Solid-phase Microextraction Procedure Research Articles

Polycyclic aromatic hydrocarbon concentrations in gas and particle phases and source determination in atmospheric samples from a semiurban area of Dourados, Brazil.

A headspace solid-phase microextraction (HS-SPME) procedure that employs a PDMS/DVB fiber was developed for the analysis of gas-phase polycyclic aromatic hydrocarbons (PAHs) collected in polyurethane foam (PUF) by gas chromatography (GC) mass spectrometry. The method exhibited good linearity (R (2) > 0.99) and repeatability (4.9-25 %) as well as an impressive detection limit that ranged from 1.1 to 3.3 ng. Twenty-two air samples were collected by high-volume samplers from January to November 2007 in a semiurban area of Dourados (Brazil) and were analyzed for their content of total suspended particulates and PAHs. The PAHs were extracted from the PUF samples using the developed procedure (HS-SPME), and PAHs adsorbed on particulate matter were extracted with dichloromethane/methanol (4:1 [v/v]) in an ultrasonic bath. The values of the total daily concentrations of 16 PAHs determined in the samples ranged from 0.375 to 8.407 ng m(-3). In addition, diagnostic ratios were calculated, showing that the PAHs in the atmosphere at the sampling site originated predominantly from vehicle emissions and the combustion of grass and wood. Hierarchical cluster analysis and principal component analysis were performed as well, the results of which indicated (1) the same sources of PAH identified by the diagnostic ratios and (2) that the sampling days could be categorized into three groups depending on the atmospheric conditions. GC retention indices were also used to identify PAHs, biphenyl (phenylbenzene), and heterocyclic organic compounds (benzofurans) in some of the samples.

Green chromatography determination of fatty acid methyl esters in biodiesel

This work proposes a green, simple and rapid chromatographic methodology for separation and determination of a group of 13 fatty acids methyl esters (FAMEs) by using a capillary gas chromatography with a flame ionization detector. The method was successfully applied for the determination of FAMEs in biodiesel samples from commercial and waste cooking oils, synthesized by homogeneous catalysis. Detection and quantification limits were in the μg L−1 level. Direct injection of sample solution was compared with solid-phase extraction and solid-phase microextraction procedures, giving similar results. The lower analysis time represent considerable improvement compared with other papers. The described methodology is especially suitable for process control applications. The samples analysed showed total contents of FAMEs higher than 96.5%, which verifies the European regulations.

Development and Validation of a Solid-Phase Microextraction Method for the Determination of Total Flavouring Content in Encapsulated Flavouring

A solid-phase microextraction procedure followed by analysis by gas chromatography is proposed to determine total flavouring content in encapsulated flavouring. The method showed a good selectivity, as well as good intraday and interday precision, CVs = 1 % in both cases. The calibration curves were linear at the tested ranges (R = 0.998). The limits of detection and quantification were 17 and 48 g kg−1, respectively. Good recoveries were obtained (95.9–105.4 %). In the ruggedness test, sample temperature, extraction time, sample amount, magnetic stirring and desorption temperature were the factors that stood out as the causing of the greater effects on the analytical results. These results present a solid-phase microextraction (SPME) methodology, which may be applied as a quality control tool for industrial laboratories.

Development and validation of a gas chromatographic method by solid-phase microextraction for the determination of surface flavouring content in encapsulated flavouring

A solid-phase microextraction procedure followed by analysis by gas chromatography is proposed to determine surface flavouring content in encapsulated flavouring. The method showed a good selectivity, as well as good intraday and interday precision, CVs<4% in both cases. The calibration curves were linear at the tested ranges (R=0.998). The limits of detection and quantification were 0.52gkg−1 and 1.57gkg−1, respectively. Good recoveries were obtained (90.8–104.5%). In the ruggedness test, sample amount, pre-extraction time, desorption time and desorption temperature were the factors that stood out as the causing of the greater effects on the analytical results. These results present a SPME methodology, which may be applied as a quality control tool for industrial laboratories.

Preparation of multi-walled carbon nanotubes decorated with Fe3O4 nanoparticles for determination of trace pyrethroid pesticides in water and honey samples

A magnetic carbon nanotube hybrid material was prepared using a chemical co-precipitation method. The Fe3O4 nanoparticles were enclosed onto the surface of the acid multi-walled carbon nanotubes (AMWNTs), and they were identified as Fe3O4/AMWNTs composites. This hybrid materials displayed typical superparamagnetic behavior, good dispersibility, and good adsorption capacity for pyrethroid pesticides. A magnetic solid-phase microextraction (MSPE) procedure based on Fe3O4/AMWNTs composites, combined with gas chromatography, was developed for the quantification of six pyrethroid pesticides in water and honey samples. Several important parameters affecting the extraction efficiency for six pyrethroid pesticides were optimized in sequential order, including ionic strength, extraction time and desorption time. Under the optimized conditions, this method showed wide linearity ranging from 0.5 µg/L to 50 µg/L with correlation coefficients (R2) higher than 0.990. The limits of detection (LODs) ranged from 0.07 µg/L to 0.20 µg/L at a singal-to-noise ratio of 3. The relative standard deviations (RSDs) ranged from 3. 8% to 8. 1%. Satisfactory recoveries (> 78.4%) were obtained for the simultaneous analysis of the six pyrethroid pesticide residues in river water, fish-pond water and two honey samples. This method is sensitive and simple. It can meet the actual requirement for the analysis of trace analytes from environmental water and honey samples.

Sensitive magnetic solid-phase microextraction based on oxide multi-walled carbon-nanotubes for the determination of methylamphetamine and ketamine in human urine and blood

A solid-phase microextraction (MSPE) procedure, combined with gas chromatography-mass spectrometry (GC-MS), was developed for the quantification of two illegal basic drugs in biological samples.

Direct determination of methyl parathion insecticide in rice samples by headspace solid-phase microextraction-gas chromatography-mass spectrometry.

The organophosphorus insecticides, especially those based on methyl parathion as active principle, have been used extensively in the protection of rice in Maranhão State, in the north-east of Brazil. This paper describes the optimisation of a solid-phase microextraction (SPME) procedure in confined atmosphere (headspace, HS) for the determination of methyl parathion in rice organic samples by gas chromatography with mass spectrometry detection (GC/MS). The proposed HS-SPME-GC/MS method has been shown to be appropriate for direct analysis of the insecticide in polished rice, with satisfactory results for the following parameters: linearity (correlation coefficient 0.9985), sensitivity (LOD and LOQ of 0.026 and 0.078 µg kg(-1) respectively), precision (coefficients of variation between 6.1 and 22.4%) and accuracy (recoveries varying from 73.2 to 90.0%). Although the efficiency of the proposed GC/MS does not differ statistically (P < 0.05) from the conventional GC/NPD method, given its low cost, speed and also the fact that a minimum volume of toxic effluent is generated, this method can be considered an on-line procedure based on green chemistry. Thus, the analytical methodology satisfies the minimum requirements for control of residues of such insecticides in rice samples destined for human consumption.

HS-SPME-GC-FID method for detection and quantification of Bacillus cereus ATCC 10702 mediated 2-acetyl-1-pyrroline.

A rapid micro-scale solid-phase micro-extraction (SPME) procedure coupled with gas-chromatography with flame ionized detector (GC-FID) was used to extract parts per billion levels of a principle basmati aroma compound "2-acetyl-1-pyrroline" (2-AP) from bacterial samples. In present investigation, optimization parameters of bacterial incubation period, sample weight, pre-incubation time, adsorption time, and temperature, precursors and their concentrations has been studied. In the optimized conditions, detection of 2-AP produced by Bacillus cereus ATCC10702 using only 0.5 g of sample volume was 85 μg/kg. Along with 2-AP, 15 other compounds produced by B. cereus were also reported out of which 14 were reported for the first time consisting mainly of (E)-2-hexenal, pentadecanal, 4-hydroxy-2-butanone, n-hexanal, 2-6-nonadienal, 3-methoxy-2(5H) furanone and 2-acetyl-1-pyridine and octanal. High recovery of 2-AP (87 %) from very less amount of B. cereus samples was observed. The method is reproducible fast and can be used for detection of 2-AP production by B. cereus.

Determination of some selected pesticide residues in apple juice by solid-phase microextraction coupled to gas chromatography - mass spectrometry

The performance of solid phase microextraction (SPME) for enrichment of pesticides from apple juice was investigated. Samples were diluted with water, extracted by solid-phase microextraction and analysed by gas chromatography using mass-spectrometry detector (MSD) in selected ion monitoring mode (SIM). The method was tested for the following pesticides used mostly in fruit culturing at Slovakia: tebuthylazine, fenitrothion, chlorpyrifos, myclobutanil, cyprodinil, phosalone, pyrimethanil, tebuconazole, kresoxim-methyl, methidathion, penconazole. All pesticides were extracted with polydimethylsiloxane fibre 100 μm thickness. The linear concentration range of application was 0.05 μg dm−3–10 μg dm−3. The method described provides detectabilities complying with the maximum residue levels (MRLs) set by regulatory organizations for pesticides in apple juice matrices. The solvent – free SPME procedure was found to be quicker and more cost effective then the solvent extraction methods commonly used.

Application of Solid-Phase Microextraction for the Analysis of Aroma Compounds from Pineapple Fruit

An analytical method of solid-phase microextraction (SPME) was developed for pineapple aroma volatile compounds. Different sample preparation procedures involving SPME fibres, including the addition of sodium chloride, extraction time, and temperature, were evaluated to optimise the method. For the optimised method, 6.5 g of ground pineapple flesh was placed in a 20 mL headspace vial with 1 g of sodium chloride; a 65 μm polydimethylsiloxane/divinylbenzene fibre was used for extraction at 50°C for 40 min with continuous stirring. The method was validated by determining its repeatability and recovery. The relative standard deviations for the pineapple aroma compounds were 5.48-11.02%. The average method recovery was 99.13%. The results demonstrate that this SPME procedure is suitable as a simple, rapid, and solvent-free extraction technique for the analysis of pineapple aroma volatile compounds. Using this method, 15 volatile compounds were identified, and the amount was 1019.78 μg.kg−1 in pineapple cv. Shenwan, including seven esters, one terpene, two aldehydes, one ketone, two lactones, one alcohol, and one hydrocarbon. A tentative study to estimate the contribution of the identified compounds to the aroma of the pineapple variety based of their odour activity values indicated four compounds that were characteristic aroma compounds, including methyl hexanoate, δ-octalactone, decanal, and geranyl acetone.

Development of a multi-preservative method based on solid-phase microextraction–gas chromatography–tandem mass spectrometry for cosmetic analysis

A simple methodology based on solid-phase microextraction (SPME) followed by gas chromatography–tandem mass spectrometry (GC–MS/MS) has been developed for the simultaneous analysis of different classes of preservatives including benzoates, bronidox, 2-phenoxyethanol, parabens, BHA, BHT and triclosan in cosmetic products. In situ acetylation and subsequent organic modifier addition have been successfully implemented in the SPME process as an effective extractive strategy for matrix effect compensation and chromatographic performance improvement. Main factors affecting SPME procedure such as fiber coating, sampling mode, extraction temperature and salt addition (NaCl) were evaluated by means of a 3×23–1 factorial experimental design. The optimal experimental conditions were established as follows: direct solid-phase microextraction (SPME) at 40°C and addition of NaCl (20%, w/v), using a DVB/CAR/PDMS fiber coating. Due to the complexity of the studied matrices, method performance was evaluated in a representative variety of both rinse-off and leave-on samples, demonstrating to have a broad linear range (R2>0.9964). In general, quantitative recoveries (>85% in most cases) and satisfactory precision (RSD<13% for most of compounds) were obtained, with limits of detection (LODs) well below the maximum authorized concentrations established by the European legislation. One of the most important achievements of this work was the use of external calibration with cosmetic-matched standards to accurately quantify the target analytes. The validated methodology was successfully applied to the analysis of different types of cosmetic formulations including body milks, moisturizing creams, deodorants, sunscreen, bath gel, dental cream and make-up products amongst others, demonstrating to be a reliable multi-preservative methododology for routine control.

Effects of Soybean Pectin Gel on Flavor Compounds Variation of Cheddar Cheeses during Ripening

In this manuscript, flavor compounds development of Cheddar Cheese with addition of soybean pectin gel was investigated during ripening. A rapid and simple Solid-Phase Microextraction (SPME) procedure was used for identifying and classifying the volatile compounds. The result showed that addition of soybean pectin gel to cheese had similar flavor profiles with full-fat cheeses. Higher levels of acid volatile compounds and aldehydes were obtained in comparison with experimental cheese. Results simultaneously indicated that experimental cheeses contained high concentrations of volatile amine as soybean pectin gel promoting the volatile substances.

Optimization of Solid Phase Microextraction Procedure Followed by Gas Chromatography with Electron Capture Detector for Pesticides Butachlor and Chlorpyrifos

In this study, headspace solid phase microextraction (HS-SPME) followed by gas chromatography using electron capture detection system (GC-ECD) were developed for the determination of chloraacetanilide (butachlor) and chlorpyrifos presented in biological samples. Different parameters affecting the extraction procedure were optimized including extraction time (30 minutes), extraction temperature (80°C), sample volume (3 mL), sample pH (2), added NaCl (0.3 gram) and sample stirring rate (400 rpm). Different concentrations of 1 - 100 ng/ml were applied for butachlor and a linear calibration curve was obtained. Furthermore, a similar linearity was obtained for chlorpyrifos, using a concentration range of 1 - 250 ng/ml. The limit of detection (LOD) obtained for butachlor and chlorpyrifos were 0.088 and 0.53 ng/ml respectively. The optimized methods for both compounds were validated using two concentrations of 25 and 50 ng/ml in spiked urine samples. Obtained recoveries of spiked urine samples were 83.06% - 99.8% with RSD of lower than 11%. Optimized technique was simple, inexpensive, solvent free and fast in comparison with other conventional methods and had compatibility with the chromatographic analytical system. This method offers low detection limits to analyze pesticides in urine samples that are very important in the exposure monitoring in occupational health.

Evaluation of a Headspace Solid‐Phase Microextraction Method for the Analysis of Ignitable Liquids in Fire Debris

The chemical analysis of fire debris represents a crucial part in fire investigations to determine the cause of a fire. A headspace solid-phase microextraction (HS-SPME) procedure for the detection of ignitable liquids in fire debris using a fiber coated with a mixture of three different sorbent materials (Divinylbenzene/Carboxen/Polydimethylsiloxane, DVB/CAR/PDMS) is described. Gasoline and diesel fuel were spiked upon a preburnt matrix (wood charcoal), extracted and concentrated with HS-SPME and then analyzed with gas chromatography/mass spectrometry (GC/MS). The experimental conditions--extraction temperature, incubation and exposure time--were optimized. To assess the applicability of the method, fire debris samples were prepared in the smoke density chamber (SDC) and a controlled-atmosphere cone calorimeter. The developed methods were successfully applied to burnt particleboard and carpet samples. The results demonstrate that the procedure that has been developed here is suitable for detecting these ignitable liquids in highly burnt debris.

Preparation and application of a polythiophene solid‐phase microextraction fiber for the determination of endocrine‐disruptor pesticides in well waters

A robust solid-phase microextraction fiber was fabricated by electropolymerization of thiophene on a stainless steel wire. This fiber was applied for the determination of endocrine-disruptor pesticides, namely, chlorpyrifos, penconazole, procymidone, bromopropylate, and λ-cyhalothrin in well waters by a headspace solid-phase microextraction procedure. Operational parameters, namely, pH, sample volume, adsorption temperature and time, desorption temperature, stirring rate, and salt amount were optimized as 7.0, 8 mL, 70°C and 20 min, 250°C, 600 rpm, and 0.3 g/mL, respectively. The separation power of GC was coupled with the excellent sensitivity of the developed fiber enabling us to determine pesticide mixtures simultaneously in a ng/mL range. The LOD was in the range of 0.02-0.64 ng/mL. The method was successfully applied for the selective and sensitive determination of target pesticides in well water samples with acceptable recovery values (92-110%). The polythiophene fiber gives satisfactory results compared with commercial fibers. Commonly used pesticides with different polarities were chosen as representative compounds to search the applicability of the fiber for well water analysis collected from vineyards.

Combined solid‐phase microextraction and high‐performance liquid chromatography with ultroviolet detection for simultaneous analysis of clenbuterol, salbutamol and ractopamine in pig samples

A simple and sensitive method based on the combination of solid-phase microextraction (SPME) and high-performance liquid chromatography with ultroviolet detection was developed for the simultaneous determination of clenbuterol, salbutamol and ractopamine in pig samples. Parameters of the SPME procedure affecting extraction efficiency, such as the type of fiber, extraction time, extraction temperature, ion strength, pH of sample and stirring rate, were optimized. The developed method was validated according to the International Conference on Harmonization guidelines. The calibration curves were linear over a range of 0.5-50 µg/L for clenbuterol and ractopamine, and 0.2-20 µg/L for salbutamol. The limits of detection were 0.1 µg/L for clenbuterol, 0.05 µg/L for salbutamol and 0.1 μg/L for ractopamine, respectively. The averages of intra- and inter-day accuracy ranged from 79.8 to 92.4%. The intra-day and inter-day precision were below 9.6% for the three analytes. This method exhibited the advantages of simplicity, rapidity and low solvent consumption, and was suitable for the monitoring of β2 -agonists residue in pig samples.

Influence of matrix on suitability of four methods for organochlorine pesticide analysis in waters

The monitoring of organochlorine pesticides has raised a great concern in the last years due to their toxicity (some of them are carcinogenic and endocrine disruptor compounds) and persistence. European Directive 2008/105/EC establishes very restrictive levels for organochlorine pesticides in surface waters. Therefore, simple, fast, highly sensitive and low cost analytical methods are required to detect and quantify these pollutants in water. In the present work, four procedures for extraction and determination are proposed and compared for the analysis of 28 organochlorine pesticides in tap, surface and sea waters. The suitability of each method of analysis was evaluated for each kind of water. The extraction methods proposed were: two solid-phase extraction methods using C18 laminar disk and Oasis HLB cartridges, a solid-phase microextraction procedure using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre, and a micro liquid–liquid extraction procedure using ethyl acetate as solvent. Determination of pesticides was performed by large volume on-column injector-gas chromatography-electron capture detection (LVOCI-GC-ECD), splitless-GC-ECD and GC-MS (mass spectrometry). All methods present a good sensitivity with method detection limits lower than 10 ng L−1, good accuracy with recoveries between 75 and 120% (with some exceptions) and good precision (relative standard deviations <15%), according to the Commission Decision 2002/657/EC criteria. The advantages and disadvantages of each method are discussed in terms of the green chemistry principles, the figures of merit and the matrix effect. This work tries to be a useful guidance for routine and control analysis laboratories.

Headspace Solid Phase Microextraction Procedure for the Detection of Polychlorinated Biphenyls in Seawater Sample

Headspace solid phase microextraction combined with gas chromatography (HS-SPME–GC) method has been studied for determination of 7 polychlorinated biphenyls (PCBs) in seawater samples. To perform the HS-SPME polydimethylsiloxane (PDMS) (7, 30 and 100 µm film thickness) fibers were compared on the basis of their absorption capacities for the selected compounds, and PDMS 100 µm film thickness was selected. The influence of various parameters on PCBs extraction efficiency by HS-SPME was studied using GC-electron capture detector (ECD) compared with solid phase. The performance of proposed HS-SPME–GC methodology with respect to linearity, reproducibility and limit of detection (LOD) was evaluated by water spiked with target compounds. The linear range of most compounds was found to be between 0.1 and 100 µgL−1 and the limits of detection were between 15.2 and 63.8 ngL−1. The reproducibility of the method (n = 6), expressed as relative standard deviation (RSD), was between 4 and 10%. Finally, developed procedure was applied to determine selected PCBs in seawater samples.

A novel method to prepare monolithic molecular imprinted polymer fiber for solid‐phase microextraction by microwave irradiation†

In this paper, a new approach to prepare monolithic molecularly imprinted polymer (MIP) fibers for solid-phase microextraction is proposed with the help of microwave irradiation. Imprinting polymerization was carried out within silica capillaries in 4.5 min, using dimethyl phthalate (DMP) as a template molecular, α-methacrylic acid as a functional monomer and ethylene dimethacrylate as a crosslinker, acetonitrile as the porogenic solvent. The synthesis was optimized by varying the ratio of template/monomer and different volume of porogen. The resulted MIP fibers were obtained after silica being etched away with a controlled length of 1 cm, and subsequently characterized by SEM. In order to increase the selective extraction of DMP, factors affecting the extraction including extraction time, salt concentration, desorption time, and desorption solvents were investigated for solid-phase microextraction procedures in detail. The selectivity coefficients, defined as the extraction amount ratio of MIP to its nonimprinting fiber, were 5.6, 2.6, and 1.4 for DMP and its counterpart including dibutyl phthalate and di-n-octylo-phthalate, respectively. The resulted fibers were also applied to detect DMP, dibutyl phthalate, and di-n-octylo-phthalate in bottled beverage samples coupled to HPLC and resulted in relative recoveries of up to 73.8-98.5%, respectively.

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.