carrying out simultaneously the extraction and concentration of many compounds in aqueous samples. Many recent applications of SPE to multiresidue analysis are reviewed with an emphasis on the importance of the choice of the sorbent and of the sample volume. SPE is particularly well adapted to multiresidue analysis including compounds from a wide range of polarity or characterized by various physico-chemical properties. However, SPE is not completely free from practical problems inherent to the nature of the compounds or to the coupling to the chromatographic systems. Many examples are reported to illustrate these problems which can in most cases be circumvented. New developments in SPE are also reviewed.

Graphitized carbons for solid-phase extraction

The objective of this review is to provide updated information about the most important features of graphitized carbonaceous sorbents used for solid-phase extraction (SPE) of organic compounds from liquid natural matrices or extracts. The surface characteristics of graphitized carbon blacks and porous graphitic carbons are described which are responsible for the various types interactions (hydrophobic, electronic and ion-exchange) with analytes. The method development is given which is based on the prediction from liquid chromatographic retention data obtained using porous graphitic carbon. Emphasis is placed on their capability for trapping very polar and water-soluble analytes from aqueous samples. Comparison is made between carbon-based SPE sorbents and other reversed-phase materials such as octadecyl silicas and highly cross-linked copolymers. Especially, the difficulty encountered for the desorption of some strongly retained analytes is explained by LC data and solutions are given for optimizing the composition and volume of the desorption solution. Many examples illustrate the various common features of graphitized carbons which are the extraction of very polar analytes and multiresidue extractions. Some applications are specific to graphitized carbon black due to the presence of surface functional groups. They include the extraction of anionic compounds such as benzene and naphthalene sulfonates or acidic pesticides. Other applications are specific to porous graphitic carbon due to its flat and homogeneous surface. One example is the trace extraction of coplanar polychlorinated biphenyls (PCBs), dibenzo-p-dioxins and dibenzofurans from other PCB congeners.

Development of an immunochemical technique for the analysis of trichlorophenols using theoretical models

An immunoassay has been developed for trichlorophenol analysis on the basis of theoretical chemistry modeling studies. These data have allowed us to choose the optimum chemical structure of the immunizing hapten according to realistic similarities with the target analyte. The synthesis of this hapten and the subsequent application of an appropriate immunization protocol have lead to the production of polyclonal antibodies against the target analyte. A homologous direct competitive ELISA has been developed that can be carried out in about 1 h. It has a limit of detection of 0.2 +/- 0.06 microg/L (1.01 +/- 0.3 nM) and it has been proven to tolerate a wide range of ionic strengths and pH values. Thus, the assay has acceptable features in samples with ionic strength between 4 and 56 mS/cm and pH values between 5.5 and 9.5. Studies on the selectivity of this immunoassay have demonstrated a high recognition of the corresponding brominated analogues. Other phenolic compounds do not interfere significantly in the analysis of 2,4,6-trichorophenol using this immunochemical technique. The accuracy of the assay has been evaluated using certified and spiked samples.

Simultaneous quantitative trace analysis of anionic and nonionic surfactant mixtures by reversed-phase liquid chromatography

The aim of this work was to simultaneously analyse mixtures of a polydisperse polyethylene oxide (PEO) nonionic surfactant and an anionic surfactant (sodium dodecylsulphate, SDS) in water containing sodium chloride in order to quantify trace amounts of these mixtures after their adsorption at water-solid interfaces. A fractional factorial design was then used to optimise the separation by ion-pair reversed-phase liquid chromatography as a function of six factors: the chain length of the tetraalkylammonium salt used as ion-pairing reagent which varied from methyl (C1) to n-propyl (C3); the concentration of this ion-pairing salt; the acetonitrile percentage in water used as organic modifier; the flow-rate; the temperature of analysis and also the sodium chloride concentration. The factorial design enabled in a limited number of analyses, not only to determine which factors had significant effects on retention times or on resolution between a pair of nonionic oligomers, but also to modelize and then find the interesting and rugged area where this resolution was optimal as well as the conditions where time of analysis was not prohibitive. After optimisation of HPLC analysis, we used a trace enrichment procedure to quantify very low concentrations of SDS and C12E9 polydisperse PEO in water. A C18 cartridge and a strong anionic exchange cartridge were coupled and the conditions of elution were optimised in order to obtain concentrated samples which were injected in the same eluent than the HPLC mobile phase. Under such conditions, we were able to quantify, in a single run, mixtures of anionic and nonionic surfactants at concentrations as low as 3.6 microg l(-1) for SDS and 2.5 microg l(-1) for each PEO oligomer in water.