RESUMO

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-(4-methylbenzylidene) 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.

Assuntos

RESUMO

This paper describes a new configuration of the hollow fiber renewal liquid membrane (HFRLM) procedure for the high-throughput determination of the endocrine disrupting compounds 4-nonylphenol, 4-octylphenol, 4-tert-octylphenol, methylparaben, ethylparaben and bisphenol A using a 96-well plate system and high-performance liquid chromatography. In this configuration, cylindrical blades were adapted as a support for polypropylene membranes used as supported liquid membranes in the HFRLM approach. The proposed configuration exhibited important advantages including high-throughput, low solvent and sample consumption, and good analytical performance. The optimized extraction conditions were achieved with the use of a mixture comprised of 50:50 v/v 1-octanol:hexane as the supported liquid membrane, sample pH 5, extraction solvent 15 µL (hexane) and extraction time 45 min. The limits of quantification varied from 0.5 µg L-1 for 4-octylphenol to 15 µg L-1 for methylparaben and ethylparaben and the r2 ranged from 0.9908 for methylparaben to 0.9992 for 4-tert-octylphenol. HFRLM combined with the use of a 96-well plate provides an environmentally-friendly configuration. It offers good accuracy when applied to analyze water samples, with relative recoveries ranging from 72 to 130%, for 4-octylphenol and 4-nonylphenol, respectively, and precision varying from 1 to 14.3%, for 4-nonylphenol at 1.0 µg L-1 and bisphenol A at 8.0 µg L-1, respectively.

RESUMO

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.

RESUMO

In this study, a new method was developed in which a biosorbent material is used as the extractor phase in conjunction with a recently described sample preparation technique called thin-film microextraction and a 96-well plate system. The method was applied for the determination of emerging contaminants, such as 3-(4-methylbenzylidene) camphor, ethylparaben, triclocarban, and bisphenol A in water samples. The separation and detection of the analytes were performed by high-performance liquid chromatography with diode array detection. These contaminants are considered hazardous to human health and other living beings. Thus, the development of an analytical method to determine these compounds is of great interest. The extraction parameters were evaluated using multivariate and univariate optimization techniques. The optimum conditions for the method were 3 h of extraction time, 20 min of desorption with 300 µL of acetonitrile and methanol (50:50, v/v), and the addition of 5% w/v sodium chloride to the sample. The analytical figures of merit showed good results with linear correlation coefficients higher than 0.99, relative recoveries of 72-125%, interday precision (n = 3) of 4-18%, and intraday precision (n = 9) of 1-21%. The limit of detection was 0.3-5.5 µg/L, and the limit of quantification was 0.8-15 µg/L.

RESUMO

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.

Assuntos

RESUMO

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.

Assuntos

RESUMO

In this paper, a remodeling of the bar adsorptive microextraction (BAµE) technique is proposed with impregnation of the derivatization reagent on the surface of the adsorptive bar containing a biosorbent material. The derivatization reagent was 2,4-dinitrophenylhydrazine (DNPH), which was adsorbed on the surface of the bar containing cork powder as the extractor phase for the determination of two aldehydes (hexanal and heptanal) which are known as lung cancer biomarkers in human urine samples. The derivatization reaction and the extraction occurred simultaneously on the surface of the bar (length 7.5 mm) under acidic conditions. The method optimization was carried out by univariate and multivariate analysis. The optimal conditions for the method were a DNPH to aldehydes ratio of 40:1, buffer solution of pH 4.0, extraction time of 60 min and liquid desorption of 10 min in 100 µL of acetonitrile. The aldehydes were analyzed by HPLC-DAD with a simple and fast (6 min) chromatographic run. The limits of detection (LODs) for hexanal and heptanal were 1.00 and 0.73 µmol L-1, respectively. The relative recoveries in urine samples ranged from 88 to 111% with relative standard deviations (RSDs) being less than 7%. The method developed is of low cost and can be successfully used for the quantification of these two lung cancer biomarkers in human urine samples, potentially providing an early diagnosis of lung cancer.

Assuntos

RESUMO

This study describes the use of cork as a new coating for bar adsorptive microextraction (BAµE) and its application in determining benzophenone, triclocarban and parabens in aqueous samples by HPLC-DAD. In this study bars with 7.5 and 15 mm of length were used. The extraction and liquid desorption steps for BAµE were optimized employing multivariate and univariate procedures. The desorption time and solvent used for liquid desorption were optimized by univariate and multivariate studies, respectively. For the extraction step the sample pH was optimized by univariate experiments while the parameters extraction time and ionic strength were evaluated using the Doehlert design. The optimum extraction conditions were sample pH 5.5, NaCl concentration 25% and extraction time 90 min. Liquid desorption was carried out for 30 min with 250 µL (bar length of 15 mm) or 100 µL (bar length of 7.5 mm) of ACN:MeOH (50:50, v/v). The quantification limits varied between 1.6 and 20 µg L(-1) (bar length of 15 mm) and 0.64 and 8 µg L(-1) (bar length of 7.5 mm). The linear correlation coefficients were higher than 0.98 for both bars. The method with 7.5 mm bar length showed recovery values between 65 and 123%. The bar-to-bar reproducibility and the repeatability were lower than 13% (n = 2) and 14% (n = 3), respectively.

Assuntos

RESUMO

The simultaneous use of a hollow-fiber-supported liquid membrane and dispersive liquid-liquid microextraction for the determination of pesticides directly in grape juice was investigated. The detection and quantification were performed by liquid chromatography with diode array detection. The optimum extraction condition was reached by filling the pores of the membrane wall with dodecanol and using hexane/acetone as extraction/dispersion solvents. Salt addition had a highly negative effect on the extraction efficiency and the optimum extraction time was 60 min. The volume of hexane/acetone mixture and the sample pH did not affect the signal at the levels studied. Therefore, an intermediate amount of these solvents (250 µL; 1:7.5 v/v) and pH 6 were selected. The optimum desorption condition was obtained with acetonitrile and 10 min of desorption time. The linear working range varied from 58 to 500 µg/L (parathion-methyl), 62-500 µg/L (difenoconazole) and 107-500 µg/L (chlorpyrifos), with correlation coefficients ranging from 0.9980-0.9942. The limits of detection and quantification found were, respectively, 17 and 58 µg/L for parathion-methyl, 19 and 62 µg/L for difenoconazole and 32 and 107 µg/L for chlorpyrifos. The relative standard deviation ranged between 3.5 and 11.2%.

Assuntos

RESUMO

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.

Assuntos