New procedure for the control of the treatment of industrial effluents to remove volatile organosulfur compounds

We present a new procedure for the determination of volatile organosulfur compounds in samples of industrial effluents using dispersive liquid–liquid microextraction and gas chromatography with flame photometric detection. Initially, the extraction parameters were optimized. These included: type and volume of extraction solvent, volume of disperser solvent, salting out effect, pH, time and speed of centrifugation as well as extraction time. The procedure was validated for 30 compounds. The developed procedure has low detection limits of 0.0071–0.49 μg/L and a good precision (relative standard deviation values of 1.2–5.0 and 0.6–4.1% at concentrations of 1 and 10 μg/L, respectively). The procedure was used to determine the content of volatile organosulfur compounds in samples of effluents from the production of bitumens before and after chemical treatment, in which six compounds were identified, including 2‐mercaptoethanol, thiophenol, thioanisole, dipropyl disulfide, 1‐decanethiol, and phenyl isothiocyanate at concentrations ranging from 0.47 to 8.89 μg/L. Problems in the determination of organosulfur compounds related to considerable changes in composition of the effluents, increase in concentration of individual compounds and appearance of secondary pollutants during effluent treatment processes are also discussed.     

Application of mesoporous carbon as a solid‐phase microextraction fiber coating for the extraction of volatile aromatic compounds

A mesoporous carbon was fabricated using MCM‐41 as a template and sucrose as a carbon source. The carbon material was coated on stainless‐steel wires by using the sol–gel technique. The prepared solid‐phase microextraction fiber was used for the extraction of five volatile aromatic compounds (chlorobenzene, ethylbenzene, o‐xylene, bromobenzene, and 4‐chlorotoluene) from tea beverage samples (red tea and green tea) prior to gas chromatography with mass spectrometric detection. The main experimental parameters affecting the extraction of the volatile aromatic compounds by the fiber, including the extraction time, sample volume, extraction temperature, salt addition, and desorption conditions, were investigated. The linearity was observed in the range from 0.1 to 10.0 μg/L with the correlation coefficients (r) ranging from 0.9923 to 0.9982 and the limits of detection were less than 10.0 ng/L. The recoveries of the volatile aromatic compounds by the method from tea beverage samples at spiking levels of 1.0 and 10.0 μg/L ranged from 73.1 to 99.1%.     

Development of a new stir bar sorptive extraction method for the determination of medium‐level volatile thiols in wine

A fast, simple, and reliable analytical method for the determination of medium‐level volatile thiols in wines is presented. Stir bar sorptive extraction using ethylene glycol‐silicone coated stir bars has been used in combination with thermal desorption gas chromatography with mass spectrometry for the analysis of 4‐mercapto‐4‐methylpentan‐2‐one, 2‐furanmethanethiol, 3‐mercaptohexyl acetate, and 3‐mercaptohexanol in wine. Optimization of the extraction technique was performed using a two‐level fractional factorial design. For the extraction step, the optimum conditions were: Ethylene glycol and silicone coated stir bars, pH at 3.5, sample volume of 25 mL, extraction time of 90 min, NaCl content 4.0 g, and stirring speed at 500 rpm. The optimized method achieved good linearity for all studied compounds (r² > 0.995) and it provided detection limits of 21.52, 0.36, 0.73, and 2.55 μg/L for 4‐mercapto‐4‐methylpentan‐2‐one, 2‐furanmethanethiol, 3‐mercaptohexyl acetate, and 3‐mercaptohexanol, respectively. It was repeatable, with precisions lower than 18% relative standard deviation for both intraday and interday repeatability. The developed procedure is suitable for the determination of these kinds of compounds when they are present at medium concentration levels. It was finally applied to real wine samples with negative aroma derived from the high concentration levels of these compounds.     

PDMS extraction bars for the determination of volatile aromatic hydrocarbons in water and wastewater

In this study, the preparation and application of extraction bars of PDMS were investigated to preconcentrate and determine benzene, toluene, ethylbenzene, and xylene in water and wastewater by means of HPLC with fluorescence detection. Aliquot samples from hospital wastewater were used as the model effluent. The independent variables for the sorptive extraction were as follows: ionic strength (added amounts of NaCl); pH; temperature and time of absorption; temperature and time of desorption. Under optimized conditions, by using a factorial design, the suspended extraction bars could allow the determination of benzene, toluene, ethylbenzene, and xylene (1.20 ± 0.05 μg/L; 10.40 ± 0.02 μg/L; 1.80 ± 0.04 μg/L; 15.9 ± 0.04 μg/L, respectively) in hospital effluent (fortified samples), by recoveries of 71.9 ± 4.9 to 74.8 ± 5.6%. This procedure represents an innovation that eliminates the time‐consuming stage of vacuum microfiltration, and allows the determination of volatile organic compounds by HPLC. As far as we know, this procedure is original and represents an important contribution to the field.     

Polypyrrole‐coated alginate/magnetite nanoparticles composite sorbent for the extraction of endocrine‐disrupting compounds

Magnetite nanoparticles incorporated into alginate beads and coated with a polypyrrole adsorbent were prepared (polypyrrole/Fe₃O₄/alginate bead) and used as an effective magnetic solid‐phase extraction sorbent for the extraction and enrichment of endocrine‐disrupting compounds (estriol, β‐estradiol and bisphenol A) in water samples. The determination of the extracted endocrine‐disrupting compounds was performed using high‐performance liquid chromatography with a fluorescence detector. The effect of various parameters on the extraction efficiency of endocrine disrupting compounds were investigated and optimized including the type and amount of sorbent, sample pH, extraction time, stirring speed, and desorption conditions. Under optimum conditions, the calibration curves were linear in the concentration range of 0.5–100.0 μg/L, and the limit of detection was 0.5 μg/L. The developed method showed a high extraction efficiency, the recoveries were in the range of 90.5 ± 4.1 to 98.2 ± 5.5%. The developed sorbent was easy to prepare, was cost‐effective, robust, and provided a good reproducibility (RSDs < 5%), and could be reused 16 times. The developed method was successfully applied for the determination of endocrine‐disrupting compounds in water samples.     

Low‐temperature headspace‐trap gas chromatography with mass spectrometry for the determination of trace volatile compounds from the fruit of Lycium barbarum L.

The total saccharides content of Lycium barbarum L. is very high, and a high temperature would result in saccharide decomposition and the emergence of a large amount of water. Moreover, the volatile compounds from the fruit of L. barbarum L. are rather low in concentration. Hence, it is difficult for a conventional headspace method to study the volatile compounds from the fruit of L. barbarum L. Since headspace‐trap gas chromatography with mass spectrometry is an excellent method for trace analysis, a headspace‐trap gas chromatography with mass spectrometry method based on low‐temperature (30°C) enrichment and multiple headspace extraction was developed to explore the volatile compounds from the fruit of L. barbarum L. The headspace of the sample was extracted in 17 cycles at 30°C. Each time, the compounds extracted were concentrated in the trap (Tenax TA and Tenax GR, 1:1). Finally, all the volatile compounds were delivered into the gas chromatograph after thermal desorption. With the method described above, a total of 57 compounds were identified. The identification was completed by mass spectral search, retention index, and accurate mass measurement.     

Optimisation of stir bar sorptive extraction applied to the determination of volatile compounds in vinegars

Stir bar sorptive extraction (SBSE) was evaluated for analysing volatile compounds in vinegar. The extraction and desorption analytical conditions have been optimised using a two-level factorial design expanded further to a central composite design. This chemometric tool is very appropriate in screening experiments where the aim is to investigate several possibly influential and/or interacting factors. For the extraction step, the optimum analytical conditions were: sample volume 25 ml without dilution, sampling time 120 min, NaCl content 5.85 g, and stirring speed 1250 rpm. For the desorption step, the optimised analytical conditions were: desorption temperature 300 degrees C, cryofocusing temperature -140 degrees C, flow of helium 75 ml min(-1), and desorption time 10 min. The SBSE procedure developed shows detection limits, and linear ranges adequate for analysing this type of compounds. The repeatability values obtained were lower than 10%. SBSE is a very simple, solvent-free, fast technique with better sensitivities, in general, than SPME. However, a disadvantage of this technique is that, up to now, the stir bar offers a limited enrichment capability for polar compounds because is only available with PDMS coating.     

Use of volatile organic solvents in headspace liquid‐phase microextraction by direct cooling of the organic drop using a simple cooling capsule

A low‐cost and simple cooling‐assisted headspace liquid‐phase microextraction device for the extraction and determination of 2,6,6‐trimethyl‐1,3 cyclohexadiene‐1‐carboxaldehyde (safranal) in Saffron samples, using volatile organic solvents, was fabricated and evaluated. The main part of the cooling‐assisted headspace liquid‐phase microextraction system was a cooling capsule, with a Teflon microcup to hold the extracting organic solvent, which is able to directly cool down the extraction phase while the sample matrix is simultaneously heated. Different experimental factors such as type of organic extraction solvent, sample temperature, extraction solvent temperature, and extraction time were optimized. The optimal conditions were obtained as: extraction solvent, methanol (10 μL); extraction temperature, 60°C; extraction solvent temperature, 0°C; and extraction time, 20 min. Good linearity of the calibration curve (R² = 0.995) was obtained in the concentration range of 0.01–50.0 μg/mL. The limit of detection was 0.001 μg/mL. The relative standard deviation for 1.0 μg/mL of safranal was 10.7% (n = 6). The proposed cooling‐assisted headspace liquid‐phase microextraction device was coupled (off‐line) to high‐performance liquid chromatography and used for the determination of safranal in Saffron samples. Reasonable agreement was observed between the results of the cooling‐assisted headspace liquid‐phase microextraction high‐performance liquid chromatography method and those obtained by a validated ultrasound‐assisted solvent extraction procedure.     

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

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.     

Use of two different coating temperatures for a cold fiber headspace solid‐phase microextraction system to determine the volatile profile of Brazilian medicinal herbs

In this study, the experimental extraction conditions on applying headspace solid‐phase microextraction and cold fiber headspace solid‐phase microextraction (CF‐HS‐SPME) procedures to samples of six medicinal herbs commonly found in southern Brazil were optimized. The optimized conditions for headspace solid‐phase microextraction were found to be an extraction temperature of 60°C and extraction time of 40 min. For CF‐HS‐SPME, the corresponding values were 60°C and 15 min. In the case of the coating temperature for the CF‐HS‐SPME system, two approaches were investigated: (i) Temperature of 5°C applied during the whole extraction procedure; and (ii) the use of two fiber temperatures in the same extraction procedure with the aim of extracting the volatile and semivolatile compounds, the ideal condition being 60°C for the first 7.5 min and 5°C for the final 7.5 min. The three extraction procedures were compared. The CF‐HS‐SPME procedure had good performance only for the more volatile compounds whereas the strategy using two coating temperatures in the same procedure showed good performance for all compounds studied. It was also possible to determine the profile for the volatile fraction of each herb studied applying this technique followed by GC‐MS.     

Multivariate optimization of headspace‐GC for the determination of monoaromatic compounds (benzene,toluene, ethylbenzene,and xylenes) in waters and wastewaters

The objective of this study was to optimize, by employing a central composite rotatable design, and validate an analytical method to detect and quantify monoaromatic compounds (benzene, toluene, ethylbenzene, and xylenes) in waters and wastewaters by using headspace extraction followed by GC coupled with photoionization detection. The extraction parameters optimized were: salinity, sample volume, incubation time, and extraction temperature. The results revealed that the sample volume was the most significant parameter in the extraction process, whereas the salinity effect was negligible, which extends the applicability of the analytical method to waters with different salinities. Finally, the studied method was very selective and, at the optimal extraction conditions (15 mL sample volume, 15 min incubation time, and temperature of 70°C), presented excellent repeatability (<4%), linearity (R > 0.999 for each compound), and sensitivity, since very low LODs (0.13–0.48 μg/L) and LOQs (0.43–1.61 μg/L) were achieved.     

A rapid MCM‐41 dispersive micro‐solid phase extraction coupled with LC/MS/MS for quantification of ketoconazole and voriconazole in biological fluids

A rapid dispersive micro‐solid phase extraction (D‐μ‐SPE) combined with LC/MS/MS method was developed and validated for the determination of ketoconazole and voriconazole in human urine and plasma samples. Synthesized mesoporous silica MCM‐41 was used as sorbent in d ‐μ‐SPE of the azole compounds from biological fluids. Important D‐μ‐SPE parameters, namely type desorption solvent, extraction time, sample pH, salt addition, desorption time, amount of sorbent and sample volume were optimized. Liquid chromatographic separations were carried out on a Zorbax SB‐C₁₈ column (2.1 × 100 mm, 3.5 μm), using a mobile phase of acetonitrile–0.05% formic acid in 5 mm ammonium acetate buffer (70:30, v /v). A triple quadrupole mass spectrometer with positive ionization mode was used for the determination of target analytes. Under the optimized conditions, the calibration curves showed good linearity in the range of 0.1–10,000 μg/L with satisfactory limit of detection (≤0.06 μg/L) and limit of quantitation (≤0.3 μg/L). The proposed method also showed acceptable intra‐ and inter‐day precisions for ketoconazole and voriconazole from urine and human plasma with RSD ≤16.5% and good relative recoveries in the range 84.3–114.8%. The MCM‐41‐D‐μ‐SPE method proved to be rapid and simple and requires a small volume of organic solvent (200 μL); thus it is advantageous for routine drug analysis.     

Simultaneous determination of trace level riot control agents in environmental water by solid-phase microextraction and gas chromatography coupled with a flame ionization detector

In this paper, a direct immersion solid-phase microextraction procedure for the simultaneous analyses of four primary riot control agents: 2-chloroacetophenone, o-chlorobenzylidene malonitrile, dibenz(b,f)-1,4-oxazepine, and oleoresin capsicum at μg/L concentration from environmental water was developed. Several parameters that influence the extraction effectiveness were investigated, including fiber type, extraction temperature, extraction time, starring rate, and salinity. Under the recommended conditions, the optimized method had reasonable linearity and accuracy. The average recovery of this method ranged from 84 to 108.1%. The limit of detection for all the analytes ranged from 0.2 to 3 μg/L and the limit of quantification ranged from 1 to 10 μg/L, respectively. A relative standard deviation from 3.0 to 4.3% can be achieved depending on the compounds. The procedure was applied to analyze all the four riot control agents simultaneously in several environmental samples.     

Solid‐Phase Microextraction Followed by High‐Performance Liquid Chromatography with Fluorimetric and UV Detection for the Determination of Polycyclic Aromatic Hydrocarbons in Water

Abstract

We have developed a solid‐phase microextraction procedure for polycyclic aromatic hydrocarbons. A simplex experimental design was employed to optimize the process. A polydimethylsiloxane/divinylbenzene fiber was selected. The optimum conditions were: an extraction step in the immersion mode, over a period of 60 min at 70°C using high‐speed stirring, and an 8 min desorption step using acetonitrile (90 µl). Linear relationships were obtained for all compounds, except for naphthalene. Our method showed a good precision and accuracy with a detection limit between 0.005 and 0.306 µg l^?1. Our method was used to detect PAHs in real water samples.     

Solid‐phase microextraction Arrow for the volatile organic compounds in soy sauce

A novel solid‐phase microextraction Arrow was used to separate volatile organic compounds from soy sauce, and the results were verified by using gas chromatography with mass spectrometry. Solid‐phase microextraction Arrow was optimized in terms of three extraction conditions: type of fiber used (polydimethylsiloxane, polyacrylate, carbon wide range/polydimethylsiloxane, and divinylbenzene/polydimethylsiloxane), extraction temperature (40, 50, and 60°C), and extraction time (10, 30, and 60 min). The optimal solid‐phase microextraction Arrow conditions were as follows: type of fiber = polyacrylate, extraction time = 60 min, and extraction temperature = 50°C. Under the optimized conditions, the solid‐phase microextraction Arrow was compared with conventional solid‐phase microextraction to determine extraction yields. The solid‐phase microextraction Arrow yielded 6–42‐fold higher levels than in solid‐phase microextraction for all 21 volatile organic compounds detected in soy sauce due to the larger sorption phase volume. The findings of this study can provide practical guidelines for solid‐phase microextraction Arrow applications in food matrixes by providing analytical methods for volatile organic compounds.     

Characterization of volatile substances in apples from Rosaceae family by headspace solid‐phase microextraction followed by GC‐qMS

The volatile composition of different apple varieties of Malus domestica Borkh. species from different geographic regions at Madeira Islands, namely Ponta do Pargo (PP), Porto Santo (PS), and Santo da Serra (SS) was established by headspace solid‐phase microextraction (HS‐SPME) procedure followed by GC‐MS (GC‐qMS) analysis. Significant parameters affecting sorption process such as fiber coating, extraction temperature, extraction time, sample amount, dilution factor, ionic strength, and desorption time, were optimized and discussed. The SPME fiber coated with 50/30 μm divinylbenzene/carboxen/PDMS (DVB/CAR/PDMS) afforded highest extraction efficiency of volatile compounds, providing the best sensitivity for the target volatiles, particularly when the samples were extracted at 50°C for 30 min with constant magnetic stirring. A qualitative and semi‐quantitative analysis between the investigated apple species has been established. It was possible to identify about 100 of volatile compounds among pulp (46, 45, and 39), peel (64, 60, and 64), and entire fruit (65, 43, and 50) in PP, PS, and SS apples, respectively. Ethyl esters, terpenes, and higher alcohols were found to be the most representative volatiles. α‐Farnesene, hexan‐1‐ol and hexyl 2‐methylbutyrate were the compounds found in the volatile profile of studied apples with the largest GC area, representing, on average, 24.71, 14.06, and 10.80% of the total volatile fraction from PP, PS, and SS apples. In PP entire apple, the most abundant compounds identified were α‐farnesene (30.49%), the unknown compound m/z (69, 101, 157) (21.82%) and hexyl acetate (6.57%). Regarding PS entire apple the major compounds were α‐farnesene (16.87%), estragole (15.43%), hexan‐1‐ol (10.94), and E‐2‐hexenal (10.67). α‐Farnesene (30.3%), hexan‐1‐ol (18.90%), 2‐methylbutanoic acid (4.7%), and pentan‐1‐ol (4.6%) were also found as SS entire apple volatiles present in a higher relative content. Principal component analysis (PCA) of the results clustered the apples into three groups according to geographic origin. Linear discriminant analysis (LDA) was performed in order to detect the volatile compounds able to differentiate the three kinds of apples investigated. The most important contributions to the differentiation of the PP, PS, and SS apples were ethyl hexanoate, hexyl 2‐methylbutyrate, E,E‐2,4‐heptadienal, p‐ethyl styrene, and E‐2‐hexenal.     

Sol–gel‐adsorbent‐coated extraction needles to detect volatile compounds in spoiled fish

Volatile compounds generated by fish spoilage were investigated by an inside‐needle microextraction method followed by gas chromatography with flame ionization detection and gas chromatography with mass spectrometry. The inside of a needle was coated with an adsorbent to extract the target analytes from the headspace of the sample. The examined adsorbents included β‐cyclodextrin, polystyrene resin cross‐linked with 1% divinylbenzene, and polyethylene glycol mixed with polydimethylsiloxane. The investigated volatile compounds generated by fish spoilage were acetone, 2‐butanone, 2‐butanol, 2‐propanol, dimethyl disulfide, acetic acid, and benzaldehyde. The analysis conditions for the sorption and desorption processes were optimized. Each optimized condition was validated by determining the limit of detection and the limit of quantitation from the calibration curves, as well as the recovery, reproducibility, and concentration factors. As a result, all of the fabricated needles afforded successful recoveries, above 90%, with relative standard deviations below 10%. In particular, cyclodextrin and polystyrene resin cross‐linked with 1% divinylbenzene mixed with polydimethylsiloxane show good sensitivities and concentration factors for the standard volatile compounds. The storage of fresh mackerel and salted mackerel at room temperature for 14 days caused the concentrations of dimethyl disulfide and acetic acid to significantly increase while those of acetone, 2‐butanone, 2‐propanol, and 2‐butanol changed only slightly.     

New SPME fibre for analysis of mequinol emitted from DVDs

A piece of fused-silica fibre coated with silica modified with ketamine-groups was used as a solidphase microextraction (SPME) fibre and its efficiency in the qualitative and quantitative analysis of volatile organic compounds released from coloured overprinting on DVDs was evaluated. The effect of the parameters that can affect the SPME procedure, such as extraction time, extraction temperature, desorption temperature, was investigated to determine the analytical performance of this novel fibre in the qualitative and quantitative analyses of organic compounds. The optimised procedure was applied to the qualitative and quantitative analyses of organic compounds released from coloured overprinting on DVDs. The limit of detection of 4-methoxyphenol (mequinol) was 88 × 10⁻³ μg mL⁻¹, while the limit of quantification (LOQ) was calculated as ten times the baseline noise, i.e. 3.1 × 10⁻¹ μg mL⁻¹. The proposed fibre was used successfully for preconcentration of the volatile organic compounds from the gaseous phase of DVD samples.     

New procedure for the examination of the degradation of volatile organonitrogen compounds during the treatment of industrial effluents

We present a new procedure for the determination of 32 volatile organonitrogen compounds in samples of industrial effluents with a complex matrix. The procedure, based on dispersive liquid–liquid microextraction followed by gas chromatography with nitrogen‐phosphorus and mass spectrometric detection, was optimized and validated. Optimization of the extraction included the type of extraction and disperser solvent, disperser solvent volume, pH, salting out effect, extraction, and centrifugation time. The procedure based on nitrogen‐phosphorus detection was found to be superior, having lower limits of detection (0.0067–2.29 μg/mL) and quantitation as well as a wider linear range. The developed procedure was applied to the determination of content of volatile organonitrogen compounds in samples of raw effluents from the production of bitumens in which 13 compounds were identified at concentrations ranging from 0.15 to 10.86 μg/mL and in samples of effluents treated by various chemical methods.     

Preparation and application of a coated‐fiber needle extraction device

In this study, a needle‐trap device with fibers coated with a molecularly imprinted polymer was developed for separation. A number of heat‐resistant Zylon filaments were longitudinally packed into a glass capillary, followed by coating with a molecularly imprinted polymer. Then, the molecularly imprinted polymer coating was copolymerized and anchored onto the surface of the fibers. The bundle of synthetic fibers coated with the molecularly imprinted polymer was packed into a 21G stainless‐steel needle and served as an extraction medium. The coated‐fiber needle extraction device was used to extract volatile organic compounds from paints and gasoline effectively. Subsequently, the extracted volatile organic compounds were analyzed by gas chromatography. Calibration curves of gaseous benzene, toluene, ethylbenzene, and o‐xylene in the concentration range of 1–250 μg/L were obtained to evaluate the method, acceptable linearity was attended with correlation coefficients above 0.998. The limit of detection of benzene, toluene, ethylbenzene, and o‐xylene was 11–20 ng/L using the coated‐fiber needle‐trap device. The relative standard deviation of needle‐to‐needle repeatability was less than 8% with an extraction time of 20 min. The loss rates after storage for 3 and 7 days at room temperature were less than 30%.