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The catalytic properties of three copper complexes, [Cu(en)2](ClO4)2 (1), [Cu(amp)2](ClO4)2, (2) and [Cu(bpy)2](ClO4)2 (3) (where en = ethylenediamine, amp = 2-aminomethylpyridine and bpy = 2,2'-bipyridine), were explored upon the oxidation of benzyl alcohol (BnOH). Maximized conversions of the substrates to their respective products were obtained using a multivariate analysis approach, a powerful tool that allowed multiple variables to be optimized simultaneously, thus creating a more economical, fast and effective technique. Considering the studies in a fluid solution (homogeneous), all complexes strongly depended on the amount of the oxidizing agent (H2O2), followed by the catalyst load. In contrast, time seemed to be statistically less relevant for complexes 1 and 3 and not relevant for 2. All complexes showed high selectivity in their optimized conditions, and only benzaldehyde (BA) was obtained as a viable product. Quantitatively, the catalytic activity observed was 3 > 2 > 1, which is related to the π-acceptor character of the ligands employed in the study. Density functional theory (DFT) studies could corroborate this feature by correlating the geometric index for square pyramid Cu(II)-OOH species, which should be generated in the solution during the catalytic process. Complex 3 was successfully immobilized in silica-coated magnetic nanoparticles (Fe3O4@SiO2), and its oxidative activity was evaluated through heterogenous catalysis assays. Substrate conversion promoted by 3-Fe3O4@SiO2 generated only BA as a viable product, and the supported catalyst's recyclability was proven. Reduced catalytic conversions in the presence of the radical scavenger (2,2,6,6-tetrametil-piperidi-1-nil)oxil (TEMPO) indicate that radical and non-radical mechanisms are involved.

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The present work describes the development of a headspace solid-phase microextraction (HS-SPME) followed by gas chromatography - mass spectrometry (GC-MS) method for the qualitative analysis of compounds in seized ecstasy tablets that can be easily implemented in regular laboratories. HS-SPME with a DVB/CAR/PDMS 50/30 µm fiber was used to extract the ecstasy pills' components, including major and minor ones, in a single extraction/chromatographic run. For HS-SPME, the incubation time (0 min to 30 min), the extraction time (10 min to 40 min) and temperature (40 °C to 80 ºC), the buffer volume (3 mL to 8 mL), the buffer pH (6 to 9) and the NaCl concentration (0 mol/L to 6 mol/L) were evaluated using fractional factorial design. Different split ratios and detector voltages were also evaluated. The optimal compromise between sensitivity and peak resolution was found to be incubation and extraction at 65 ºC for 10 min and 25 min, respectively, 3 mL of pH 9 buffer containing 3 mol/L NaCl, using 40.0 mg of the powdered samples in a 15-mL amber glass vial, and an injection with a split ratio of 1:10 at 260 ºC for 10 min. Under optimal conditions, 44 samples from different seizures were analyzed. Seventy-five compounds were tentatively identified by the proposed method, including active substances, medicines, caffeine, safrole derivatives, synthesis intermediates and solvent residues. The number of tentatively identified compounds per sample varied from 8 to 24, with a mean of 15. Important findings in ecstasy samples, such as norcinamolaurin, α-methyl-1,3-benzodioxole-5-propanamide, α-methyl-3,4-methylenedioxyphenylpropionitrile, acetylsalicylic acid, piperonylonitrile, methyl isobutyl ketone, mesitylene, and 4-[3-(dimethylamino)propyl]- 2,6-dimethylphenol, identified with a frequency higher than 10%, are not found in the literature so far. The method precision, based on relative standard deviation of peak areas, ranged from 5% to 15%, depending on the compound. The method was shown to be simple, relatively fast, precise and a powerful tool for the identification of major and minor components in ecstasy tablets in a single analytical cycle, being useful for screening or quantitative purposes, if authentic standards are available.

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Inspired by copper-containing enzymes such as galactose oxidase and catechol oxidase, in which distinct coordination environments and nuclearities lead to specific catalytic activities, we summarize here the catalytic properties of dinuclear and mononuclear copper species towards benzyl alcohol oxidation using a multivariate statistical approach. The new dinuclear [Cu2(µ-L1)(µ-pz)]2+ (1) is compared against the mononuclear [CuL2Cl] (2), where (L1)- and (L2)- are the respective deprotonated forms of 2,6-bis((bis(pyridin-2-ylmethyl)amino)methyl)-4-methylphenol, and 3-((bis(pyridin-2-ylmethyl)amino)methyl)-2-hydroxy-5-methylbenzaldehyde and (pz)- is a pyrazolato bridge. Copper(II) perchlorate (CP) is used as control. The catalytic oxidation of benzyl alcohol is pursued, aiming to assess the role of the ligand environment and nuclearity. The multivariate statistical approach allows for the search of optimal catalytic conditions, considering variables such as catalyst load, hydrogen peroxide load, and time. Species 1, 2 and CP promoted selective production of benzaldehyde at different yields, with only negligible amounts of benzoic acid. Under normalized conditions, 2 showed superior catalytic activity. This species is 3.5-fold more active than the monometallic control CP, and points out to the need for an efficient ligand framework. Species 2 is 6-fold more active than the dinuclear 1, and indicates the favored nuclearity for the conversion of alcohols into aldehydes.

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This paper proposes a new optimization strategy for the extraction of volatile compounds from honey samples using headspace solid-phase microextraction (HS-SPME) and separation/detection by gas chromatography-mass spectrometry (GC-MS). The new optimization strategy was based on the use of three different extraction temperatures in a single assay, aiming at extracting a high number of compounds with wide range of volatilities. As an analytical tool, experimental designs were used for the optimization. The variables extraction time (10-80 min), extraction temperature (0-60 °C), water volume (0.5-5 mL) and percentage of sodium chloride saturation in water (0-100%) were optimised using a five-level fractional central composite design with CAR/DVB/PDMS fibre. The final optimised combination of extraction times at each temperature was 60 min with the sample temperature being held at 60 °C for 36 min, 40 °C for 18 min and 0 °C for 6 min. The proposed method was compared to conventional methods which employ one or two extraction temperatures. It was found that the proposed method presented better results considering the response in terms of the arithmetic means of the peak areas. The use of multiple extraction temperatures for the HS-SPME procedure proved to be an excellent alternative for the screening of compounds present in honey with a wide range of volatilities.

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This study proposes a new optimization approach for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and xylene isomers (BTEX) from water samples using the solid-phase microextraction technique followed by gas chromatography-mass spectrometry (GC-MS) separation and detection. The objective of the study was to achieve compromise extraction conditions, suitable for all semi-volatile and volatile compounds, under which the amount extracted is maximized for all analytes. This was achieved by careful optimization of the fiber coating, salting-out effect, extraction time and temperature and extraction mode (headspace or direct immersion). With the optimized fiber coating - PDMS/DVB 65 µm - the other selected factors were optimized using a response surface methodology through central composite designs. As expected, the optimized results for each class of analytes varied significantly, probably due to the differences in their volatility and the equilibrium constants for the analyte/fiber coating. In order to overcome this issue, a new optimization approach was proposed based on a combination of extraction modes and extraction temperatures in a single extraction procedure. The final optimized procedure was: 48 min of extraction in direct immersion mode with the sample maintained at 80 °C followed by a further 32 min of headspace extraction with the sample temperature kept at 10 °C. The proposed procedure was compared with conventional methods based on the use of a single extraction mode and temperature (80 min of headspace extraction at 60 °C or 80 min of direct immersion extraction at 50 °C). The newly proposed method was shown to be more attractive as it extracted higher amounts of both semi-volatile and volatile compounds in a single extraction procedure compared to the conventional approaches. The optimized method was validated and excellent results were obtained.

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This paper proposes a new analytical procedure based on the headspace solid-phase microextraction (HS-SPME) technique and gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) for the determination of 16 phenols extracted from leather samples. The optimized conditions for the HS-SPME were obtained through two experimental designs - a two-level fractional factorial design followed by a central composite design - using the commercial SPME fiber polyacrylate 85 µm (PA). The best extraction conditions were as follows: 200 µL of derivatizing agent (acetic anhydride), 20 mL of saturated aqueous NaCl solution and extraction time and temperature of 50 min and 75°C, respectively. All optimized conditions were obtained with fixed leather sample mass (250 mg), vial volume (40 mL) and phosphate buffer pH (12) and concentration (50 mmol/L). Detection limits ranging from 0.03 to 0.20 ng/g, and relative standard deviation (RSD) lower than 10.23% (n=6) for a concentration of 800 ng/g (chlorophenols) and 1325 ng/g (2-phenylphenol) in the splitless mode were obtained. The recovery was studied at three concentration levels by adding different amounts of phenols to the leather sample and excellent recoveries ranging from 90.0 to 107.2% were obtained. The validated method was shown to be suitable for the quantification of phenols in leather samples, as it is simple, relatively fast and sensitive.

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A new method for Ag determination in water samples using solid phase extraction (SPE) coupled to a flow injection system and flame atomic absorption spectrometry was developed. The sorbent used for Ag preconcentration and extraction was the termite digestion product. Flow and chemical variables of the system were optimized through a multivariate procedure. The factors selected were adsorbent mass, buffer type and concentration, sample pH, and sample flow rate. The detection limit and precision were 3.4 µg L(-1) and 3.8% (n = 6, 15 µg L(-1)), respectively. The enrichment factor and the linear working range were, respectively, 21 and 10-50 µg L(-1). Results for recovery tests using different water samples were between 96 and 107%. The proposed methodology was applied with success for the determination of Ag in water used to wash clothes impregnated with silver nanoparticles, supplied by a factory located in Santa Catarina, Brazil.

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This study proposes a new approach to the optimization of the extraction of the volatile fraction of plant matrices using the headspace solid-phase microextraction (HS-SPME) technique. The optimization focused on the extraction time and temperature using a CAR/DVB/PDMS 50/30 µm SPME fiber and 100mg of a mixture of plants as the sample in a 15-mL vial. The extraction time (10-60 min) and temperature (5-60 °C) were optimized by means of a central composite design. The chromatogram was divided into four groups of peaks based on the elution temperature to provide a better understanding of the influence of the extraction parameters on the extraction efficiency considering compounds with different volatilities/polarities. In view of the different optimum extraction time and temperature conditions obtained for each group, a new approach based on the use of two extraction temperatures in the same procedure is proposed. The optimum conditions were achieved by extracting for 30 min with a sample temperature of 60 °C followed by a further 15 min at 5 °C. The proposed method was compared with the optimized conventional method based on a single extraction temperature (45 min of extraction at 50 °C) by submitting five samples to both procedures. The proposed method led to better results in all cases, considering as the response both peak area and the number of identified peaks. The newly proposed optimization approach provided an excellent alternative procedure to extract analytes with quite different volatilities in the same procedure.

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This study describes a new approach to cold-fiber solid-phase microextraction (CF-SPME) based on a combination of different extraction modes in the same extraction procedure. Also, the high quantity of water required to facilitate both the desorption of analytes from the matrix and their transport to the fiber coating is reported. The extraction mode was changed from the direct to the headspace mode in a single extraction while manipulating the extraction times and coating temperature to improve the extraction of compounds with different volatilities. Compounds with low volatility were better extracted in the direct mode, while the headspace mode was more appropriate for volatile compounds. Polycyclic aromatic hydrocarbons (PAHs) and phthalic acid esters (PEs) in sand or soil samples were used as model compounds and matrices in this study. The optimized conditions were: sample pH in the range of 4-7, addition of 12 mL of 194 g L(-1) aqueous NaCl solution in a 15 mL vial, and 80 min total extraction time with a sample temperature of 90°C (50 min in direct mode with coating at 90°C followed by 30 min in headspace mode with coating at 30°C). The proposed procedure was compared with conventional CF-SPME (with and without addition of water) and was found to be more effective for all the analytes, since it is capable of extracting both heavier and lighter compounds from soil samples in a single extraction procedure. The use of an excess of water and a combination of extraction modes in the same CF-SPME procedure are the main factors responsible for this enhancement. The proposed method was applied to the extraction of PAHs and PEs in spiked soil samples and excellent results were obtained for most of the compounds evaluated.

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This study describes a new optimization strategy for internally cooled solid-phase microextraction based on a multivariate approach. The coating temperature was changed in an extraction while manipulating the extraction times to improve the extraction of compounds with different volatilities. Polycyclic aromatic hydrocarbons (PAHs) and phthalic acid esters (PEs) and adipate were used as model compounds in this study. The optimization strategy was in two steps: (1) multivariate optimization of extraction time and initial coating temperature and (2) multivariate optimization of total extraction time and the time required to cool the coating to a lower temperature as determined in step 1. The observed analytical response in relation to the coating temperature was found to be dependent on the analyte volatility and size. The optimized extraction condition for PEs was 23 min extraction while maintaining the coating at 140°C, followed by 7 min of cooling the coating at 10°C. For the PAHs the coating temperature was maintained at 60°C for the first 20 min and at 5°C in the last 20 min of extraction. Comparisons have been made between the proposed optimized conditions with the conventional internally cooled fiber approach and the results thoroughly discussed. The proposed optimization strategy was found to be more effective for all the analytes, especially for the semi-volatiles, compared to the conventional method.

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In this study a new method for determination of cadmium in alcohol fuel using Moringa oleifera seeds as a biosorbent in an on-line preconcentration system coupled to flame atomic absorption spectrometry (FAAS) was developed. Flow and chemical variables of the proposed system were optimized through multivariate designs. The limit of detection for cadmium was 5.50microg L(-1) and the precision was below 2.3% (35.0microg L(-1), n=9). The analytical curve was linear from 5 to 150microg L(-1), with a correlation coefficient of 0.9993. The developed method was successfully applied to spiked alcohol fuel, and accuracy was assessed through recovery tests, with recovery ranging from 97.50 to 100%.

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This review outlines recent progress in the research on some new classes of sorbents for extraction and microextraction techniques. Carbon nanotubes are allotropes of carbon with cylindrical structure. They are very stable systems having considerable chemical inertness due to the strong covalent bonds of the carbon atoms on the nanotube surface. Some applications of carbon nanotubes are presented in a perspective view. Molecular imprinting has proved to be an effective technique for the creation of recognition sites on a polymer scaffold. By a mechanism of molecular recognition, the molecularly imprinted polymers are used as selective tools for the development of various analytical techniques such as liquid chromatography, capillary electrochromatography, solid-phase extraction (SPE), binding assays and biosensors. Sol-gel chemistry provides a convenient pathway to create advanced material systems that can be effectively utilized to solve the solid phase microextraction fiber technology problems. This review is mainly focused on recent advanced developments in the design, synthesis and application of sol-gel in preparation of coatings for the SPME fibers.

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This study describes an analytical methodology developed for determination of phthalate esters (di-n-butyl, butylbenzyl and di-2-ethylhexyl phthalate) and adipate (di-n-ethylhexyl adipate) by solid-phase microextraction (SPME) and gas chromatography in normal saline solutions and, in bi-distilled water used to reconstitute medicines. An 85-microm-polyacrylate SPME fiber was selected and used in all analyses. The parameters affecting extraction efficiency were simultaneously optimized, firstly by means of a two-level full factorial design including a center point and subsequently through a Doehlert design for two-variables. Satisfactory detection limits in the range of 0.18 to 0.75 microg L(-1) and excellent precision, with relative standard deviation values being lower than 15.1% (n = 6), were obtained. Relative sensitivities of between 72.3 and 124.3% were obtained.

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In this study a method for the determination of cadmium in fuel alcohol using solid-phase extraction with a flow injection analysis system and detection by flame atomic absorption spectrometry was developed. The sorbent material used was a vermicompost commonly used as a garden fertilizer. The chemical and flow variables of the on-line preconcentration system were optimized by means of a full factorial design. The selected factors were: sorbent mass, sample pH, buffer concentration and sample flow rate. The optimum extraction conditions were obtained using sample pH in the range of 7.3-8.3 buffered with tris(hydroxymethyl)aminomethane at 50 mmol L(-1), a sample flow rate of 4.5 mL min(-1) and 160 mg of sorbent mass. With the optimized conditions, the preconcentration factor, limit of detection and sample throughput were estimated as 32 (for preconcentration of 10 mL sample), 1.7 microg L(-1) and 20 samples per hour, respectively. The analytical curve was linear from 5 up to at least 50 microg L(-1), with a correlation coefficient of 0.998 and a relative standard deviation of 2.4% (35 microg L(-1), n=7). The developed method was successfully applied to spiked fuel alcohol, and accuracy was assessed through recovery tests, with recovery ranging from 94% to 100%.

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In this study a new method for chromium speciation in water using solid phase extraction coupled to a flow injection system and flame atomic absorption spectrometry was developed. The adsorption behavior of Cr(III) and Cr(VI) on Nb2O5-SiO2 allowed the selective separation of Cr(III) from Cr(VI) in the pH range of 6-9. Thus, a method for Cr(III) preconcentration and extraction using Nb2O5-SiO2 was developed. Total chromium was determined after the reduction of Cr(VI) to Cr(III) using sodium sulfite in acidic medium. The operational variables of the preconcentration and reduction procedures were optimized through full factorial and Doehlert designs. The limit of detection for Cr(III) was 0.34microgL(-1) and the precision was below 4.6%. Results for recovery tests using different environmental samples were between 90 and 105%. Certified reference materials (NIST 1640 and NIST 1643e) were analyzed in order to check the accuracy of the proposed method, and the results were in agreement with the certified values.

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In this study, a novel solid-phase microextraction (SPME) fiber obtained using sol-gel technology was applied in the determination of off-flavor compounds (2,4,6-trichloroanisole (TCA), 2,4,6-tribromoanisole (TBA) and pentachloroanisole (PCA)) present in cork stopper samples. A NiTi alloy previously electrodeposited with zirconium oxide was used as the substrate for a poly(ethylene glycol) (PEG) coating. Scanning electronic microscopy showed good uniformity of the coating and allowed the coating thickness to be estimated as around 17 micarom. The optimization of the main parameters influencing the extraction efficiency, such as cork sample mass, sodium chloride mass, extraction temperature and extraction time were optimized using a full factorial design, followed by a Doehlert design. The optimum conditions were: 20 min of extraction at 70 degrees C using 60 mg of the cork sample and 10 mL of water saturated with sodium chloride in a 20 mL amber vial with constant magnetic stirring. Satisfactory detection limits between 2.5 and 5.1 ng g(-1) were obtained, as well as good precision (R.S.D. in the range of 5.8-12.0%). Recovery tests were performed on three different cork samples, and values between 83 and 119% were obtained. The proposed SPME fiber was compared with commercially available fibers and good results were achieved, demonstrating its applicability.

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A PDMS fiber sol-gel coated onto an NiTi alloy previously electrodeposited with zirconium oxide (named NiTi-ZrO(2)-PDMS) was applied to the determination of organochlorine pesticides (OCPs) in infusions of peppermint (Mentha piperita L.), lemon grass (Cymbopogon citratus Stapf), chamomile (Matricaria recutita L.), lemon balm (Melissa officinalis L.), and anise seeds (Pimpinella anisum L.). Salting-out effect, extraction time, and extraction temperature were optimized firstly by means of a full-factorial design and then using a Doehlert matrix. No salt addition and 50 min of extraction at 70 degrees C were the optimum conditions. Satisfactory LODs in the range of 2-17 ng/L, as well as good correlation coefficients (at least 0.9981) in the linear range studied, were obtained. Calibration was successfully applied using an infusion of M. recutita L. and recovery tests were performed to ensure the accuracy of the method, with values in the range of 77-120%. Comparison of the NiTi-ZrO(2)-PDMS with commercially available PDMS fibers showed that the proposed fiber has an extraction efficiency comparable to that of PDMS 30 microm for the compounds evaluated, demonstrating its potential applicability.

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In this study zirconium oxide electrolytically deposited onto a NiTi alloy (NiTi-ZrO(2)) was employed as a new substrate for sol-gel reactions for the fabrication of an efficient and unbreakable solid-phase microextraction fiber. The NiTi-ZrO(2) surface was activated and used as a substrate for coating with poly(ethylene glycol) sol solution. Fibers produced with and without a ZrO(2) layer were compared and, through scanning electron micrographs, an excellent attachment of the polymer in the case of the NiTi-ZrO(2) substrate was demonstrated. The proposed fiber showed excellent thermal stability up to the maximum temperature evaluated of 320 degrees C, suggesting a strong interaction between the substrate surface and the polymeric coating, probably due to chemical bonding. The applicability of the proposed fiber was evaluated through extraction of halophenols and phthalate esters from the headspace and directly from aqueous sample, respectively. Some parameters affecting the extraction efficiency were optimized by full-factorial and Doehlert experimental designs, and the analytical features were estimated. Detection limits in the range of 1.2-9.8 ng L(-1) for halophenols and 0.3-0.7 microg L(-1) for phthalate esters were obtained. Repeatability for one fiber (n=6) was in the range of 4.6-10.6% and fiber-to-fiber reproducibility (n=5) was lower than 12% for all compounds. The results suggest that the proposed fiber can be successfully applied for the determination of these compounds in water and also can be extended to other analytes and matrices.

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In this study, a new solid-phase microextraction (SPME) method for simultaneous extraction of pharmaceutical compounds with acidic and basic characteristics (ibuprofen, fenoprofen, diclofenac, diazepam and loratadine) from residual water samples is proposed. In this procedure, the extraction is processed using two distinct sample pH values. The extraction is begun at pH 2.5 to promote the sorption of acidic pharmaceuticals and after 35 min the sample pH is changed to 7.0 by adding 0.4 mol L(-1) disodium hydrogenphosphate, so that the basic compounds can be sorbed by the fiber (20 min). The pH change is performed without interruption of the extraction process. A comparison between the proposed method and the SPME method applied to each group of the target compounds was performed. Gas chromatography coupled to mass spectrometry was used for separation and detection of analytes. The extraction conditions for the three methods were optimized using full factorial experimental design, response surface through a Doehlert matrix and central composite design. Limits of detection (0.02-0.43 microg L(-1)) and correlation coefficients (0.9970-0.9998) were determined for the three methods. The proposed extraction procedure was applied to samples of sewage treatment plant effluent and untreated wastewater. Recovery and relative standard deviation values ranged from 67 to 116% and 4.6 to 14.5%, respectively, for all compounds studied. Modification of sample pH during the extraction procedure was shown to be an excellent option for all of the compounds and may be extended to the simultaneous extraction of other compounds with different acid-base characteristics.

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This study describes the use of zirconium oxide electrolytically deposited onto a NiTi alloy as a new substrate for sol-gel reactions. Polydimethylsiloxane (PDMS) was used to coat the fiber after activation of the NiTi-ZrO(2) surface with sodium hydroxide solution followed by hydrochloric acid solution. Micrographs obtained by scanning electron microscopy (SEM) showed good uniformity of the PDMS coating on the proposed substrate and also permitted the evaluation of coating thickness, being approximately 25 microm. Thermal stability of the coating on the NiTi-ZrO(2) surface was evaluated, showing excellent stability up to 320 degrees C. The applicability of the proposed NiTi-ZrO(2)-PDMS fiber was evaluated through extraction of benzene, toluene, ethylbenzene and o-xylene (BTEX) from the headspace of aqueous samples. Some parameters affecting the extraction efficiency such as the salting-out effect, extraction temperature and extraction time were optimized by two consecutive two-level full-factorial experimental designs. This optimization allowed the experimental domain of maximum response to be attained and also the robustness range for the variables. Excellent detection limits in the range of 0.6-1.6 microg L(-1) were obtained as well as correlation coefficients higher than 0.99994. Precision for one fiber (n=7) was in the range of 1.4-4.0% and fiber-to-fiber reproducibility (n=5) was in the range of 3.9-6.7%. Comparison of the extraction profile of the proposed fiber with those of commercially available 100, 30 and 7 microm PDMS fibers showed that NiTi-ZrO(2)-PDMS had a better response compared to that of the 7 and 30 microm fibers. Such characteristics of the NiTi-ZrO(2)-PDMS fiber suggest that this fiber represents an excellent alternative for gas chromatography sample preparation.

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