Eduardo Carasek | Universidade Federal de Santa Catarina - UFSC (Federal University of Santa Catarina) (original) (raw)

Papers by Eduardo Carasek

Research paper thumbnail of A proof‐of‐concept of parallel single‐drop microextraction for the rapid and sensitive biomonitoring of pesticides in urine

Journal of Separation Science

Research paper thumbnail of Determination of bisphenol A: Old problem, recent creative solutions based on novel materials

Journal of Separation Science

Research paper thumbnail of Exploring Polypyrrole as Extraction Phase for Disposable Pipette Extraction Method for Multiclass Organic Micro-Pollutant Determination in River and Tap Water Using Gas Chromatography-Mass Spectrometry

Journal of the Brazilian Chemical Society

The use of a polypyrrole (PPy) is described as an efficient extraction phase for disposable pipet... more The use of a polypyrrole (PPy) is described as an efficient extraction phase for disposable pipette extraction (DPX), in a fast and ruggedized analytical method for simultaneous determination of 18 organic micro-pollutants in water using gas chromatography-mass spectrometry (GC-MS). The DPX-blank pipettes were filled with PPy, a material produced through the chemical polymerization of PPy using iron(III) chloride hexahydrate. The optimized conditions were 5 extraction cycles with 600 µL of sample, adjusted to pH 9, and desorption with 150 µL of ethyl acetate using 7 cycles with the same aliquot. The calibration curves resulted in determination coefficient (R 2) higher than 0.9963, the limit of detection (LOD) ranged from 0.4 to 1.5 µg L −1 , and the limit of quantification (LOQ) were from 1.4 to 5.0 µg L −1. Excellent results were obtained for repeatability (2.3 to 15%, for 5 µg L −1) and intermediate precision, varying the day of analyses (3.9 to 15.5%) and the pipette tip (3.4 to 22.4%). The analyte recovery ranged from 75.4 to 115.0% for river water, and from 74.9 to 116.2% for tap water, in three different levels of concentration. The DPX-GC-MS method with PPy was successfully applied to determine the 18 analytes in river and tap water from the cities of Joinville and Florianópolis,

Research paper thumbnail of Expanding the applicability of magnetic ionic liquids for multiclass determination in biological matrices based on dispersive liquid–liquid microextraction and HPLC with diode array detector analysis

Journal of Separation Science

Research paper thumbnail of Returning to Nature for the Design of Sorptive Phases in Solid-Phase Microextraction

Separations

Green analytical chemistry principles aim to minimize the negative impact of analytical procedure... more Green analytical chemistry principles aim to minimize the negative impact of analytical procedures in the environment, which can be considered both at close (to ensure the safety of the analysts) and global (to conserve our natural resources) levels. These principles suggest, among other guidelines, the reduction/minimization of the sample treatment and the use of renewable sources when possible. The first aspect is largely fulfilled by microextraction, which is considered to be among the greenest sample treatment techniques. The second consideration is attainable if natural products are used as raw materials for the preparation of new extraction phases. This strategy is in line with the change in our production system, which is being gradually moved from a linear model (take–make–dispose) to a circular one (including reusing and recycling as key terms). This article reviews the potential of natural products as sorbents in extraction and microextraction techniques from the synergic ...

Research paper thumbnail of Effective and High-Throughput Analytical Methodology for the Determination of Lead and Cadmium in Water Samples by Disposable Pipette Extraction Coupled with High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry (HR-CS GF AAS)

Research paper thumbnail of Alternative Green Extraction Phases Applied to Microextraction Techniques for Organic Compound Determination

Separations

The use of green extraction phases has gained much attention in different fields of study, includ... more The use of green extraction phases has gained much attention in different fields of study, including in sample preparation for the determination of organic compounds by chromatography techniques. Green extraction phases are considered as an alternative to conventional phases due to several advantages such as non-toxicity, biodegradability, low cost and ease of preparation. In addition, the use of greener extraction phases reinforces the environmentally-friendly features of microextraction techniques. Thus, this work presents a review about new materials that have been used in extraction phases applied to liquid and sorbent-based microextractions of organic compounds in different matrices.

Research paper thumbnail of Assessment of a Fully Optimized DPX-Based Procedure for the Multiclass Determination of Pesticides in Drinking Water Using High-Performance Liquid Chromatography with Diode Array Detection

Journal of the Brazilian Chemical Society

In this study, a disposable pipette extraction (DPX)-based procedure was fully optimized for the ... more In this study, a disposable pipette extraction (DPX)-based procedure was fully optimized for the multiclass determination of 12 pesticides, with significant differences in their physicochemical properties, using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD). The variables optimized were type of extraction phase, sample pH, sample volume, number of extraction and desorption cycles, time of each cycle, type and volume of desorption solvent, and NaCl concentration of the samples. The analytical parameters of merit were determined under optimized conditions and satisfactory results were achieved, with limits of detection (LOQs) varying from 0.06 µg L-1 for carbofuran to 2.30 µg L-1 for carbendazim and correlation coefficients of 0.9923 to 0.9999. Relative recoveries ranged from 75 to 117%. Good results were achieved for intraday (n = 3) precision (1 to 20%) and interday (n = 9) precision (1 to 24%). The method was applied to the monitoring of 20 drinking water samples collected from water treatment plants.

Research paper thumbnail of A natural and renewable biosorbent phase as a low-cost approach in disposable pipette extraction technique for the determination of emerging contaminants in lake water samples

Journal of Separation Science

This study proposes an efficient analytical methodology using a biosorbent (cork) as an extractio... more This study proposes an efficient analytical methodology using a biosorbent (cork) as an extraction phase in disposable pipette extraction technique for the rapid determination of the emerging contaminants methyl paraben, ethyl paraben, benzophenone, 3-(4-methylbenzylidene) camphor and 2-(ethylhexyl)-4-(dimethylamino) benzoate in lake water samples using high-performance liquid chromatography with diode array detection. The optimized conditions were comprised of 800 μL of sample, three cycles of 30 s each for the extraction, pH 6, addition of 30% w/v of NaCl. For the desorption step, the optimized desorption conditions were achieved with 100 μL of a mixture comprised of 50% methanol and 50% acetonitrile v/v, using one cycle of 30 s. Excellent analytical performance was achieved with limits of detection of 0.6 μg/L for methyl paraben to 1.4 μg/L for 3-(4-methylbenzylidene) camphor, and the limit of quantitation varied from 2 μg/L for methyl paraben to 4.3 μg/L 3-(4methylbenzylidene) camphor, respectively. The correlation coefficients ranged from 0.9962 for ethyl paraben to 0.9980 for methyl paraben. The method accuracy varied from 71-132%, and the intraday precision ranged from 3 to 23% (n = 3) and interday from 9 to 23% (n = 9). The robustness was evaluated through Youden and Lenth's methods and indicated no significant variations in the results.

Research paper thumbnail of Use of a Natural Sorbent as Alternative Solid-Phase Microextraction Coating for the Determination of Polycyclic Aromatic Hydrocarbons in Water Samples by Gas Chromatography-Mass Spectrometry

Journal of the Brazilian Chemical Society

In this study, the use of bracts as a natural sorbent in solid-phase microextraction was exploite... more In this study, the use of bracts as a natural sorbent in solid-phase microextraction was exploited for use in the determination of polycyclic aromatic hydrocarbons in water samples with separation/detection performed by gas chromatography-mass spectrometry. Fiber-to-fiber reproducibility was evaluated and the relative standard deviation (RSD) was lower than 14%. Optimizations were performed using both the proposed and DVB/Car/PDMS (divinylbenzene/ carboxen/polydimethylsiloxane) fibers. The optimum extraction conditions were 80 min of extraction at 50 °C with 12% (m/v) NaCl for the bract fiber, and 100 min of extraction at 80 °C for the commercial fiber. The limits of detection and quantification for the proposed fiber were, respectively, 0.003 and 0.01 µg L-1 for fluorene, phenanthrene, anthracene and pyrene, and 0.03 and 0.1 µg L-1 for acenaphthylene, benzo(a)anthracene and chrysene. The method using bract fiber provided relative recoveries ranging from 68 to 117%, intraday and interday precisions lower than 17 and 19%, respectively, and extraction efficiency similar to that of the DVB/Car/PDMS fiber.

Research paper thumbnail of Magnetic ionic liquids as versatile extraction phases for the rapid determination of estrogens in human urine by dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography-diode array detection

Analytical and bioanalytical chemistry, 2018

In this study, a rapid and straightforward approach based on magnetic ionic liquids (MIL) as extr... more In this study, a rapid and straightforward approach based on magnetic ionic liquids (MIL) as extraction phases and dispersive liquid-liquid microextraction (DLLME) was developed to analyze the hormones estriol, 17-β-estradiol, 17-α-ethynylestradiol, and estrone in human urine samples. This is the first report of an application of manganese-based MILs compatible with HPLC to extract compounds of biological interest from urine samples. The hydrophobic MILs trihexyltetradecylphosphonium tetrachloromanganate (II) ([P][MnCl]) and aliquat tetrachloromanganate (II) ([Aliquat][MnCl]) were employed and the optimized extraction conditions were comprised of 5 mg of MIL ([P][MnCl]), 5 μL of methanol (MeOH) as disperser solvent, and an extraction time of 90 s at sample pH 6. The analytical parameters of merit were determined under optimized conditions and very satisfactory results were achieved, with LODs of 2 ng mL for all analytes, determination coefficients (R) ranging from 0.9949 for 17-β-es...

Research paper thumbnail of Application of an NiTi alloy coated with ZrO2 solid-phase microextraction fiber for determination of haloanisoles in red wine samples

Mikrochimica Acta, 2009

This study describes an application of ZrO 2 electrolytically deposited onto an NiTi alloy (NiTi-... more This study describes an application of ZrO 2 electrolytically deposited onto an NiTi alloy (NiTi-ZrO 2) as a solid-phase microextraction (SPME) fiber to the determination of 2,4,6-trichloroanisole, 2,4,6-tribromoanisole and pentachloroanisole in red wine samples at the ng L −1 level. Separation and detection was carried out by gas chromatography and electron capture, respectively. The parameters affecting extraction efficiency, such as extraction time and temperature, salting-out effect and sample pH, were simultaneously optimized firstly by means of a two-level full factorial experimental design including a center point, and subsequently through a Doehlert design for three-variables. Excellent robustness, evaluated through a factorial design study, was obtained for all variables considered in the extraction procedure. Detection limits in the range of 6.8 to 8.0 ng L −1 were obtained. Precision was excellent, relative standard deviations being lower than 7.0%. Good accuracy was obtained with calibration against a synthetic solution and 25% dilution of wine samples. The extraction capability of the fiber was stable for more than 700 extractions. Thus, it is an excellent alternative for use in SPME.

Research paper thumbnail of Use of Nb 2O 5–SiO 2 in an automated on-line preconcentration system for determination of copper and cadmium by FAAS

Talanta, 2004

A procedure for the determination of trace level of copper(II) and cadmium(II) by FAAS using an o... more A procedure for the determination of trace level of copper(II) and cadmium(II) by FAAS using an on-line preconcentration system has been proposed. In this system, copper and cadmium ions were adsorbed onto a minicolumn packed with silica gel modified with niobium(V) oxide (Nb 2 O 5-SiO 2), followed by nitric acid elution in reverse mode and determination on-line by flame atomic absorption spectrometry (AAS) without interference of the matrix. Chemical and flow variables as well as concomitant ions were studied in the developed procedure. The enrichment factor for copper(II) and cadmium(II) was 34.2 and 33.0, respectively, using a preconcentration time of 2 min. The limit of detection for copper(II) and cadmium(II) was 0.4, and 0.1 g l −1 , respectively. The precision of the method, evaluated as the relative standard deviation in solutions containing 15 g l −1 of copper and 10 g l −1 of cadmium, by analyzing a series of seven replicates, was 1.8 and 1.6%, respectively. The accuracy was assessed through recovery experiments of certified material and water samples.

Research paper thumbnail of Headspace solid-phase microextraction–gas chromatographic–time-of-flight mass spectrometric methodology for geographical origin verification of coffee

Analytica Chimica Acta, Jun 9, 2008

... b Department of Chemistry, Federal University of Santa Catarina, Trindade, Florianópolis, 880... more ... b Department of Chemistry, Federal University of Santa Catarina, Trindade, Florianópolis, 88040-900, Santa Catarina, Brazil. ... A high-pressure Merlin Microseal septumless injection kit (Merlin Instrument Co., Half Moon Bay, CA, USA) was obtained from Chromatographic ...

Research paper thumbnail of Speciation of Cr(III) and Cr(VI) in environmental samples determined by selective separation and preconcentration on silica gel chemically modified with niobium(V) oxide

Journal of Hazardous Materials, Jan 15, 2009

In this study a new method for chromium speciation in water using solid phase extraction coupled ... more 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.

Research paper thumbnail of A simple sample preparation procedure for the fast screening of selenium species in soil samples using alkaline extraction and hydride-generation graphite furnace atomic absorption spectrometry

Microchemical Journal, 2016

This work presents a simple procedure using alkaline slurry and ultrasonic extraction for the det... more This work presents a simple procedure using alkaline slurry and ultrasonic extraction for the determination of selenium in soil samples by atomic absorption spectrometry with hydride generation and using graphite furnace (HG-GF AAS). The method allows the fractionation of the Se (IV) and Se (VI) species by the subtraction of Se (IV) from Total Se. The extraction has been performed with sodium hydroxide solution (0.5 mol L-1) while the supernatant of the extractions was used for the hydride generation and atomized using a GF coated with iridium as chemical modifier. The temperature program of the GF was optimized and the limits of detection and quantification for the developed method were 6 µg L-1 and 20 µg L-1, respectively, with linear range between 20 to 100 µg L-1 showing a linear coefficient of 0.999. The extraction efficiency was verified comparing the results obtained by the determination of total Se in the supernatant of the proposed method by high-resolution continuum source and graphite furnace atomic absorption spectrometry (HR-CS GF AAS), while the accuracy of the method was available using assisted-microwave digestion and direct solid sampling analysis by HR-CS GF AAS of the certified reference material of soil (MURST-ISS-A1 – Antartic marine sediment) and (BCR 142R – light sandy soil), as well as different soil samples from different regions of Brazil.

Research paper thumbnail of Novel analytical procedure using a combination of hollow fiber supported liquid membrane and dispersive liquid-liquid microextraction for the determination of aflatoxins in soybean juice by high performance liquid chromatography - Fluorescence detector

Food chemistry, 2016

This study describes a combination between hollow fiber membrane and dispersive liquid-liquid mic... more This study describes a combination between hollow fiber membrane and dispersive liquid-liquid microextraction for determination of aflatoxins in soybean juice by HPLC. The main advantage of this approach is the use of non-chlorinated solvent and small amounts of organic solvents. The optimum extraction conditions were 1-octanol as immobilized solvent; toluene and acetone at 1:5 ratio as extraction and disperser solvents (100μL), NaCl at 2% of the sample volume and extraction time of 60min. The optimal condition for the liquid desorption was 150μL acetonitrile:water (50:50 v/v) and desorption time of 20min. The linear range varied from 0.03 to 21μgL(-1), with R(2) coefficients ranging from 0.9940 to 0.9995. The limits of detection and quantification ranged from 0.01μgL(-1) to 0.03μgL(-1) and from 0.03μgL(-1) to 0.1μgL(-1), respectively. Recovery tests ranged from 72% to 117% and accuracy between 12% and 18%.

Research paper thumbnail of The Use of Glass Ceramic as Sufarce to PDMS Coating by Sol Gel Process and its application in SPME FBPOL-2005

Research paper thumbnail of Uso de SPME-CG-EM na identificação dos constituintes voláteis das flores e raízes de Polygala cyparissias

Research paper thumbnail of A liquid-liquid microextraction system for Pb and Cd enrichment and determination by flame atomic absorption spectrometry

Química Nova

A method for determination of lead and cadmium in aqueous samples using solvent microextraction a... more A method for determination of lead and cadmium in aqueous samples using solvent microextraction and dithizone as complexing agent with FAAS was developed. Solvent microextraction parameters were optimized. The effect of foreign ions on the extraction yields was studied. The extraction was carried out until the aqueous to organic phase ratio achieved a 250 fold preconcentration of metals. For preconcentration times of 4 min the 3σ detection limits, relative standard deviations (n=7) and linear calibration ranges were 1.6 μg L -1, 5.8% and 10.0 - 80.0 μg L -1 for lead and 11.1 ng L -1, 5.9% and 0.3 - 3.0 μg L -1 for cadmium, respectively. The solvent microextraction procedure presented here was applied to the determination of lead and cadmium in natural waters.

Research paper thumbnail of A proof‐of‐concept of parallel single‐drop microextraction for the rapid and sensitive biomonitoring of pesticides in urine

Journal of Separation Science

Research paper thumbnail of Determination of bisphenol A: Old problem, recent creative solutions based on novel materials

Journal of Separation Science

Research paper thumbnail of Exploring Polypyrrole as Extraction Phase for Disposable Pipette Extraction Method for Multiclass Organic Micro-Pollutant Determination in River and Tap Water Using Gas Chromatography-Mass Spectrometry

Journal of the Brazilian Chemical Society

The use of a polypyrrole (PPy) is described as an efficient extraction phase for disposable pipet... more The use of a polypyrrole (PPy) is described as an efficient extraction phase for disposable pipette extraction (DPX), in a fast and ruggedized analytical method for simultaneous determination of 18 organic micro-pollutants in water using gas chromatography-mass spectrometry (GC-MS). The DPX-blank pipettes were filled with PPy, a material produced through the chemical polymerization of PPy using iron(III) chloride hexahydrate. The optimized conditions were 5 extraction cycles with 600 µL of sample, adjusted to pH 9, and desorption with 150 µL of ethyl acetate using 7 cycles with the same aliquot. The calibration curves resulted in determination coefficient (R 2) higher than 0.9963, the limit of detection (LOD) ranged from 0.4 to 1.5 µg L −1 , and the limit of quantification (LOQ) were from 1.4 to 5.0 µg L −1. Excellent results were obtained for repeatability (2.3 to 15%, for 5 µg L −1) and intermediate precision, varying the day of analyses (3.9 to 15.5%) and the pipette tip (3.4 to 22.4%). The analyte recovery ranged from 75.4 to 115.0% for river water, and from 74.9 to 116.2% for tap water, in three different levels of concentration. The DPX-GC-MS method with PPy was successfully applied to determine the 18 analytes in river and tap water from the cities of Joinville and Florianópolis,

Research paper thumbnail of Expanding the applicability of magnetic ionic liquids for multiclass determination in biological matrices based on dispersive liquid–liquid microextraction and HPLC with diode array detector analysis

Journal of Separation Science

Research paper thumbnail of Returning to Nature for the Design of Sorptive Phases in Solid-Phase Microextraction

Separations

Green analytical chemistry principles aim to minimize the negative impact of analytical procedure... more Green analytical chemistry principles aim to minimize the negative impact of analytical procedures in the environment, which can be considered both at close (to ensure the safety of the analysts) and global (to conserve our natural resources) levels. These principles suggest, among other guidelines, the reduction/minimization of the sample treatment and the use of renewable sources when possible. The first aspect is largely fulfilled by microextraction, which is considered to be among the greenest sample treatment techniques. The second consideration is attainable if natural products are used as raw materials for the preparation of new extraction phases. This strategy is in line with the change in our production system, which is being gradually moved from a linear model (take–make–dispose) to a circular one (including reusing and recycling as key terms). This article reviews the potential of natural products as sorbents in extraction and microextraction techniques from the synergic ...

Research paper thumbnail of Effective and High-Throughput Analytical Methodology for the Determination of Lead and Cadmium in Water Samples by Disposable Pipette Extraction Coupled with High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry (HR-CS GF AAS)

Research paper thumbnail of Alternative Green Extraction Phases Applied to Microextraction Techniques for Organic Compound Determination

Separations

The use of green extraction phases has gained much attention in different fields of study, includ... more The use of green extraction phases has gained much attention in different fields of study, including in sample preparation for the determination of organic compounds by chromatography techniques. Green extraction phases are considered as an alternative to conventional phases due to several advantages such as non-toxicity, biodegradability, low cost and ease of preparation. In addition, the use of greener extraction phases reinforces the environmentally-friendly features of microextraction techniques. Thus, this work presents a review about new materials that have been used in extraction phases applied to liquid and sorbent-based microextractions of organic compounds in different matrices.

Research paper thumbnail of Assessment of a Fully Optimized DPX-Based Procedure for the Multiclass Determination of Pesticides in Drinking Water Using High-Performance Liquid Chromatography with Diode Array Detection

Journal of the Brazilian Chemical Society

In this study, a disposable pipette extraction (DPX)-based procedure was fully optimized for the ... more In this study, a disposable pipette extraction (DPX)-based procedure was fully optimized for the multiclass determination of 12 pesticides, with significant differences in their physicochemical properties, using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD). The variables optimized were type of extraction phase, sample pH, sample volume, number of extraction and desorption cycles, time of each cycle, type and volume of desorption solvent, and NaCl concentration of the samples. The analytical parameters of merit were determined under optimized conditions and satisfactory results were achieved, with limits of detection (LOQs) varying from 0.06 µg L-1 for carbofuran to 2.30 µg L-1 for carbendazim and correlation coefficients of 0.9923 to 0.9999. Relative recoveries ranged from 75 to 117%. Good results were achieved for intraday (n = 3) precision (1 to 20%) and interday (n = 9) precision (1 to 24%). The method was applied to the monitoring of 20 drinking water samples collected from water treatment plants.

Research paper thumbnail of A natural and renewable biosorbent phase as a low-cost approach in disposable pipette extraction technique for the determination of emerging contaminants in lake water samples

Journal of Separation Science

This study proposes an efficient analytical methodology using a biosorbent (cork) as an extractio... more This study proposes an efficient analytical methodology using a biosorbent (cork) as an extraction phase in disposable pipette extraction technique for the rapid determination of the emerging contaminants methyl paraben, ethyl paraben, benzophenone, 3-(4-methylbenzylidene) camphor and 2-(ethylhexyl)-4-(dimethylamino) benzoate in lake water samples using high-performance liquid chromatography with diode array detection. The optimized conditions were comprised of 800 μL of sample, three cycles of 30 s each for the extraction, pH 6, addition of 30% w/v of NaCl. For the desorption step, the optimized desorption conditions were achieved with 100 μL of a mixture comprised of 50% methanol and 50% acetonitrile v/v, using one cycle of 30 s. Excellent analytical performance was achieved with limits of detection of 0.6 μg/L for methyl paraben to 1.4 μg/L for 3-(4-methylbenzylidene) camphor, and the limit of quantitation varied from 2 μg/L for methyl paraben to 4.3 μg/L 3-(4methylbenzylidene) camphor, respectively. The correlation coefficients ranged from 0.9962 for ethyl paraben to 0.9980 for methyl paraben. The method accuracy varied from 71-132%, and the intraday precision ranged from 3 to 23% (n = 3) and interday from 9 to 23% (n = 9). The robustness was evaluated through Youden and Lenth's methods and indicated no significant variations in the results.

Research paper thumbnail of Use of a Natural Sorbent as Alternative Solid-Phase Microextraction Coating for the Determination of Polycyclic Aromatic Hydrocarbons in Water Samples by Gas Chromatography-Mass Spectrometry

Journal of the Brazilian Chemical Society

In this study, the use of bracts as a natural sorbent in solid-phase microextraction was exploite... more In this study, the use of bracts as a natural sorbent in solid-phase microextraction was exploited for use in the determination of polycyclic aromatic hydrocarbons in water samples with separation/detection performed by gas chromatography-mass spectrometry. Fiber-to-fiber reproducibility was evaluated and the relative standard deviation (RSD) was lower than 14%. Optimizations were performed using both the proposed and DVB/Car/PDMS (divinylbenzene/ carboxen/polydimethylsiloxane) fibers. The optimum extraction conditions were 80 min of extraction at 50 °C with 12% (m/v) NaCl for the bract fiber, and 100 min of extraction at 80 °C for the commercial fiber. The limits of detection and quantification for the proposed fiber were, respectively, 0.003 and 0.01 µg L-1 for fluorene, phenanthrene, anthracene and pyrene, and 0.03 and 0.1 µg L-1 for acenaphthylene, benzo(a)anthracene and chrysene. The method using bract fiber provided relative recoveries ranging from 68 to 117%, intraday and interday precisions lower than 17 and 19%, respectively, and extraction efficiency similar to that of the DVB/Car/PDMS fiber.

Research paper thumbnail of Magnetic ionic liquids as versatile extraction phases for the rapid determination of estrogens in human urine by dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography-diode array detection

Analytical and bioanalytical chemistry, 2018

In this study, a rapid and straightforward approach based on magnetic ionic liquids (MIL) as extr... more In this study, a rapid and straightforward approach based on magnetic ionic liquids (MIL) as extraction phases and dispersive liquid-liquid microextraction (DLLME) was developed to analyze the hormones estriol, 17-β-estradiol, 17-α-ethynylestradiol, and estrone in human urine samples. This is the first report of an application of manganese-based MILs compatible with HPLC to extract compounds of biological interest from urine samples. The hydrophobic MILs trihexyltetradecylphosphonium tetrachloromanganate (II) ([P][MnCl]) and aliquat tetrachloromanganate (II) ([Aliquat][MnCl]) were employed and the optimized extraction conditions were comprised of 5 mg of MIL ([P][MnCl]), 5 μL of methanol (MeOH) as disperser solvent, and an extraction time of 90 s at sample pH 6. The analytical parameters of merit were determined under optimized conditions and very satisfactory results were achieved, with LODs of 2 ng mL for all analytes, determination coefficients (R) ranging from 0.9949 for 17-β-es...

Research paper thumbnail of Application of an NiTi alloy coated with ZrO2 solid-phase microextraction fiber for determination of haloanisoles in red wine samples

Mikrochimica Acta, 2009

This study describes an application of ZrO 2 electrolytically deposited onto an NiTi alloy (NiTi-... more This study describes an application of ZrO 2 electrolytically deposited onto an NiTi alloy (NiTi-ZrO 2) as a solid-phase microextraction (SPME) fiber to the determination of 2,4,6-trichloroanisole, 2,4,6-tribromoanisole and pentachloroanisole in red wine samples at the ng L −1 level. Separation and detection was carried out by gas chromatography and electron capture, respectively. The parameters affecting extraction efficiency, such as extraction time and temperature, salting-out effect and sample pH, were simultaneously optimized firstly by means of a two-level full factorial experimental design including a center point, and subsequently through a Doehlert design for three-variables. Excellent robustness, evaluated through a factorial design study, was obtained for all variables considered in the extraction procedure. Detection limits in the range of 6.8 to 8.0 ng L −1 were obtained. Precision was excellent, relative standard deviations being lower than 7.0%. Good accuracy was obtained with calibration against a synthetic solution and 25% dilution of wine samples. The extraction capability of the fiber was stable for more than 700 extractions. Thus, it is an excellent alternative for use in SPME.

Research paper thumbnail of Use of Nb 2O 5–SiO 2 in an automated on-line preconcentration system for determination of copper and cadmium by FAAS

Talanta, 2004

A procedure for the determination of trace level of copper(II) and cadmium(II) by FAAS using an o... more A procedure for the determination of trace level of copper(II) and cadmium(II) by FAAS using an on-line preconcentration system has been proposed. In this system, copper and cadmium ions were adsorbed onto a minicolumn packed with silica gel modified with niobium(V) oxide (Nb 2 O 5-SiO 2), followed by nitric acid elution in reverse mode and determination on-line by flame atomic absorption spectrometry (AAS) without interference of the matrix. Chemical and flow variables as well as concomitant ions were studied in the developed procedure. The enrichment factor for copper(II) and cadmium(II) was 34.2 and 33.0, respectively, using a preconcentration time of 2 min. The limit of detection for copper(II) and cadmium(II) was 0.4, and 0.1 g l −1 , respectively. The precision of the method, evaluated as the relative standard deviation in solutions containing 15 g l −1 of copper and 10 g l −1 of cadmium, by analyzing a series of seven replicates, was 1.8 and 1.6%, respectively. The accuracy was assessed through recovery experiments of certified material and water samples.

Research paper thumbnail of Headspace solid-phase microextraction–gas chromatographic–time-of-flight mass spectrometric methodology for geographical origin verification of coffee

Analytica Chimica Acta, Jun 9, 2008

... b Department of Chemistry, Federal University of Santa Catarina, Trindade, Florianópolis, 880... more ... b Department of Chemistry, Federal University of Santa Catarina, Trindade, Florianópolis, 88040-900, Santa Catarina, Brazil. ... A high-pressure Merlin Microseal septumless injection kit (Merlin Instrument Co., Half Moon Bay, CA, USA) was obtained from Chromatographic ...

Research paper thumbnail of Speciation of Cr(III) and Cr(VI) in environmental samples determined by selective separation and preconcentration on silica gel chemically modified with niobium(V) oxide

Journal of Hazardous Materials, Jan 15, 2009

In this study a new method for chromium speciation in water using solid phase extraction coupled ... more 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.

Research paper thumbnail of A simple sample preparation procedure for the fast screening of selenium species in soil samples using alkaline extraction and hydride-generation graphite furnace atomic absorption spectrometry

Microchemical Journal, 2016

This work presents a simple procedure using alkaline slurry and ultrasonic extraction for the det... more This work presents a simple procedure using alkaline slurry and ultrasonic extraction for the determination of selenium in soil samples by atomic absorption spectrometry with hydride generation and using graphite furnace (HG-GF AAS). The method allows the fractionation of the Se (IV) and Se (VI) species by the subtraction of Se (IV) from Total Se. The extraction has been performed with sodium hydroxide solution (0.5 mol L-1) while the supernatant of the extractions was used for the hydride generation and atomized using a GF coated with iridium as chemical modifier. The temperature program of the GF was optimized and the limits of detection and quantification for the developed method were 6 µg L-1 and 20 µg L-1, respectively, with linear range between 20 to 100 µg L-1 showing a linear coefficient of 0.999. The extraction efficiency was verified comparing the results obtained by the determination of total Se in the supernatant of the proposed method by high-resolution continuum source and graphite furnace atomic absorption spectrometry (HR-CS GF AAS), while the accuracy of the method was available using assisted-microwave digestion and direct solid sampling analysis by HR-CS GF AAS of the certified reference material of soil (MURST-ISS-A1 – Antartic marine sediment) and (BCR 142R – light sandy soil), as well as different soil samples from different regions of Brazil.

Research paper thumbnail of Novel analytical procedure using a combination of hollow fiber supported liquid membrane and dispersive liquid-liquid microextraction for the determination of aflatoxins in soybean juice by high performance liquid chromatography - Fluorescence detector

Food chemistry, 2016

This study describes a combination between hollow fiber membrane and dispersive liquid-liquid mic... more This study describes a combination between hollow fiber membrane and dispersive liquid-liquid microextraction for determination of aflatoxins in soybean juice by HPLC. The main advantage of this approach is the use of non-chlorinated solvent and small amounts of organic solvents. The optimum extraction conditions were 1-octanol as immobilized solvent; toluene and acetone at 1:5 ratio as extraction and disperser solvents (100μL), NaCl at 2% of the sample volume and extraction time of 60min. The optimal condition for the liquid desorption was 150μL acetonitrile:water (50:50 v/v) and desorption time of 20min. The linear range varied from 0.03 to 21μgL(-1), with R(2) coefficients ranging from 0.9940 to 0.9995. The limits of detection and quantification ranged from 0.01μgL(-1) to 0.03μgL(-1) and from 0.03μgL(-1) to 0.1μgL(-1), respectively. Recovery tests ranged from 72% to 117% and accuracy between 12% and 18%.

Research paper thumbnail of The Use of Glass Ceramic as Sufarce to PDMS Coating by Sol Gel Process and its application in SPME FBPOL-2005

Research paper thumbnail of Uso de SPME-CG-EM na identificação dos constituintes voláteis das flores e raízes de Polygala cyparissias

Research paper thumbnail of A liquid-liquid microextraction system for Pb and Cd enrichment and determination by flame atomic absorption spectrometry

Química Nova

A method for determination of lead and cadmium in aqueous samples using solvent microextraction a... more A method for determination of lead and cadmium in aqueous samples using solvent microextraction and dithizone as complexing agent with FAAS was developed. Solvent microextraction parameters were optimized. The effect of foreign ions on the extraction yields was studied. The extraction was carried out until the aqueous to organic phase ratio achieved a 250 fold preconcentration of metals. For preconcentration times of 4 min the 3σ detection limits, relative standard deviations (n=7) and linear calibration ranges were 1.6 μg L -1, 5.8% and 10.0 - 80.0 μg L -1 for lead and 11.1 ng L -1, 5.9% and 0.3 - 3.0 μg L -1 for cadmium, respectively. The solvent microextraction procedure presented here was applied to the determination of lead and cadmium in natural waters.