Zoraida Sosa-Ferrera | Universidad de Las Palmas de Gran Canaria (original) (raw)

Papers by Zoraida Sosa-Ferrera

VIIIth International Symposium on Luminescence Spectrometry in Biomedical and Environmental - Detection Techniques and Applications in Chromatography and Capillary Electrophoresis may 26-29, 1998, University of Las Palmas de Gran Canaria, Canary Islands, Spain: Abstracts of invited lectures, oral..., 1998

Journal of Liquid Chromatography & Related Technologies, 2002

The effects of extraction parameters on the microwave-assisted extraction (MAE) of polychlorinate... more The effects of extraction parameters on the microwave-assisted extraction (MAE) of polychlorinated biphenyls (PCBs) and polychlorinated dibenzodioxins (PCDDs) from fly ash were compared. The effects of toluene-isopropyl alcohol (IPA) mixture compositions, solvent volume, temperature, extraction time (rise and hold time), and microwave power on the variation of recoveries were studied. The MAE carried out at 100°C for 35.3 min using 5 mL of toluene-IPA (90 : 10, v/v) was more effective in isolating PCBs and PCDDs from fly ash. Multi-layer column chromatography on neutral and acidic silica gel with n-hexane was used for cleaning up the extracts. High performance liquid chromatography (HPLC) with ultraviolet (UV) detection was employed to identify and quantify the analytes.

Global NEST International Conference on Environmental Science & Technology

Microplastics (MPs) are pollutants of emerging concern. These small particles are found throughou... more Microplastics (MPs) are pollutants of emerging concern. These small particles are found throughout the world. Its best-known negative effects are that they can confuse marine organisms that would feed on them, or block their airways. In addition, they have been shown to act as vectors of contamination too. In this work, a methodology for the extraction of ten widely used pharmaceutical compounds adsorbed into MPs has been developed. This methodology is based on Ultrasound Assisted Extraction (UAE) followed by Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry (UHPLC-MS/MS). In the optimal conditions, Limits of Detection (LODs) between 0.25 and 15.8 ng·g-1 were obtained. The optimized method was successfully applied to different MPs samples taken from three beaches of Canary Islands. The results indicated the detection of all target pharmaceuticals at least one time in the analysed samples.

Analytical and Bioanalytical Chemistry, 2009

An analytical methodology based on an on-line sample enrichment of water samples by means of an i... more An analytical methodology based on an on-line sample enrichment of water samples by means of an imprinted polymer, and the separation of benzimidazole compounds within a C 18 column by ion-pair reversed-phase liquid chromatography, has been developed. The molecularly imprinted polymer has been synthesized by precipitation polymerization using thiabendazole as template molecule, methacrylic acid as functional monomer, and divinylbenzene as cross-linker. Initial experiments carried out by solid-phase extraction on cartridges demonstrated a clear imprint effect for thiabendazole, as well as the ability of the imprinted polymer to selectively rebind several benzimidazole compounds. The developed methodology has been applied to the quantification of thiabendazole, carbendazim, and benomyl in river, tap, and well water samples within a single analytical run at concentration levels below the legislated maximum concentration levels. In this sense, detection limits of 2.3-5.7 ng•L −1 have been obtained for the analysis of benzimidazole fungicides in different water matrices. Recoveries obtained for the determination of benzimidazole fungicides in spiked samples ranged from 87% to 95%, with RSD below 5% in all cases.

Science of The Total Environment, Jun 1, 2023

Environmental Pollution, Oct 1, 2023

Water Air and Soil Pollution, Feb 26, 2013

ABSTRACT A new analytical methodology based on ultra high performance liquid chromatography (UHPL... more ABSTRACT A new analytical methodology based on ultra high performance liquid chromatography (UHPLC) after microwave assisted extraction, followed by a clean-up and preconcentration step with solid phase extraction (MAE–SPE) has been developed for the simultaneous determination of 11 endocrine-disrupting compounds (EDCs), including alkylphenolic compounds, bisphenol A, and various synthetic and natural steroidal hormones, in sewage sludge samples. The effects of different variables on MAE-SPE were studied and optimised. The recoveries obtained were higher than 77 %, whereas the relative standard deviations were less than 9 %. The detection limits ranged between 0.1 and 0.7 ng g−1. The developed methodology was successfully applied to the assessment of the presence of EDCs to sewage sludge samples that were collected bimonthly during 1 year and a half from two wastewater treatment plants (WWTPs) located in Las Palmas de Gran Canaria (Canary Islands, Spain). All compounds were consistently found in all the samples under study.

Journal of AOAC International, 2002

Microwave-assisted extraction methodology is used to extract different compounds from various kin... more Microwave-assisted extraction methodology is used to extract different compounds from various kinds of marine solid samples, such as soils, sediments, and organisms. A new analytical method was developed to extract polychlorinated biphenyls and polychlorinated dibenzofurans by using a conventional microwave system and the nonionic surfactant, polyoxyethylene 10 lauryl ether as the extractant as a prior step to liquid chromatography analysis coupled with fluorescence detection. The method was applied to the extraction and determination of these analytes in samples of blue mussels (Mytilus galloprovincialis), cockles (Cerastoderma edule), and clams (Dosinia exoleta). Compared with the traditional Soxhlet extraction, results of the proposed method showed acceptable recovery percentages for the organochlorinated compounds under study and standard deviation values <10%.

Talanta, Sep 1, 2011

In this work, we present the development and application of a microwave assisted extraction follo... more In this work, we present the development and application of a microwave assisted extraction followed by liquid chromatography-tandem mass spectrometry methodology (MAE-LC-MS/MS) for the determination of various estradiol-mimicking compounds in sewage sludge samples. For the purification of the MAE extracts, we have employed a solid phase extraction (SPE) clean-up procedure, previously optimised. The entire method provides recoveries between 71.7% and 103.1%, with relative standard deviation lower than 11.1% and limits of detection ranging from 0.6 to 3.5 ng g −1. The developed method was applied to samples from three wastewater treatment plants (WWTPs) located in Las Palmas of Gran Canaria (Spain), two of which had a conventional activated sludge treatment (AST), whereas the third treatment plant had an advanced membrane bioreactor treatment (MBR). All of the analytes in the study, including (nonylphenol (NP), octylphenol (OP), and some of their ethoxylated chains AP n EOs (n ≤ 7), 17␤-estradiol (E2), estriol (E3), 17␣-ethynylestradiol (EE) and bisphenol-A (BPA)), were found in almost all samples in concentrations ranging from 0.9 to 710.2 ng g −1 .

Journal of Chromatography A, Jun 1, 2005

A new methodology based on the microwave assisted micellar extraction (MAME) technique has been o... more A new methodology based on the microwave assisted micellar extraction (MAME) technique has been optimised, using soil samples, to extract and determine a mixture of the eight organophosphorous pesticides mainly used in agriculture. The pesticides under study have been extracted using the non-ionic surfactants polyoxyethylene 10 lauryl ether (POLE) and oligoethylene glycol monoalkyl ether (Genapol X-080). The optimal extraction variables, such as surfactant concentration, pH, radiation time and microwave power were determined for each surfactant. The results show the advantage of using POLE instead of Genapol X-080 for the extraction of the organophosphorus pesticides with recoveries higher than 70% for most of the compounds and relative standard deviations (RSD) below 2.6%. This method was successfully applied to fresh samples as well as to aged samples for the analysis of soils with different characteristics and compared with the traditional Soxhlet technique.

Science of The Total Environment, Dec 1, 2017

Twenty-three pharmaceuticals were monitoring in sewage from WWTPs. • Simplified SPE-LC-MS/MS was ... more Twenty-three pharmaceuticals were monitoring in sewage from WWTPs. • Simplified SPE-LC-MS/MS was employed to analyse pharmaceuticals from sewage samples. • Removal efficiencies of pharmaceuticals from two different WWTPs were evaluated. • Environmental risk assessment of pharmaceuticals was determined.

Journal of Chromatography B, Mar 1, 2019

Cytostatic drugs are compounds used to fight cancer, which may be excreted after administration t... more Cytostatic drugs are compounds used to fight cancer, which may be excreted after administration to patients, and eventually reach wastewater. Given the high incidence of cancer and the properties of drugs, the drug concentrations in water systems should be evaluated. We present the optimization, development and application of a solid phase extraction (SPE) method for the determination of eight cytostatic compounds of different classes in wastewater and seawater samples. We compared four SPE cartridges prior to their determination by Ultra-High Performance Liquid Chromatography tandem Mass Spectrometry. For wastewater samples, the Oasis HLB cartridge gave the best recoveries, which were higher than 65% in most cases, achieving limit of detections (LODs) of 1.68-103.95 ng·L-1. In seawater samples, the Bond Elut cartridge afforded the best recoveries >70%, with LODs of 0.95-5.14 ng·L-1. The optimal procedure was applied in four hospital wastewater effluent samples taken during one year, and in different influents and effluents from wastewater treatment plants and seawater from marine outfalls taken in eight campaigns during two years, in Gran Canaria island (Spain). Results showed that etoposide was present in influents of wastewater treatment plants in several months and different wastewater treatment plants and hospital effluents in the range 375.8-5141 ng·L-1, while cyclophosphamide was present in some months in effluents from only one wastewater treatment plant and hospital effluents in the range 55.94-1212 ng·L-1. Vinblastine and vincristine were detected in one sample of hospital at concentrations of 1836 ng·L-1 and 1851 ng·L-1, respectively.

Journal of Hazardous Materials, Nov 1, 2010

Recently, many chemicals released into the environment have been shown to mimic endogenous hormon... more Recently, many chemicals released into the environment have been shown to mimic endogenous hormones such as estradiol. It has been demonstrated that these compounds cause several adverse effects on wildlife and humans, such as the feminization of animal species, development of physical abnormalities and birth defects, and reproductive failure. In an effort to model the behaviour of some endocrine-disrupting chemicals (EDCs) and to establish the level of contamination in sewage samples, a quantitative method for the simultaneous determination of nonylphenol, octylphenol and corresponding ethoxylates (1-12), 17α-ethynylestradiol, bisphenol-A, and 17β-estradiol and two of its metabolites have been developed. Identification and quantification were achieved by high performance liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS). Satisfactory detection limits (between 0.5-6 ng L(-1) in the dissolved phase and 1.4-12.7 ng g(-1) in the particulate phase) and analyte recoveries (between 60% and 108%) were achieved for target compounds. The optimised method was applied to the determination of EDCs in liquid sewage samples collected from a wastewater treatment plant (WWTP) in Las Palmas de Gran Canaria (Spain). Concentrations of EDCs ranged from &amp;amp;amp;amp;lt;10 ng L(-1) to nearly 1200 ng L(-1) in the dissolved phase, and from 0.005 μg g(-1) to 2.8 μg g(-1) in the suspended particulate matter.

Food and Chemical Toxicology, May 1, 2023

Proceedings of the 17th International Conference on Environmental Science and Technology, Nov 21, 2022

Microplastics (MPs) are pollutants of emerging concern. These small particles are found throughou... more Microplastics (MPs) are pollutants of emerging concern. These small particles are found throughout the world. Its best-known negative effects are that they can confuse marine organisms that would feed on them, or block their airways. In addition, they have been shown to act as vectors of contamination too. In this work, a methodology for the extraction of ten widely used pharmaceutical compounds adsorbed into MPs has been developed. This methodology is based on Ultrasound Assisted Extraction (UAE) followed by Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry (UHPLC-MS/MS). In the optimal conditions, Limits of Detection (LODs) between 0.25 and 15.8 ng•g-1 were obtained. The optimized method was successfully applied to different MPs samples taken from three beaches of Canary Islands. The results indicated the detection of all target pharmaceuticals at least one time in the analysed samples.

Analytical and Bioanalytical Chemistry, Jul 28, 2006

A solid-phase microextraction (SPME) procedure using two commercial fibers coupled with high-perf... more A solid-phase microextraction (SPME) procedure using two commercial fibers coupled with high-performance liquid chromatography (HPLC) is presented for the extraction and determination of organochlorine pesticides in water samples. We have evaluated the extraction efficiency of this kind of compound using two different fibers: 60-mum polydimethylsiloxane-divinylbenzene (PDMS-DVB) and Carbowax/TPR-100 (CW/TPR). Parameters involved in the extraction and desorption procedures (e.g. extraction time, ionic strength, extraction temperature, desorption and soaking time) were studied and optimized to achieve the maximum efficiency. Results indicate that both PDMS-DVB and CW/TPR fibers are suitable for the extraction of this type of compound, and a simple calibration curve method based on simple aqueous standards can be used. All the correlation coefficients were better than 0.9950, and the RSDs ranged from 7% to 13% for 60-mum PDMS-DVB fiber and from 3% to 10% for CW/TPR fiber. Optimized procedures were applied to the determination of a mixture of six organochlorine pesticides in environmental liquid samples (sea, sewage and ground waters), employing HPLC with UV-diode array detector.

VIIIth International Symposium on Luminescence Spectrometry in Biomedical and Environmental - Detection Techniques and Applications in Chromatography and Capillary Electrophoresis may 26-29, 1998, University of Las Palmas de Gran Canaria, Canary Islands, Spain: Abstracts of invited lectures, oral..., 1998

Journal of Liquid Chromatography & Related Technologies, 2002

The effects of extraction parameters on the microwave-assisted extraction (MAE) of polychlorinate... more The effects of extraction parameters on the microwave-assisted extraction (MAE) of polychlorinated biphenyls (PCBs) and polychlorinated dibenzodioxins (PCDDs) from fly ash were compared. The effects of toluene-isopropyl alcohol (IPA) mixture compositions, solvent volume, temperature, extraction time (rise and hold time), and microwave power on the variation of recoveries were studied. The MAE carried out at 100°C for 35.3 min using 5 mL of toluene-IPA (90 : 10, v/v) was more effective in isolating PCBs and PCDDs from fly ash. Multi-layer column chromatography on neutral and acidic silica gel with n-hexane was used for cleaning up the extracts. High performance liquid chromatography (HPLC) with ultraviolet (UV) detection was employed to identify and quantify the analytes.

Global NEST International Conference on Environmental Science & Technology

Microplastics (MPs) are pollutants of emerging concern. These small particles are found throughou... more Microplastics (MPs) are pollutants of emerging concern. These small particles are found throughout the world. Its best-known negative effects are that they can confuse marine organisms that would feed on them, or block their airways. In addition, they have been shown to act as vectors of contamination too. In this work, a methodology for the extraction of ten widely used pharmaceutical compounds adsorbed into MPs has been developed. This methodology is based on Ultrasound Assisted Extraction (UAE) followed by Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry (UHPLC-MS/MS). In the optimal conditions, Limits of Detection (LODs) between 0.25 and 15.8 ng·g-1 were obtained. The optimized method was successfully applied to different MPs samples taken from three beaches of Canary Islands. The results indicated the detection of all target pharmaceuticals at least one time in the analysed samples.

Analytical and Bioanalytical Chemistry, 2009

An analytical methodology based on an on-line sample enrichment of water samples by means of an i... more An analytical methodology based on an on-line sample enrichment of water samples by means of an imprinted polymer, and the separation of benzimidazole compounds within a C 18 column by ion-pair reversed-phase liquid chromatography, has been developed. The molecularly imprinted polymer has been synthesized by precipitation polymerization using thiabendazole as template molecule, methacrylic acid as functional monomer, and divinylbenzene as cross-linker. Initial experiments carried out by solid-phase extraction on cartridges demonstrated a clear imprint effect for thiabendazole, as well as the ability of the imprinted polymer to selectively rebind several benzimidazole compounds. The developed methodology has been applied to the quantification of thiabendazole, carbendazim, and benomyl in river, tap, and well water samples within a single analytical run at concentration levels below the legislated maximum concentration levels. In this sense, detection limits of 2.3-5.7 ng•L −1 have been obtained for the analysis of benzimidazole fungicides in different water matrices. Recoveries obtained for the determination of benzimidazole fungicides in spiked samples ranged from 87% to 95%, with RSD below 5% in all cases.

Science of The Total Environment, Jun 1, 2023

Environmental Pollution, Oct 1, 2023

Water Air and Soil Pollution, Feb 26, 2013

ABSTRACT A new analytical methodology based on ultra high performance liquid chromatography (UHPL... more ABSTRACT A new analytical methodology based on ultra high performance liquid chromatography (UHPLC) after microwave assisted extraction, followed by a clean-up and preconcentration step with solid phase extraction (MAE–SPE) has been developed for the simultaneous determination of 11 endocrine-disrupting compounds (EDCs), including alkylphenolic compounds, bisphenol A, and various synthetic and natural steroidal hormones, in sewage sludge samples. The effects of different variables on MAE-SPE were studied and optimised. The recoveries obtained were higher than 77 %, whereas the relative standard deviations were less than 9 %. The detection limits ranged between 0.1 and 0.7 ng g−1. The developed methodology was successfully applied to the assessment of the presence of EDCs to sewage sludge samples that were collected bimonthly during 1 year and a half from two wastewater treatment plants (WWTPs) located in Las Palmas de Gran Canaria (Canary Islands, Spain). All compounds were consistently found in all the samples under study.

Journal of AOAC International, 2002

Microwave-assisted extraction methodology is used to extract different compounds from various kin... more Microwave-assisted extraction methodology is used to extract different compounds from various kinds of marine solid samples, such as soils, sediments, and organisms. A new analytical method was developed to extract polychlorinated biphenyls and polychlorinated dibenzofurans by using a conventional microwave system and the nonionic surfactant, polyoxyethylene 10 lauryl ether as the extractant as a prior step to liquid chromatography analysis coupled with fluorescence detection. The method was applied to the extraction and determination of these analytes in samples of blue mussels (Mytilus galloprovincialis), cockles (Cerastoderma edule), and clams (Dosinia exoleta). Compared with the traditional Soxhlet extraction, results of the proposed method showed acceptable recovery percentages for the organochlorinated compounds under study and standard deviation values <10%.

Talanta, Sep 1, 2011

In this work, we present the development and application of a microwave assisted extraction follo... more In this work, we present the development and application of a microwave assisted extraction followed by liquid chromatography-tandem mass spectrometry methodology (MAE-LC-MS/MS) for the determination of various estradiol-mimicking compounds in sewage sludge samples. For the purification of the MAE extracts, we have employed a solid phase extraction (SPE) clean-up procedure, previously optimised. The entire method provides recoveries between 71.7% and 103.1%, with relative standard deviation lower than 11.1% and limits of detection ranging from 0.6 to 3.5 ng g −1. The developed method was applied to samples from three wastewater treatment plants (WWTPs) located in Las Palmas of Gran Canaria (Spain), two of which had a conventional activated sludge treatment (AST), whereas the third treatment plant had an advanced membrane bioreactor treatment (MBR). All of the analytes in the study, including (nonylphenol (NP), octylphenol (OP), and some of their ethoxylated chains AP n EOs (n ≤ 7), 17␤-estradiol (E2), estriol (E3), 17␣-ethynylestradiol (EE) and bisphenol-A (BPA)), were found in almost all samples in concentrations ranging from 0.9 to 710.2 ng g −1 .

Journal of Chromatography A, Jun 1, 2005

A new methodology based on the microwave assisted micellar extraction (MAME) technique has been o... more A new methodology based on the microwave assisted micellar extraction (MAME) technique has been optimised, using soil samples, to extract and determine a mixture of the eight organophosphorous pesticides mainly used in agriculture. The pesticides under study have been extracted using the non-ionic surfactants polyoxyethylene 10 lauryl ether (POLE) and oligoethylene glycol monoalkyl ether (Genapol X-080). The optimal extraction variables, such as surfactant concentration, pH, radiation time and microwave power were determined for each surfactant. The results show the advantage of using POLE instead of Genapol X-080 for the extraction of the organophosphorus pesticides with recoveries higher than 70% for most of the compounds and relative standard deviations (RSD) below 2.6%. This method was successfully applied to fresh samples as well as to aged samples for the analysis of soils with different characteristics and compared with the traditional Soxhlet technique.

Science of The Total Environment, Dec 1, 2017

Twenty-three pharmaceuticals were monitoring in sewage from WWTPs. • Simplified SPE-LC-MS/MS was ... more Twenty-three pharmaceuticals were monitoring in sewage from WWTPs. • Simplified SPE-LC-MS/MS was employed to analyse pharmaceuticals from sewage samples. • Removal efficiencies of pharmaceuticals from two different WWTPs were evaluated. • Environmental risk assessment of pharmaceuticals was determined.

Journal of Chromatography B, Mar 1, 2019

Cytostatic drugs are compounds used to fight cancer, which may be excreted after administration t... more Cytostatic drugs are compounds used to fight cancer, which may be excreted after administration to patients, and eventually reach wastewater. Given the high incidence of cancer and the properties of drugs, the drug concentrations in water systems should be evaluated. We present the optimization, development and application of a solid phase extraction (SPE) method for the determination of eight cytostatic compounds of different classes in wastewater and seawater samples. We compared four SPE cartridges prior to their determination by Ultra-High Performance Liquid Chromatography tandem Mass Spectrometry. For wastewater samples, the Oasis HLB cartridge gave the best recoveries, which were higher than 65% in most cases, achieving limit of detections (LODs) of 1.68-103.95 ng·L-1. In seawater samples, the Bond Elut cartridge afforded the best recoveries >70%, with LODs of 0.95-5.14 ng·L-1. The optimal procedure was applied in four hospital wastewater effluent samples taken during one year, and in different influents and effluents from wastewater treatment plants and seawater from marine outfalls taken in eight campaigns during two years, in Gran Canaria island (Spain). Results showed that etoposide was present in influents of wastewater treatment plants in several months and different wastewater treatment plants and hospital effluents in the range 375.8-5141 ng·L-1, while cyclophosphamide was present in some months in effluents from only one wastewater treatment plant and hospital effluents in the range 55.94-1212 ng·L-1. Vinblastine and vincristine were detected in one sample of hospital at concentrations of 1836 ng·L-1 and 1851 ng·L-1, respectively.

Journal of Hazardous Materials, Nov 1, 2010

Recently, many chemicals released into the environment have been shown to mimic endogenous hormon... more Recently, many chemicals released into the environment have been shown to mimic endogenous hormones such as estradiol. It has been demonstrated that these compounds cause several adverse effects on wildlife and humans, such as the feminization of animal species, development of physical abnormalities and birth defects, and reproductive failure. In an effort to model the behaviour of some endocrine-disrupting chemicals (EDCs) and to establish the level of contamination in sewage samples, a quantitative method for the simultaneous determination of nonylphenol, octylphenol and corresponding ethoxylates (1-12), 17α-ethynylestradiol, bisphenol-A, and 17β-estradiol and two of its metabolites have been developed. Identification and quantification were achieved by high performance liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS). Satisfactory detection limits (between 0.5-6 ng L(-1) in the dissolved phase and 1.4-12.7 ng g(-1) in the particulate phase) and analyte recoveries (between 60% and 108%) were achieved for target compounds. The optimised method was applied to the determination of EDCs in liquid sewage samples collected from a wastewater treatment plant (WWTP) in Las Palmas de Gran Canaria (Spain). Concentrations of EDCs ranged from &amp;amp;amp;amp;lt;10 ng L(-1) to nearly 1200 ng L(-1) in the dissolved phase, and from 0.005 μg g(-1) to 2.8 μg g(-1) in the suspended particulate matter.

Food and Chemical Toxicology, May 1, 2023

Proceedings of the 17th International Conference on Environmental Science and Technology, Nov 21, 2022

Microplastics (MPs) are pollutants of emerging concern. These small particles are found throughou... more Microplastics (MPs) are pollutants of emerging concern. These small particles are found throughout the world. Its best-known negative effects are that they can confuse marine organisms that would feed on them, or block their airways. In addition, they have been shown to act as vectors of contamination too. In this work, a methodology for the extraction of ten widely used pharmaceutical compounds adsorbed into MPs has been developed. This methodology is based on Ultrasound Assisted Extraction (UAE) followed by Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry (UHPLC-MS/MS). In the optimal conditions, Limits of Detection (LODs) between 0.25 and 15.8 ng•g-1 were obtained. The optimized method was successfully applied to different MPs samples taken from three beaches of Canary Islands. The results indicated the detection of all target pharmaceuticals at least one time in the analysed samples.

Analytical and Bioanalytical Chemistry, Jul 28, 2006

A solid-phase microextraction (SPME) procedure using two commercial fibers coupled with high-perf... more A solid-phase microextraction (SPME) procedure using two commercial fibers coupled with high-performance liquid chromatography (HPLC) is presented for the extraction and determination of organochlorine pesticides in water samples. We have evaluated the extraction efficiency of this kind of compound using two different fibers: 60-mum polydimethylsiloxane-divinylbenzene (PDMS-DVB) and Carbowax/TPR-100 (CW/TPR). Parameters involved in the extraction and desorption procedures (e.g. extraction time, ionic strength, extraction temperature, desorption and soaking time) were studied and optimized to achieve the maximum efficiency. Results indicate that both PDMS-DVB and CW/TPR fibers are suitable for the extraction of this type of compound, and a simple calibration curve method based on simple aqueous standards can be used. All the correlation coefficients were better than 0.9950, and the RSDs ranged from 7% to 13% for 60-mum PDMS-DVB fiber and from 3% to 10% for CW/TPR fiber. Optimized procedures were applied to the determination of a mixture of six organochlorine pesticides in environmental liquid samples (sea, sewage and ground waters), employing HPLC with UV-diode array detector.