Low-cost approach to increase the analysis throughput of bar adsorptive microextraction (BAµE) combined with environmentally-friendly renewable sorbent phase of recycled diatomaceous earth.

In this study, a novel apparatus for bar adsorptive microextraction (BAµE) using a voltage regulator was proposed as an alternative tool to improve the analysis throughput. In addition, recycled diatomaceous earth obtained as a brewery residue was employed as a biosorbent coating for the determination of methyl paraben, ethyl paraben, benzophenone and triclocarban in water samples by high-performance liquid chromatography-diode array detection (HPLC-DAD). The use of the extraction devices, comprised of floating adsorptive bars of 7.5mm length, in the extractions with magnetic stirrers linked to a voltage regulator enabled the analysis of multiple samples, simultaneously. The method optimization was carried out by univariate and multivariate analyses. The optimal conditions for the method were sample solution at pH 5, extraction time of 90min and liquid desorption in 100µL of acetonitrile:methanol (50:50, v/v) for 15min. The total sample preparation time was 17.5min per sample for a simultaneous batch of six extractions. The R2 values for the calibration curves obtained were higher than 0.9985. The limits of detection (LODs) varied from 0.19 to 2µgL-1 and the limits of quantification (LOQs) ranged from 0.63 to 6.9µgL-1. The method was applied to freshwater samples collected from Peri Lagoon (Florianópolis, SC, Brazil) and the relative recoveries ranged from 63% to 124% with relative standard deviations (RSDs) of < 20% (n = 2). The RSD values for the reproducibility of the performance of the magnetic stirrers and inter-device extraction efficiency were lower than 14% (n = 3) and 11% (n = 3), respectively.

Novel approach to high-throughput determination of endocrine disruptors using recycled diatomaceous earth as a green sorbent phase for thin-film solid-phase microextraction combined with 96-well plate system.

A sustainable approach to TF-SPME is presented using recycled diatomaceous earth, obtained from a beer purification process, as a green sorbent phase for the determination of bisphenol A (BPA), benzophenone (BzP), triclocarban (TCC), 4-methylbenzylidene camphor (4-MBC) and 2-ethylhexyl-p-methoxycinnamate (EHMC) in environmental water samples. TF-SPME was combined with a 96-well plate system allowing for high-throughput analysis due to the simultaneous extraction/desorption up to 96 samples. The proposed sorbent phase exhibited good stability in organic solvents, as well as satisfactory analytical performance. The optimized method consisted of 240 min of extraction at pH 6 with the addition of NaCl (15% w/v). A mixture of MeOH:ACN (50:50 v/v) was used for the desorption the analytes, using a time of 30 min. Limits of detection varied from 1 µg L-1 for BzP and TCC to 8 µg L-1 for the other analytes, and R2 ranged from 0.9926 for 4-MBC to 0.9988 for BPA. This novel and straightforward approach offers an environmentally-friendly and very promising alternative for routine analysis. . The total sample preparation time per sample was approximately 2.8 min, which is a significant advantage when a large number of analytical run is required.

A low-cost biosorbent-based coating for the highly sensitive determination of organochlorine pesticides by solid-phase microextraction and gas chromatography-electron capture detection.

In this study, an environmentally friendly and low-cost biosorbent coating was evaluated, for the first time, as the extraction phase for solid-phase microextraction (SPME) supported on a nitinol alloy. The characterization of the new fiber was performed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The applicability of the biosorbent-based fiber in the determination of δ-hexachlorocyclohexane, aldrin, heptachlor epoxide, α-endosulfan, endrin and 4,4'-DDD in water samples was verified, with separation/detection by gas chromatography coupled to electron capture detection (GC-ECD). The influencing parameters (temperature, extraction time and ionic strength) were optimized simultaneously using a central composite design. The optimum conditions were: extraction time of 80min at 80°C and sodium chloride concentration of 15% (w/v). Satisfactory analytical performance was achieved with limits of detection (LOD) between 0.19 and 0.71ngL-1 and limits of quantification (LOQ) between 0.65 and 2.38ngL-1. The relative recoveries for the analytes were determined using river and lake water samples spiked at different concentrations and ranged from 60% for α-endosulfan to 113% for δ-hexachlorocyclohexane, with relative standard deviations (RSD) lower than 21%. The fiber-to-fiber reproducibility (n=3) was also evaluated and the RSD was lower than 14%. The extraction efficiency obtained for the proposed biosorbent coating was compared to a commercially available DVB/Car/PDMS coating. The proposed fiber provided very promising results, including LODs at the level of parts per trillion and highly satisfactory thermal and mechanical stability.

Determination of phthalates and adipate in physiological saline solutions by solid-phase microextraction and gas chromatography.

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.

Application of robust NiTi-ZrO2-PEG SPME fiber in the determination of haloanisoles in cork stopper samples.

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.

Application of poly(dimethylsiloxane) fiber sol-gel coated onto NiTi alloy electrodeposited with zirconium oxide for the determination of organochlorine pesticides in herbal infusions.

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.

New poly(ethylene glycol) solid-phase microextraction fiber employing zirconium oxide electrolytically deposited onto a NiTi alloy as substrate for sol-gel reactions.

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.

A combination of statistical and analytical evaluation methods as a new optimization strategy for the quantification of pharmaceutical residues in sewage effluent.

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.

Preparation and characterization of new solid-phase microextraction fibers obtained by sol-gel technology and zirconium oxide electrodeposited on NiTi alloy.

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.

Application of NiTi alloy coated with ZrO2 as a new fiber for solid-phase microextraction for determination of halophenols in water samples.

A new fiber for solid-phase microextraction (SPME) employing a metallic support coated with an inorganic material is proposed. A nitinol alloy (NiTi) was used as the support material due to its super elasticity and shape memory properties. Zirconium oxide (ZrO2) was electrodeposited onto NiTi using chronoamperometry. The surface characteristics and morphology of the coated and uncoated support were evaluated through scanning electronic microscopy and dispersive energy microanalysis. This assembly was applied in the extraction of three halophenols from aqueous samples. A multivariate approach was used for optimization of the variables involved in the system. The Doehlert matrix was used for evaluation of the best derivatization conditions and a Box-Behnken design to obtain the best extraction conditions. In order to investigate the repeatability, one fiber was used for six extraction tests under similar conditions and the relative standard deviations (R.S.D.) were lower than 12.5%. Detection limits were lower than 0.30 ng mL(-1). Correlation coefficients were higher than 0.997. Extraction efficiency of the NiTi-ZrO2 fiber was similar to a PDMS 7 microm commercial fiber, even though it had a lower coating thickness of 1.35 microm. Considering the amount extracted per unit volume, the NiTi-ZrO2 fiber had a better extraction profile when compared to commercial fibers. The new SPME fiber has a lifetime of over 500 extractions. Thus, it is a promising alternative for low-cost analysis, as the proposed fiber is robust, and easily and inexpensively prepared.

Preparation and application of NiTi alloy coated with ZrO(2) as a new fiber for solid-phase microextraction.

In this study a NiTi alloy was applied as an SPME support due to its superelasticity and shape memory properties. This new metallic support was coated with ZrO(2) by electrodeposition using chronoamperometry. It was then evaluated for extraction of three classes of compounds from gaseous samples: alcohols, BTEX and trihalomethanes (THM). For the optimization of the parameters affecting the extraction efficiency of the target compounds, the univariate approach was used. Five fibers were electrodeposited to evaluate the reproducibility of the coating procedure, resulting in a relative standard deviation lower than 11.9%. The repeatability for one fiber (n=6) was lower than 8.5%. The detection limits were lower than 28.1, 20.8 and 0.18 microgL(-1) for alcohols, BTEX and THM, respectively, and the correlation coefficients were higher than 0.996. Taking into account the amount extracted per unit volume, the NiTi-ZrO(2) fiber showed a better extraction profile in comparison with the commercial fibers 7 microm PDMS, 85 microm PA and 30-50 microm DVB/CAR/PDMS. The new SPME fiber has a lifetime of over 300 extractions. Thus, it is a promising alternative for low-cost analysis, as it is robust, and easily and inexpensively prepared.

Application of fractional factorial experimental and Box-Behnken designs for optimization of single-drop microextraction of 2,4,6-trichloroanisole and 2,4,6-tribromoanisole from wine samples.

In this paper a new method for the determination of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA) in wine samples is presented. Headspace single-drop microextraction (HS-SDME) was used for the extraction and preconcentration of the analytes, followed by analysis by gas chromatography and electron-capture detection (GC-ECD). The variables affecting extraction efficiency were optimized using fractional factorial experimental and Box-Behnken designs. The external calibration procedure was successfully carried out using a synthetic wine solution and diluted red wine samples. The method was also applied to white wine samples. Excellent detection limits of 8.1 and 6.1 ng L(-1) were achieved for TCA and TBA, respectively. Good precision and accuracy were obtained.

Monitoring the formation of trihalomethanes in the effluents from a shrimp hatchery.

Formation of trihalomethanes (THM) was monitored at the Laboratório de Camarões Marinhos (LCM) from the Universidade Federal de Santa Catarina. THM could be present because chlorinated effluents from disinfection are discharged from the different hatchery rooms. THM quantification was done through an analytical methodology using Purge&Trap coupled with a gas chromatograph equipped with an electron capture detector. Relative standard deviation (RSD), limit of detection (LOD) and limit of quantification (LOQ) for the methodology corresponded to the ranges of 8-17%; 0.01-0.03 microg L(-1) and 0.03-0.08 microg L(-1), respectively. Linear working range was of 0.1-8.0 microg L(-1) for all compounds. Enrichment and recovery method was applied to evaluate possible matrix effects and the results varied from 71.2% to 107.9%. LCM was monitored between August and December, 2004. This study showed that THM did not increase with the increase in postlarvae production and also that the aquatic life and the surrounding environment were not affected.