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ABSTRACT: A dynamic ultrasound-assisted extraction (UAE) of marine sediments has been optimized using experimental design methodology. Comprehensive two-dimensional gas chromatography (GC x GC) using a cryogenic modulator, and time-of-flight-mass spectrometry (TOF-MS) were used to separate and identify environmental pollutants. Six compounds from three different chemical classes were used to optimize the extraction parameters.
Journal of Chromatography 10/2005; 1086(1-2):122-7. · 4.53 Impact Factor
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ABSTRACT: An extraction method based on the use of a focused microwave-assisted Soxhlet extractor with subsequent gas chromatography separation and mass spectrometry detection is proposed for the analysis of environmental pollutants from marine sediments collected at the outflow of an urban wastewater treatment plant to the sea. For the extraction of compounds with different polarity, sequential extraction with dichloromethane and water was performed on each sample. The experimental variables were optimized by the experimental design methodology for both the organic and aqueous extractant. The total time required for quantitative extraction of triclosan, bisphenol A, estrone, estradiol, oxyfluorofen and permethrin was 75 min, a short time as compared with the 24 h Soxhlet extraction (diethylstilbestrol, 4-octylphenol, procymidone and 2,7/2,8-dichlorodibenzo-p-dioxin isomer pair).
Chromatographia 06/2005; 62(1):69-74. · 1.20 Impact Factor
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ABSTRACT: A dynamic ultrasound-assisted extraction (UAE) method with on-line pre-column derivatization/high performance liquid chromatography (HPLC) and fluorimetric detection is proposed for the analysis of colistin in feed. A flow injection manifold is used for the development of the extraction and derivatization steps and for interfacing them with the separation/detection step, thus providing an on-line approach with the advantage of minimum sample handling. The derivatization was performed with ortho-phthaldialdehyde and 2-mercaptoethanol. The optimum conditions for colistin extraction and formation of the fluorescent derivative have been obtained by experimental design methodology. The use of a high-intensity probe sonication makes UAE an expeditious (7 min versus > 1 h) and efficient (93.1-98.2% versus 87.5-94% of recovery) alternative as compared with extraction using an ultrasonic bath. The within-laboratory reproducibility and repeatability, expressed as percentage of relative standard deviation, were 5.2 and 5.8, respectively.
Journal of Chromatography 02/2005; 1066(1-2):1-7. · 4.53 Impact Factor
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ABSTRACT: An automated screening approach for fluoroquinolone (FQ) antibiotics (norfloxacin and ciprofloxacin) in soil samples has been developed. The proposed approach consists on dynamic microwave-assisted extraction and subsequent real-time on-line monitoring of the analytes extracted; thus, the extraction is halted when complete leaching of the analytes has been reached (independently of the sample matrix), avoiding extraction times in excess. The end of the extraction allowed quantifying the total content of the analytes. The extraction was carried out using pure water as extractant and consisted of a number of extraction cycles (depending on the sample matrix) in which the sample was subjected to microwave irradiation while the direction of the extractant was changed in an iterative manner. The target analytes were fluorometrically monitored after derivatization with a terbium (Tb3+)/tri-n-octylphosphine oxide (TOPO)/cetylpyridinium chloride (CPCl)/acetate buffer solution. Optimum conditions for analytes extraction and formation of FQ-Tb3+-TOPO ternary complexes have been obtained using the experimental design methodology. The mean recoveries from soil samples spiked with 5 and 0.5 microg/g of each analyte were (95.2+/-4.16%) and (98+/-5.21%), respectively. The within-laboratory reproducibility and repeatability, expressed as relative standard deviation, were 7.29 and 5.80%, respectively. The approach only allows monitoring of the overall content of the species that yield fluorescent complexes with the derivatizing reagent, so the use of chromatography is mandatory for individual separation/quantification of the target compounds.
Journal of Chromatography 01/2005; 1059(1-2):25-31. · 4.53 Impact Factor
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ABSTRACT: Modified pressurised hot water is used for the development of a high pressure liquid-liquid extraction method for the decontamination of used industrial oils from inorganic non-metal species (chlorine, fluorine and sulphur). The oils were subjected to dynamic extraction with water modified with 5% v/v HNO3 at 200 degrees C as extractant. Under these working conditions the analytes were transferred to the aqueous phase. Spontaneous separation of the two immiscible liquid phases (the used oil and extract) takes place in the collection flask after extraction. The treated and untreated oil samples were oxidised and the chloride, fluoride and sulphate thus formed were determined by ion-chromatography. The method was applied to four oil samples from different locations in Spain. A residence time of approximately =10 min provided oil samples from which 88.3%, 89.4% and 89.4% of chloride, fluoride and sulphate, respectively, have been removed with respect to the initial concentration of each analyte in the oil. The repeatability, expressed as relative standard deviation (RSD), was of 11.9%, 13.7% and 7.2% for Cl(-), F(-) and SO4(2-), respectively; whilst the within-laboratory reproducibility yielded RSDs of 6.2%, 7.9% and 6.2% for the same analytes. The proposed approach has proved to be efficient, simple, easily transferable to industrial scale, cheap, fast and environmentally friendly.
Chemosphere 10/2004; 56(10):943-7. · 3.21 Impact Factor
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ABSTRACT: An approach based on continuous pressurized liquid-liquid extraction with 20% HNO(3)/1M KCl/10(-3)M EDTA as extractant has been developed for the extraction of metals from the oil resulting from recycled tires. A multivariate optimization of the main variables affecting the extraction process has been performed. The method has been applied to three oil samples with different contents in V, Ni, Zn, Fe and Cu. The target metals have been determined in both untreated and treated oil by flame atomic absorption spectrometry (FAAS) in order to obtain the extraction efficiency. Under the optimum conditions, recoveries higher than 90% have been obtained with a repeatability and within-laboratory reproducibility, expressed as relative standard deviations, ranging from 2.75 to 6.91 and 2.97 to 8.16%, respectively. For applications where the demetalization does not require being complete, a study of the demetalization degree achieved depending on the extraction temperature and extractant composition has also been performed. This study provides useful data about the cheapest working conditions to be used in order to obtain a given demetalization level.
Talanta 06/2004; 63(2):391-6. · 3.79 Impact Factor
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ABSTRACT: A screening method for linear alkylbenzene sulfonates (LAS) in sediments has been developed. Soxhlet extraction with water assisted by focused microwaves provides recoveries better (>90%) than obtained by conventional Soxhlet extraction (70-80%). Coupling of the extractor with an on-line preconcentration/derivatization/detection manifold through a flow injection (FI) interface allows a fully automated screening approach. A yes/no answer can be obtained in less than 2 h (for the whole analytical process), a short time compared with the at least 24 h of Soxhlet extraction (without final detection). Due to the use of water as leaching agent, the proposed method is environmentally friendly.
Journal of Chromatography 02/2004; 1026(1-2):41-6. · 4.53 Impact Factor
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ABSTRACT: The coupling of a static pressurized liquid extractor to a flow injection manifold has allowed real-time on-line fluorescence monitoring of the polycyclic aromatic hydrocarbons (PAHs) extracted from environmental solid samples, which can be used for either screening or semiquantitative purposes. Sodium dodecyl sulfate (SDS) was added to the water for favoring the extraction of the low-polar analytes. Different solid samples such as sandy soil, river sediments, trout and sardine spiked with the target PAHs were subjected to several 15-min static extraction cycles with SDS-water, at 200 degrees C. The results obtained demonstrated that fluorometric monitoring of static pressurized liquid extraction constitutes an approach as efficient as conventional Soxhlet for the extraction of PAHs from solid samples but with the following positive features: (a) drastic reduction of the extraction time as the extraction kinetics can be monitored and thus the end of the leaching step determined independently of the sample matrix; (b) use of water as extractant thus given place to an environmentally friendly method; and (c) coupling of static extraction to subsequent dynamic steps. The method has been applied to a certified reference material (CRM 524, BCR, industrial soil/organics) for quality assurance/validation. The total content of each analyte was determined by HPLC-fluorimetric detection.
Journal of Chromatography 12/2002; 978(1-2):49-57. · 4.53 Impact Factor
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ABSTRACT: A comparison of the feasibility of the three operational modes of pressurized hot solvent extraction (PHSE) (namely, static, where a fixed extractant volume is used; dynamic, where the extractant continually flows through the sample; and static-dynamic mode, which consists of a combination of the two previous modes) for the extraction of polycyclic aromatic hydrocarbons (PAHs) from environmental solid samples (such as soil, sediment, trout, and sardine) has been performed. In all cases, a sodium dodecyl sulfate (SDS) aqueous solution was used as leaching agent. The use of a flow injection manifold between the extractor and a molecular fluorescence detector allowed real-time on-line fluorescence monitoring of the PAHs extracted from the samples, thus working as a screening system and providing qualitative and semiquantitative information on the target analytes extracted from both natural and spiked samples. The on-line monitoring option allowed the extraction kinetics to be monitored and the end of the leaching step to be determined independently of the sample matrix, thereby reducing extraction times. Efficiencies close to 100% have been provided by the three modes, which differ in the extraction time required for total removal of the target compounds. The time needed for the dynamic mode was shorter than that for the static mode. However, the establishment of a static extraction step prior to dynamic extraction was the key to shorten the time required for complete extraction. The method has been applied to a certified reference material (CRM 524, BCR, industrial soil/organics) for quality assurance/validation.
Analytical Chemistry 09/2002; 74(16):4213-9. · 5.86 Impact Factor
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ABSTRACT: A microwave-assisted extraction procedure using water as extractant has been performed for the extraction of acid herbicides
(namely, bentazone, 2,4-D, trichlopyr, 2,4,5-T and 2,4,5-Tp) from different types of soil. Two experimental designs were used
for the optimization of the leaching step. The selection of water as extractant provided a clean approach by avoiding the
use of organic solvents. The use of water also enhanced the extraction efficiency due to the high interaction of the microwave
irradiation with polar solvents. The time required for total removal of the target compounds was 35 min. The recoveries yield
were from 87.64 to 106.14% with a repeatability (expressed as relative standard deviation) ranging between 1.34 and 9.24%.
A within-laboratory reproducibility, also expressed as relative standard deviation, varied from 3.97 to 10.41%. A flow-injection
manifold allowed automation of the whole process by hyphenating the steps subsequent to extraction (namely, filtration, preconcentration,
chromatographic separation and UV detection) for the determination of the analytes.
Chromatographia 01/2002; 55(3):117-122. · 1.20 Impact Factor
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ABSTRACT: A dynamic ultrasound-assisted extraction (UAE) method with on-line pre-column derivatization/high performance liquid chromatography (HPLC) and fluorimetric detection is proposed for the analysis of colistin in feed. A flow injection manifold is used for the development of the extraction and derivatization steps and for interfacing them with the separation/detection step, thus providing an on-line approach with the advantage of minimum sample handling. The derivatization was performed with ortho-phthaldialdehyde and 2-mercaptoethanol. The optimum conditions for colistin extraction and formation of the fluorescent derivative have been obtained by experimental design methodology. The use of a high-intensity probe sonication makes UAE an expeditious (7 min versus >1 h) and efficient (93.1–98.2% versus 87.5–94% of recovery) alternative as compared with extraction using an ultrasonic bath. The within-laboratory reproducibility and repeatability, expressed as percentage of relative standard deviation, were 5.2 and 5.8, respectively.
Journal of Chromatography A.
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ABSTRACT: A method for the extraction of compounds with different polarity (namely, triclosan, estrone, 17β-estradiol, diethylstilbestrol, 4-octylphenol, procymidone, permethrin, oxyfluorfen, bisphenol A and 2,8-dibenzodichloro-p-dioxin) from marine sediments has been proposed. The proposed method consists of a sequential superheated fluid extraction with dichloromethane in a dynamic manner and with water in a static–dynamic manner for 50 min. The organic and aqueous extracts are independently collected and treated by evaporation and liquid–liquid extraction, respectively. The working conditions were optimized using multivariate approaches. Triclosan, bisphenol A, oxyfluorfen and permethrin were quantitatively extracted with repeatability and reproducibility in the range 2.9–9.1 and 5.5–9.1% R.S.D., respectively. The analytes were identified and quantified by gas chromatography–tandem mass spectrometry. The method was compared with conventional Soxhlet for the extraction of the analytes from spiked (at low ppb levels) sediments collected at the outflow of an urban wastewater treatment plant and non-spiked sediment collected from a sporting harbour. Statistical differences between the results of both methods were not found from the t-test for 95% of confidence level (p-value = 0.131).
Analytica Chimica Acta.
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ABSTRACT: An automated screening approach for fluoroquinolone (FQ) antibiotics (norfloxacin and ciprofloxacin) in soil samples has been developed. The proposed approach consists on dynamic microwave-assisted extraction and subsequent real-time on-line monitoring of the analytes extracted; thus, the extraction is halted when complete leaching of the analytes has been reached (independently of the sample matrix), avoiding extraction times in excess. The end of the extraction allowed quantifying the total content of the analytes. The extraction was carried out using pure water as extractant and consisted of a number of extraction cycles (depending on the sample matrix) in which the sample was subjected to microwave irradiation while the direction of the extractant was changed in an iterative manner. The target analytes were fluorometrically monitored after derivatization with a terbium (Tb3+)/tri-n-octylphosphine oxide (TOPO)/cetylpyridinium chloride (CPCl)/acetate buffer solution. Optimum conditions for analytes extraction and formation of FQ–Tb3+–TOPO ternary complexes have been obtained using the experimental design methodology. The mean recoveries from soil samples spiked with 5 and 0.5 μg/g of each analyte were (95.2 ± 4.16%) and (98 ± 5.21%), respectively. The within-laboratory reproducibility and repeatability, expressed as relative standard deviation, were 7.29 and 5.80%, respectively. The approach only allows monitoring of the overall content of the species that yield fluorescent complexes with the derivatizing reagent, so the use of chromatography is mandatory for individual separation/quantification of the target compounds.
Journal of Chromatography A.
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ABSTRACT: The growing trend both to avoid the use of organic solvents and reduce the time needed to extract pollutants from environmental solid samples has led to the use of water assisted by auxiliary energies for leaching. The most common of the auxiliary energies used are high pressure–high temperature, microwaves and ultrasounds. One of the most interesting aspects of the use of water in combination with auxiliary energies is the possibility of coupling extraction with other steps of the analytical process, thus enabling partial or total automation of the analytical process, so it is expedited. The addition of reagents (such as surfactants, acids, etc.) to water enlarges its field of application and provides an additional way of shortening the leaching time; thus allowing the establishment of environmental friendly methods. A review about the potential of water as extractant and its main applications so far is here presented.
Analytica Chimica Acta.
