Application of solid-phase microextraction and gas chromatography-mass spectrometry for the determination of chlorophenols in leather

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

Sorptive extraction with in-sample acetylation for gas chromatography-mass spectrometry determination of ethylphenol species in wine samples

An inexpensive and effective sample preparation procedure for the determination of three ethylphenolic off-flavours (4-ethylphenol, 4-ethylguaiacol and 4-ethylcathecol) in wine samples is presented. Analytes were in situ acetylated and concentrated using a disposable silicone sorbent (DSS) exposed to the diluted sample. After that, the analytes were recovered with ethyl acetate and determined by gas chromatography with mass spectrometry. The influence of different parameters (volume of acetic anhydride, basic catalyst, ionic strength, sorbent format, sampling mode and extraction time) on the efficiency of derivatization and extraction steps is discussed. Under optimized conditions, 2 mL of wine were diluted with 15 mL of an aqueous solution of potassium bicarbonate (5%, m/v) in a 22 mL vessel, containing 2 g of sodium chloride. The volume of acetic anhydride and the extraction time were set at 90 μL and 2 h, and the extraction was carried out at room temperature (20±2°C). Analytes were concentrated using a silicone disc (5 mm diameter × 0.5 mm thickness) and further desorbed with 0.2 mL of ethyl acetate. The achieved limits of quantification (LOQs), defined as the concentration of each compound providing a signal 10 times higher than the baseline noise, stayed between 5 and 15 ng mL(-1). The method provided a linear response range of up to 5000 ng mL(-1) and relative recoveries from 91% to 116%. The 4-ethylphenol off-flavour was detected in most red wine samples at concentrations of up to 2700 ng mL(-1).     

Ultrasound-assisted emulsification microextraction coupled with gas chromatography–mass spectrometry using the Taguchi design method for bisphenol migration studies from thermal printer paper, toys and baby utensils

The optimization of a clean procedure based on ultrasound-assisted emulsification liquid-liquid microextraction for the sensitive determination of four bisphenols is presented. The miniaturized technique was coupled with gas chromatography-mass spectrometry after derivatization by in situ acetylation. The Taguchi experimental method, an orthogonal array design, was applied to find the optimal combination of seven factors (each factor at three levels) influencing the emulsification, extraction and collection efficiency, namely acetic anhydride volume, sodium phosphate concentration, carbon tetrachloride volume, aqueous sample volume, sodium chloride concentration and ultrasound power and application time. A second factorial design was applied with four factors and five levels for each factor, 25 experiments being performed in this instance. The matrix effect was evaluated, and it was concluded that sample quantification can be done by calibration with aqueous standards. The detection limits ranged from 0.01 to 0.03 ng mL(-1) depending on the compound. The environmentally friendly sample pretreatment procedure was applied to study the migration of the bisphenols from different types of samples: thermal printer paper, compact discs, digital versatile discs, small tight-fitting waistcoats, baby's bottles, baby bottle nipples of different materials and children's toys.     

Rapid determination of bisphenol A in drinking water using dispersive liquid‐phase microextraction with in situ derivatization prior to GC‐MS

This paper described a novel approach for the determination of bisphenol A by dispersive liquid‐phase microextraction with in situ acetylation prior to GC‐MS. In this derivatization/extraction method, 500 μL acetone (disperser solvent) containing 30.0 μL chlorobenzene (extraction solvent) and 30.0 μL acetic anhydride (derivatization reagent) was rapidly injected into 5.00 mL aqueous sample containing bisphenol A and K₂CO₃ (0.5% w/v). Within a few seconds the analyte was derivatized and extracted at the same time. After centrifugation, 1.0 μL of sedimented phase containing enriched analyte was determined by GC‐MS. Some important parameters, such as type and volume of extraction and disperser solvent, volume of acetic anhydride, derivatization and extraction time, amount of K₂CO₃, and salt addition were studied and optimized. Under the optimum conditions, the LOD and the LOQ were 0.01, 0.1 μg/L, respectively. The experimental results indicated that there was linearity over the range 0.1–50 μg/L with coefficient of correlation 0.9997, and good reproducibility with RSD 3.8% (n = 5). The proposed method has been applied for the analysis of drinking water samples, and satisfactory results were achieved.     

Optimization of a microwave-assisted extraction method for the analysis of polychlorinated biphenyls in ash samples

An alternative method for the extraction of polychlorinated biphenyls (PCBs) in ash samples, which is less time and solvent consuming than Soxhlet extraction, is presented. A study was carried out to evaluate the possibilities of microwave-assisted extraction (MAE) to determine exactly which parameters affect the efficiency of the process, since direct extrapolation of extraction conditions for PCBs in other solid matrices, failed when applied to coplanar congeners in ash samples. Influence of the organic solvent on the yield of the extraction was first evaluated using two ash samples with different percentages of carbon. Once the extraction solvent was fixed, the effects of solvent volume, extraction temperature and extraction time were investigated using an experimental design. It was found that the volume of organic solvent played a more important role in the extraction efficiency than the other factors. In the optimal conditions microwave extractions were performed at 110 degrees C. for 10 min and using 30 ml of toluene. Recoveries higher than 80% were obtained for all the highly chlorinated congeners. including coplanar species, in a spiked ash sample containing a relatively high concentration of carbon. The proposed method was also applied to the determination of PCBs in a reference material of urban dust. Recoveries were similar to those obtained for spiked ash samples.     

Solvent‐assisted dispersive micro‐SPE by using aminopropyl‐functionalized magnetite nanoparticle followed by GC‐PID for quantification of parabens in aqueous matrices

In this research, solvent‐assisted dispersive micro‐SPE was introduced as a simple modified technique for the determination of parabens in water and cosmetic samples. Aminopropyl‐functionalized magnetite nanoparticles (MNPs) were successfully synthesized and applied. GC with photoionization detector was used for the separation and detection of parabens. In this method, hexylacetate (15 μL) as a solvent and aminopropyl‐functionalized MNPs (5 μg) as a sorbent were added to an aqueous sample (10 mL) and then the sample was sonicated. Dispersed magnetite was collected in the bottom of the conical tube by using a strong magnet and then ACN was added as a desorption solvent. Forty microliters of this solvent was transferred into a microvial and then acetic anhydride and pyridine were added, thus derivatization was performed by acetic anhydride. After evaporation, 1 μL of derivatized sample was injected into a gas chromatograph for analysis. Several important parameters, such as kind of organic solvent, desorption solvent and volume, amount of aminopropyl‐functionalized MNPs and effect of salt addition were investigated. Under optimum conditions, the limits of detection achieved were between 50 and 300 ng/L, with RSDs (n = 5) lower than 8%. Under the optimum conditions, the enrichment factors ranged from 217 to 1253 and the extraction recoveries ranged from 10 to 62%. The recoveries were obtained for the analytes in river water and mouthwash solution and hand cream in the range of 87–103%. The advantages of proposed method are simplicity of operation, rapidity, high extraction yields, and environmental friendly character.     

Evaluation of dispersive liquid-liquid microextraction for the simultaneous determination of chlorophenols and haloanisoles in wines and cork stoppers using gas chromatography-mass spectrometry

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) was evaluated for the simultaneous determination of five chlorophenols and seven haloanisoles in wines and cork stoppers. Parameters, such as the nature and volume of the extracting and disperser solvents, extraction time, salt addition, centrifugation time and sample volume or mass, affecting the DLLME were carefully optimized to extract and preconcentrate chlorophenols, in the form of their acetylated derivatives, and haloanisoles. In this extraction method, 1mL of acetone (disperser solvent) containing 30μL of carbon tetrachloride (extraction solvent) was rapidly injected by a syringe into 5mL of sample solution containing 200μL of acetic anhydride (derivatizing reagent) and 0.5mL of phosphate buffer solution, thereby forming a cloudy solution. After extraction, phase separation was performed by centrifugation, and a volume of 4μL of the sedimented phase was analyzed by GC-MS. The wine samples were directly used for the DLLME extraction (red wines required a 1:1 dilution with water). For cork samples, the target analytes were first extracted with pentane, the solvent was evaporated and the residue reconstituted with acetone before DLLME. The use of an internal standard (2,4-dibromoanisole) notably improved the repeatability of the procedure. Under the optimized conditions, detection limits ranged from 0.004 to 0.108ngmL(-1) in wine samples (24-220pgg(-1) in corks), depending on the compound and the sample analyzed. The enrichment factors for haloanisoles were in the 380-700-fold range.     

Evaluation of matrix solid‐phase dispersion extraction for the determination of polycyclic aromatic hydrocarbons in household dust with the aid of experimental design and response surface methodology

A simple, fast, and inexpensive procedure for sample preparation based on matrix solid‐phase dispersion was developed for the determination of Environmental Protection Agency 16 priority polycyclic aromatic hydrocarbons in indoor dust samples. Parameters that affect the extraction efficiency such as type of dispersant, elution solvent, and solvent volume were evaluated and optimized with the aid of experimental design and response surface methodology. Analysis was performed by HPLC coupled with UV‐Vis diode array detector (UV‐DAD). For verification, a GC coupled with a mass spectrometer in SIM mode was also applied. Recoveries obtained were from 53 to 120% for all target analytes with detection limits ranging from 0.2 to 10 ng/g and 0.2 to 2 ng/g for LC‐UV‐DAD and GC‐MS, respectively. The optimized method was used for the analysis of 11 household dust samples collected from private houses.     

Determination of atranol and chloroatranol in perfumes using simultaneous derivatization and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A new analytical method based on simultaneous derivatization and dispersive liquid–liquid microextraction (DLLME) followed by gas chromatography–mass spectrometry (GC–MS), for the determination of the allergenic compounds atranol and chloroatranol in perfumes, is presented. Derivatization of the target analytes by means of acetylation with anhydride acetic in carbonate buffer was carried out. Thereby volatility and detectability were increased for improved GC–MS sensitivity. In addition, extractability by DLLME was also enhanced due to a less polar character of the solutes. A liquid–liquid extraction was performed before DLLME to clean up the sample and to obtain an aqueous sample solution, free of the low polar matrix from the essential oils, as donor phase. Different parameters, such as the nature and volume of both the extraction and disperser solvents, the ionic strength of the aqueous donor phase or the effect of the derivatization reagent volume, were optimized. Under the selected conditions (injection of a mixture of 750 μL of acetone as disperser solvent, 100 μL of chloroform as extraction solvent and 100 μL of anhydride acetic as derivatization reagent) the figures of merit of the proposed method were evaluated. Limits of detection in the low ng mL⁻¹ range were obtained. Matrix effect was observed in real perfume samples and thus, standard addition calibration is recommended.     

Microwave-assisted extraction and mild saponification for determination of organochlorine pesticides in oyster samples

A sample-preparation procedure (extraction and saponification) using microwave energy is proposed for determination of organochlorine pesticides in oyster samples. A Plackett-Burman factorial design has been used to optimize the microwave-assisted extraction and mild saponification on a freeze dried sample spiked with a mixture of aldrin, endrin, dieldrin, heptachlor, heptachorepoxide, isodrin, transnonachlor, p, p'-DDE, and p, p'-DDD. Six variables: solvent volume, extraction time, extraction temperature, amount of acetone (%) in the extractant solvent, amount of sample, and volume of NaOH solution were considered in the optimization process. The results show that the amount of sample is statistically significant for dieldrin, aldrin, p, p'-DDE, heptachlor, and transnonachlor and solvent volume for dieldrin, aldrin, and p, p'-DDE. The volume of NaOH solution is statistically significant for aldrin and p, p'-DDE only. Extraction temperature and extraction time seem to be the main factors determining the efficiency of extraction process for isodrin and p, p'-DDE, respectively. The optimized procedure was compared with conventional Soxhlet extraction.     

Ultrasound-assisted emulsification-microextraction of phenolic preservatives in water

Simultaneous ultrasound-assisted emulsification-microextraction (USAEME) and derivatization combined with gas chromatography-tandem mass spectrometry (GC-MS/MS) is proposed for the first time for the analysis of parabens, triclosan and related phenols in water samples. In situ acetylation was successfully applied for the derivatization of target compounds with high efficiency using non-expensive reagents. The proposed method exhibits many advantages such as simplicity, efficiency, low cost, and minimum solvent consumption. In addition, the whole analytical process, including sample preparation and determination, is performed in only 20 min.A multifactorial experimental design was employed to study and optimize the main variables potentially affecting the microextraction and derivatization processes (extraction solvent, phase ratio, sodium chloride concentration, extraction time, and acetic anhydride volume).The performance of the method was studied in terms of accuracy, linearity, precision, and enrichment factor. Quantitative recoveries (≥85%) were obtained for all target compounds, and method precision was also satisfactory (RSD ≤ 13%) even for complex samples. Enrichment factors ranging from 100 to 200 were obtained, allowing achieving limits of detection at the low picogram per millilitre for most of the target compounds.Several real samples, including wastewaters, river waters and swimming pool water, were analyzed. Since matrix effects were not observed, quantification can easily be performed using external calibration with acetylated standards, allowing a high sample throughput.     

Fast ultrasound‐assisted extraction combined with LC–MS/MS of perfluorinated compounds in manure

A fast analytical method for the determination of perfluorinated compounds in poultry manure by LC–MS/MS was developed. The extraction was carried out by ultrasound‐assisted extraction of 1 g of sample, during 2 × 15 min using low volume (5.5 mL) of a mixture of methanol and acetonitrile. An efficient extraction of perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl sulfonamides from poultry manure was obtained with recoveries higher than 81%. The cleanup of extracts was carried out by dispersive SPE. The validation of the proposed method showed the suitability of this procedure to determine perfluorinated compounds in poultry manure with detection limits in the range of 0.44–2.12 ng/g, depending on the target compound. In comparison with previously published methods, the miniaturization of the sample preparation method with ultrasound‐assisted extraction together with the use of a core‐shell column permit a lower consumption of organic solvents and a fast analysis of perfluorinated compounds. Manure samples obtained from Spanish commercial farms were analyzed and low perfluorinated compounds levels were found, which may be originated by dietary or environmental exposure. The highest concentrations measured corresponded to the perfluoroalkyl sulfonates, which varied from 8.2 to 35.9 ng/g.     

Analyses of polychlorinated biphenyls in waters and wastewaters using vortex-assisted liquid-liquid microextraction and gas chromatography-mass spectrometry

A method was developed for viable and rapid determination of seven polychlorinated biphenyls (PCBs) in water samples with vortex-assisted liquid-liquid microextraction (VALLME) using gas chromatography-mass spectrometry (GC-MS). At first, the most suitable extraction solvent and extraction solvent volume were determined. Later, the parameters affecting the extraction efficiency such as vortex extraction time, rotational speed of the vortex, and ionic strength of the sample were optimized by using a 2(3) factorial experimental design. The optimized extraction conditions for 5 mL water sample were as follows: extractant solvent 200 μL of chloroform; vortex extraction time of 2 min at 3000 rpm; centrifugation 5 min at 4000 rpm, and no ionic strength. Under the optimum condition, limits of detection (LOD) ranged from 0.36 to 0.73 ng/L. Mean recoveries of PCBs from fortified water samples are 96% for three different fortification levels and RSDs of the recoveries are below 5%. The developed procedure was successfully applied to the determination of PCBs in real water and wastewater samples such as tap, well, surface, bottled waters, and municipal, treated municipal, and industrial wastewaters. The performance of the proposed method was compared with traditional liquid-liquid extraction (LLE) of real water samples and the results show that efficiency of proposed method is comparable to the LLE. However, the proposed method offers several advantages, i.e. reducing sample requirement for measurement of target compounds, less solvent consumption, and reducing the costs associated with solvent purchase and waste disposal. It is also viable, rapid, and easy to use for the analyses of PCBs in water samples by using GC-MS.     

Rapid determination of alkylphenols in aqueous samples by in situ acetylation and microwave-assisted headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry

A rapid and solvent‐free procedure for the determination of 4‐tert‐octylphenol and 4‐nonylphenol isomers in aqueous samples is described. The method involves in‐situ acetylation and microwave‐assisted headspace solid‐phase microextraction prior to their determination using gas chromatography–ion trap mass spectrometry operated in the selected ion storage mode. The dual experimental protocols to evaluate the effects of various derivatization and extraction parameters were investigated and the conditions optimized. Under optimized conditions, 300 μL of acetic anhydride mixed with 1 g of potassium hydrogencarbonate and 2 g of sodium chloride in a 20 mL aqueous sample were efficiently extracted by a 65 μm polydimethylsiloxane‐divinylbenzene fiber that was located in the headspace when the system was microwave irradiated at 80 W for 5 min. The limits of quantitation were 5 and 50 ng/L for 4‐tert‐octylphenol and 4‐nonylphenol isomers, respectively. The precision for these analytes, as indicated by relative standard deviations, were less than 8% for both intra‐ and inter‐day analysis. Accuracy, expressed as the mean extraction recovery, was between 74 to 88%. A standard addition method was used to quantitate 4‐tert‐octylphenol and 4‐nonylphenol isomers, and the concentrations ranged from 120 to 930 ng/L in various environmental water samples.     

GC-MS determination of parabens,triclosan and methyl triclosan in water by in situ derivatisation and stir-bar sorptive extraction

Stir-bar sorptive extraction in combination with an in situ derivatisation reaction and thermal desorption–gas chromatography–mass spectrometry was successfully applied to determine parabens (methylparaben, isopropylparaben, n-propylparaben, butylparaben and benzylparaben), triclosan and methyltriclosan in water samples. This approach improves both the extraction efficiency and the sensitivity in the GC in a simple way since the derivatisation reaction occurs at the same time as the extraction procedure. The in situ derivatisation reaction was carried out with acetic anhydride under alkaline conditions. Thermal desorption parameters (cryofocusing temperature, desorption flow, desorption time, desorption temperature) were optimised using a Box–Behnken experimental design. All the analytes gave recoveries higher than 79%, except methylparaben (22%). The method afforded detection limits between 0.64 and 4.12 ng/L, with good reproducibility and accuracy values. The feasibility of the method for the determination of analytes in water samples was checked in tap water and untreated and treated wastewater.     

Simultaneous determination of butyltin and phenyltin species in sediments using ultrasound-assisted leaching

A fast and simple procedure is presented for the simultaneous leaching of butyl (mono, di and tributyl) and phenyl organotin species from sediment samples. Leached compounds are further ethylated with sodium tetraethylborate in aqueous medium, and analyzed by gas chromatography. After testing the stability of triphenyltin under different extraction conditions, ultrasound-assisted leaching at room temperature in the presence of acetic acid was been proposed as an extraction procedure compatible with the simultaneous determination of phenyl- and butyltin compounds in sediments. Recoveries between 70 and 90% were obtained for phenyl species in spiked samples prepared in the laboratory. Results for butyltin species were validated by use of the reference material PACS-2. Quantification limits, using GC-MIP-AES as measurement technique, were approximately 5-10 ng g(-1). Precision in the consecutive analysis of three sediment samples varied between 3 and 10%.     

Optimisation and comparison of microwave-assisted extraction and Soxhlet extraction for the determination of polychlorinated biphenyls in soil samples using an experimental design approach

Optimisation of microwave-assisted extraction (MAE) for the extraction of polychlorinated biphenyls (PCBs) from soil samples has been accomplished using an experimental design approach. Variables studied have been: percentage of acetone (v/v) in an acetone:n-hexane mixture, solvent volume, extraction time, microwave power and pressure inside the extraction vessel. Five samples of a certified soil (CRM 481) have been extracted under the optimum conditions of the developed method and the results have been compared to those obtained by Soxhlet extraction. Good recoveries (>95%) have been obtained for all the PCBs studied. All extracts have been analysed by gas chromatography/mass spectrometry (GC/MS) and an optimum determination method for the electron impact mass spectrometric (EIMS) has also been developed.     

微波辅助萃取-气相色谱质谱法检测生物体内的多溴联苯醚

建立了微波辅助萃取-气相色谱质谱法测定生物样品中的多溴联苯醚(PBDEs)的方法,优化了萃取剂的种类、萃取剂用量、萃取时间等微波萃取条件和GC-MS仪器分析条件。正己烷-丙酮混合溶剂提取后,经实验室自制的多层硅胶柱分离纯化,用气相色谱-质谱进行测定,该方法基质加标回收率在60%～77%之间,相对标准偏差在11%～18%之间,方法的检测限为0.03～0.20ng/g,适用于生物样品中PBDEs的测定。     

Determination of organophosphorous pesticides in the ppq range using a simple solid-phase extraction method combined with dispersive liquid-liquid microextraction

Solid-phase extraction combined with dispersive liquid-liquid microextraction (SPE-DLLME) was applied for the extraction of six organophosphorous pesticides (OPPs) in water samples. The analytes considered in this study were determined by gas chromatography with mass spectrometry and included prophos, diazinon, chlorpyrifos methyl, methyl parathion, fenchlorphos and chlorpyrifos. Several extraction conditions (extraction solvent and elution/dispersion solvents nature, extraction solvent volume, elution solvent volume, water volume and sample volume) were tested for SPE-DLLME with these analytes and the best results were obtained using carbon tetrachloride as the extraction solvent and acetone as the elution/dispersion solvent. Calibration curves for the determination of OPPs in water samples were constructed in the concentration range of 10-100 ng/L. Limits of detection (LODs) ranged from 38 to 230 pg/L values that are below the maximum admissible level for drinking water (100 ng/L). Relative standard deviations (RSD) were between 8.6 and 10.4% for a fortification level of 100 ng/L. At the same fortification level, the relative recoveries (R.R.) of tap, well and irrigation water samples were in the range of 30.2-97.1%.     

Development and application of chemometric-assisted dispersive liquid-liquid microextraction for the determination of suspected fragrance allergens in water samples

A simple and green method based on dispersive liquid-liquid microextraction, mated to chemometrics and followed by mass spectrometric detection for the determination of suspected fragrance allergens in water samples is developed and assessed in this work. Volume of extraction and disperser solvent, pH, ionic strength, extraction time, sample volume, as well as centrifugation time were initially optimized in a fractional factorial design. The obtained significant factors were optimized by using a central composite design and the quadratic model between the dependent and the independent variables was built. The obtained optimal conditions were: aqueous sample of 3.8 mL, 100 μL chloroform, 1.40 mL acetone, 4 min centrifugation time, natural pH containing 5% (w/v) NaCl, and centrifugation speed 4000 rpm. Method proved to be linear over a wide range of concentration for all analytes with R(2) between 0.9807 and 0.9959. The repeatability and reproducibility of the proposed method, expressed as relative standard deviation, varied between 3-13% and 4-16%, respectively. The limits of detection ranged from 0.007 to 1.0 μg L(-1) . The recommended method was applied to water samples including baby bath as well as swimming pool water samples and was compared with a previously reported method.