Direct Solid-phase Microextraction Research Articles

Gas Chromatography-Mass Spectrometry-Based Analyses of Fecal Short-Chain Fatty Acids (SCFAs): A Summary Review and Own Experience.

The gut microbiome, crucial to human health, changes with age and disease, and influences metabolic profiles. Gut bacteria produce short-chain fatty acids (SCFAs), essential for maintaining homeostasis and modulating inflammation. Dysbiosis, commonly due to poor diet or lifestyle, disrupts the integrity of the intestinal barrier and may contribute to conditions such as obesity, diabetes, and non-alcoholic fatty liver disease (NAFLD). Analytical methods such as gas chromatography-mass spectrometry (GC/MS) are vital for SCFA analysis, with various preparation and storage techniques improving the accuracy. Advances in these methods have improved the reliability and sensitivity of SCFA quantification, which is crucial for the identification of disease biomarkers. Evidence from GC/MS-based studies has revealed that accurate SCFA quantification requires meticulous sample preparation and handling. The process begins with the extraction of SCFAs from biological samples using methods such as direct solvent extraction or solid-phase microextraction (SPME), both of which require optimization for maximum recovery. Derivatization, which chemically modifies SCFAs to enhance volatility and detectability, is a crucial step, typically involving esterification or silylation. Following this, the cleanup process removes impurities that might interfere with the analysis. Although recent advances in GC/MS technology have significantly improved SCFA-detection sensitivity and specificity, proper sample storage, with acid preservatives and the avoidance of repeated thawing, is essential for maintaining SCFA integrity.

Monitoring Poly(methyl methacrylate) and Polyvinyl Dichloride Micro/Nanoplastics in Water by Direct Solid-Phase Microextraction Coupled to Gas Chromatography-Mass Spectrometry.

A simple, sustainable, and sensitive monitoring approach of micro/nanoplastics (MNPs) in aqueous samples is crucial since it helps in assessing the extent of contamination and understanding the potential risks associated with their presence without causing additional stress to the environment. In this study, a novel strategy for qualitative and quantitative determination of MNPs in water by direct solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was proposed for the first time. Spherical poly(methyl methacrylate) (PMMA) and irregularly shaped polyvinyl dichloride (PVDC) were used to evaluate the feasibility and performance of the proposed method. The results demonstrated that both PMMA and PVDC MNPs were efficiently extracted by the homemade SPME coating of nitrogen-doped porous carbons (N-SPCs) and exhibited sufficient thermal decomposition in the GC-MS injection port. Excellent extraction performances of N-SPCs coating for MNPs are attributed to hydrophobic cross-linking, electrostatic forcing, hydrogen bonding, and pore trapping. Methyl methacrylate was identified as the marker for PMMA, while 1,3-dichlorobenzene and 1,3,5-trichlorobenzene were the indicators for PVDC. Under the optimal extraction and decomposition conditions, the proposed method exhibited ultrahigh sensitivity, with a limit of detection of 0.0041 μg/L for PMMA and 0.0054 μg/L for PVDC. Notably, a programmed temperature strategy for the GC-MS injector was developed to discriminate and eliminate the potential interferences of intrinsic indicator compounds. Owing to the integration of sampling, extraction, injection, and decomposition into one step by SPME, the proposed method demonstrates exceptional sensitivity, eliminating the necessity for complex sample pretreatment procedures and the use of organic solvents. Finally, the proposed method was successfully applied in the determination of PMMA and PVDC MNPs in real aqueous samples.

Chemical and Electrophysiological Characterisation of Headspace Volatiles from Yeasts Attractive to Drosophila suzukii.

Chemical control of Drosophila suzukii (Diptera: Drosophilidae) based on the use of insecticides is particularly challenging as the insect attacks ripening fruits shortly before harvest. An alternative strategy may rely on the use of yeasts as phagostimulants and baits, applied on canopy as attract-and-kill formulations. The aim of this research was to identify the most attractive among six yeast species for D. suzukii: Saccharomyces cerevisiae, Hanseniaspora uvarum, Clavispora santaluciae, Saccharomycopsis vini, Issatchenkia terricola, and Metschnikowia pulcherrima. The volatile profile of C. santaluciae was described for the first time. Behavioural experiments identified H. uvarum and S. vini as the most attractive yeasts. The characterization of yeast headspace volatiles using direct headspace (DHS) and solid-phase microextraction (SPME) revealed several strain-specific compounds. With DHS injection, 19 volatiles were characterised, while SPME revealed 71 compounds constituting the yeast headspace. Both analyses revealed terpenoids including β-ocimene, citronellol, (Z)-geraniol (nerol), and geranial as distinct constituents of S. vini. H. uvarum and S. vini were further investigated using closed-loop stripping analysis (CSLA) and electroantennography. Out of 14 compounds quantified by CSLA, ethyl acetate, isoamyl acetate, β-myrcene, benzaldehyde and linalool were detected by D. suzukii antennae and might generate the strong attractiveness of S. vini and H. uvarum. Our results highlight a strong attraction of D. suzukii to various yeasts associated with both the flies and their habitat and demonstrate how different sampling methods can impact the results of volatile compound characterization. It remains to be demonstrated whether the distinct attraction is based on special adaptations to certain yeasts and to what extent the metabolites causing attraction are interchangeable.

Application of numerical simulation to solid phase-microextraction for decreasing of extraction time of pyrene and phthalate esters on solid coatings

Reynolds-Averaged Navier-Stokes (RANS) approach with the k-ε closure model is employed for the first time to simulate direct Solid-Phase Micro-Extraction (SPME) computationally. Simulations are performed by using COMSOL Multiphysics in order to examine methods to decrease the extraction time. Experiments are also conducted to support data obtained from the numerical framework. Di-n-Butyl Phthalate (DNBP) and etched steel wire are chosen as the analyte and the adsorbent, respectively. Stirring rate, fiber's location, stirrer magnet's size, and the method of sample rotation are examined to decrease the extraction time. In addition, the effects of adding a baffle to the vial and implementing a periodic function for stirring the sample are studied. Increasing the stirring rate from 700 to 3000 rpm reduces the extraction time from 50 to 36 minutes. Present results suggest that changing the fiber's location and implementing a periodic stirring pattern significantly decrease the extraction time of SPME. The optimum fiber's location is found at 7.5 mm far from the vial's center, which leads to a 51% decrease in the extraction time. Furthermore, using a periodic stirring pattern results in a 60% decrease in the extraction time compared to the traditional uniform stirring pattern. To examine the robustness and reliability of the presented framework, two additional analytes, namely pyrene and Dioctyl phthalate (DOP), are chosen with one additional fiber, Al2O3. In this regard, the additional materials are used in the framework to investigate the effects of fiber's location and stirring pattern. By optimizing the fiber's location, the extraction time is reduced by 36% and 40% for SPME of pyrene and DOP, respectively. On the other hand, by using a periodic stirring pattern, the extraction time is reduced by 42% and 46% for SPME of pyrene and DOP, respectively.

Cuticular Hydrocarbons of Anastrepha obliqua (Diptera: Tephritidae) as Influenced by Extraction Method, Natal Host, and Age

The primary function of cuticular hydrocarbons is to keep insects from losing water. However, cuticular hydrocarbons also may mediate chemical communication in a number of species. In this study, we investigated the effect of the extraction method, natal host, and age (maturation) on the cuticular hydrocarbon profiles of the West Indian fruit fly, Anastrepha obliqua (Macquart) (Diptera: Tephritidae). Cuticular hydrocarbons from female and male adults of different natal hosts (Mangifera indica L. or Spondias mombin L. [both Anacardiaceae]) and age were extracted by solvent extraction and direct contact solid-phase microextraction. Cuticular hydrocarbons were identified by gas chromatography coupled to mass spectrometry. In total, we recorded 12 compounds, but only 9 of them were identified. The identified cuticular hydrocarbons were linear alkanes (n-heneicosane, n-nonacosane, and n-hentriacontane), alkenes (n-heneicosene, n-tricosene, n-nonacosene, and n-hentriacontene), and branched alkanes (2-methyl-octacosane and 2-methyl-triacontane). There were no qualitative differences between sampling techniques. The solvent extraction method extracted more cuticular hydrocarbons from flies reared on mango compared to those extracted from flies reared on hog plum. In contrast, solid-phase microextraction extracted a higher concentration of cuticular hydrocarbons from flies reared on hog plum than to those extracted from flies reared on mango. Higher levels of 2-methyl-octacosane and 2-methyl-triacontane were detected with solvent extraction than with solid-phase microextraction; the opposite occurred with hentriacontane and unknown compound 2. The compounds n-heneicosene, n-heneicosane, and n-tricosene were present in mature males but not in mature females; n-nonacosene was found only in the mature flies of both sexes.

Crystal violet-modified HKUST-1 framework with improved hydrostability as an efficient adsorbent for direct solid-phase microextraction.

Metal-organic frameworks (MOFs) have received extensive attention in adsorption applications owing to their high surface area. However, some MOFs do not perform well as the extraction medium when used under aqueous conditions. The low hydrostability of MOFs limits the practical application of these materials in solid-phase microextraction (SPME). Here, the fabrication of a water resistance SPME fiber coating is introduced based on the crystal violet (CV)-modified HKUST-1 framework on copper (Cu@HKUST-1@CV). The HKUST-1 was prepared by the in situ growth method, followed by post-synthetic modification of HKUST-1 with the CV layer. The preparation of the modified HKUST-1 was characterized by FESEM, XRD, FTIR, and DFT approaches. The prepared SPME coating was successfully employed for the quantification of anthracene (AN), as a model analyte, in water samples. The limit of detection was 0.8 ng mL-1. The developed method will open up a new door towards searching for promising materials in SPME applications.

In-site and solvent-free exfoliation of porous graphene oxide from pencil lead fiber for solid-phase microextraction of cadmium ion before GF-AAS determination.

Graphene oxide (GO)-functionalized pencil lead fiber was prepared for the first timeby in situ oxidation and exfoliation of graphite contained in pencil lead fiber to porous graphene oxide structure via a one-step solvent-free dielectric barrier discharge (DBD) microplasma treatment. This new fiber was demonstrated as a highly efficient and low-cost solid-phase microextraction (SPME) fiber for the determination of toxic metal ions. The fiber extraction performance was evaluated by using cadmium as a model analyte in a direct immersing SPME mode. Unlike mostcommercially available and other lab-built fibers, the preparation of the graphene oxidized pencil lead fiber is environmentally friendly, low cost, and non-toxic without using any organic solvents. The fiber is robust due to its coating-free configuration. Furthermore, high extraction efficiency and high sensitivity for cadmium can be obtained due to the abundant oxygen-containing functional groups on the surface of the novel fiber. After extraction, the cadmium adsorbed on the fiber was desorbed to 150-μL solution. Graphite furnace atomic absorption spectrometry (GF-AAS) with low sample consumption was used to determine cadmium. The calibration curve for cadmium ions was linear in a range 0.04-0.26μgL-1 with a detection limit of 0.005μgL-1. A relative standard deviation (RSD, n = 5) of 2.1% was obtained at 0.1μgL-1 of cadmium. The sensitivity enhancement factor (EF) value of the proposed SPME method was 25. The SPME fiber was successfully applied to determinecadmium in tap water, river water, and pond water with spike recoveries ranging from 94 to 105%. Pipe network water samples were also analyzed to evaluate the cadmium release to drinking water due to the corrosion of tubes.

A Comparison of Collection Methods for Microbial Volatiles

Recently, there has been an increase in the number of reports that highlight the role of microbes and their volatile metabolites in interactions with plants and insects, including interactions which may benefit agricultural production. Accurate and reproducible volatile collection is crucial to investigations of chemical-mediated communication between organisms. Accordingly, accurate detection of volatiles emitted from microbe-inoculated media is a research priority. Though numerous classes of volatile organic compounds are emitted from plants, insects, and microbes, emissions from microbes typically contain polar compounds of high volatility. Therefore, commonly used plant or insect volatile collection techniques may not provide an accurate representation of microbe-specific volatile profiles. Here, we present and compare the volatile data derived via three solventless collection techniques: direct headspace injection, solid-phase microextraction (SPME), and active sampling with a sorptive matrix blend specifically designed to prevent collection filter breakthrough of VOCs (solid-phase extraction, SPE). These methods were applied to a synthetic floral nectar media containing a nectar-inhabiting yeast, Metschnikowia reukaufii, and sunflower (Helianthus annus) pollen. The yeast contributed alcohols, ketones, and esters, and the pollen provided terpenoids. Direct headspace injections were not effective, and the resultant chromatography was poor despite the use of on-column cryofocusing. SPME and SPE detected a similar number of volatiles, but with varying relative abundances. SPE collected a greater abundance of microbial volatiles than SPME, a difference driven by high ethanol capture in SPE. Both SPE and SPME are appropriate for analysis of microbial volatiles, though the sorbent type and amount, and other collection parameters should be further evaluated for each studied system.

Rapid screening and quantitation of PAHs in water and complex sample matrices by solid-phase microextraction coupled to capillary atmospheric pressure photoionization-mass spectrometry.

A capillary atmospheric pressure photoionization (cAPPI) source was used to analyze polycyclic aromatic hydrocarbons (PAHs) in complex matrices like grilled meat extract and urban dust reference material, as well as screening for PAHs in aqueous samples such as tap and lake water. A high-throughput workflow was developed that allowed rapid screening of unknown samples by direct solid-phase microextraction (SPME) coupled with cAPPI-MS, with confirmatory gas chromatography performed only for samples containing trace amounts of PAHs. Extraction times were as low as 15 s, with a total analysis time of 2 min per sample for screening. Limits of detections were in the low pg/ml range and in the subpg/ml range for the direct and chromatographic approach, respectively, with a linear dynamic range between two and three orders of magnitude, as determined for 15 model PAHs. This rapid approach represents an attractive way to screen samples containing nonpolar compounds using an ambient ionization source.

Rapid and accurate determination of trace volatile sulfur compounds in human halitosis by an adaptable active sampling system coupling with gas chromatography.

Halitosis with the main components of trace volatile sulfur compounds widely affects the quality of life. In this study, an adaptable active sampling system with two sample-collection modes of direct injection and solid-phase microextraction was developed for the rapid and precise determination of trace volatile sulfur compounds in human halitosis coupled with gas chromatography-flame photometric detection. The active sampling system was well designed and produced for efficiently sampling and precisely determining trace volatile targets in halitosis under the optimized sampling and detection conditions. The analytical method established was successfully applied for the determination of trace targets in halitosis. The limits of detection of H2 S, CH3 SH, and CH3 SCH3 by direct injection were 0.0140-23.0μg/L with good recoveries ranging from 82.2 to 118% and satisfactory relative standard deviations of 0.4-9.5% (n=3), respectively. The limit of detections of CH3 SH and CH3 SCH3 by solid-phase microextraction were 2.03 and 0.186 × 10-3 μg/L with good recoveries ranging from 98.3 to 108% and relative standard deviations of 5.9-9.0% (n=3). Trace volatile targets in positive real samples could be actually found and quantified by combination of direct injection and solid-phase microextraction. This method was reliable and efficient for the determination of trace volatile sulfur compounds in halitosis.

Effects of Different Steeping Temperatures on the Leaching of Aroma Components in Black Tea by SPME–GC–MS Coupled with Chemometric Method

Abstract Background: Black tea is famous for its unique aroma. The analysis of aroma components has attracted considerable attention worldwide because of its complex chemical composition and low concentration. Objective: Steeping temperature is one of the most important factors affecting the aroma of black tea. This study aims to evaluate the effects of four steeping temperatures [60, 70, 80, and 95°C (boiling water)]. Methods: Two major factors affecting extraction performance, including the type of extraction method [direct headspace injection (HS) and solid-phase microextraction (SPME)] and extraction time (50, 60, and 70 min), were optimized to enrich and analyze the aroma components of Congou black tea by GC–MS. In addition, heuristic evolving latent projection (HELP), an effective chemometric resolution method, was employed to resolve the overlapped peaks. Results: A total of 83 aroma components were tentatively identified by GC–MS, such as alcohol (42.06–50.52%), aldehyde (12.09–15.97%), and hydrocarbon (4.79–15.32%). Linalool and its oxides (25.49–36.24%) were the most abundant aroma components, followed by geraniol (2.55–8.54%), methyl salicylate (1.84–9.50%), and nerol (1.93–4.41%). Conclusions: The black tea steeped at 95°C smelled more pleasant with mild green, roast, and fruity aroma. Moreover, at 80°C, the tea had sweeter fragrance with floral aroma, while steeping at 60 and 70°C resulted in more reinforced woody and fatty aroma. Highlights: A total of 83 aroma components of black tea were tentatively identified by SPME–GC–MS. The overlapped peaks were resolved by the HELP method. Aroma characteristics of different steeping temperatures were revealed.

Preparation of polypyrrole/nanosilica composite for solid-phase microextraction of bisphenol and phthalates migrated from containers to eye drops and injection solutions

This paper describes the electrodeposition of polyphosphate-doped polypyrrole/nanosilica nanocomposite coating on steel wire for direct solid-phase microextraction of bisphenol A and five phthalates. We optimized influencing parameters on the extraction efficiency and morphology of the nanocomposite such as deposition potential, concentration of pyrrole and polyphosphate, deposition time and the nanosilica amount. Under the optimized conditions, characterization of the nanocomposite was investigated by scanning electron microscopy and Fourier transform infra-red spectroscopy. Also, the factors related to the solid-phase microextraction method including desorption temperature and time, extraction temperature and time, ionic strength and pH were studied in detail. Subsequently, the proposed method was validated by gas chromatography-mass spectrometry by thermal desorption and acceptable figures of merit were obtained. The linearity of the calibration curves was between 0.01 and 50 ng/mL with acceptable correlation coefficients (0.9956–0.9987) and limits of detection were in the range 0.002–0.01 ng/mL. Relative standard deviations in terms of intra-day and inter-day by five replicate analyses from aqueous solutions containing 0.1 ng/mL of target analytes were in the range 3.3%–5.4% and 5%–7.1%, respectively. Fiber-to-fiber reproducibilities were measured for three different fibers prepared in the same conditions and the results were between 7.3% and 9.8%. Also, extraction recoveries at two different concentrations were ≥96%. Finally, the suitability of the proposed method was demonstrated through its application to the analysis of some eye drops and injection solutions.

Effects of Different Steeping Temperatures on the Leaching of Aroma Components in Black Tea by SPME-GC-MS Coupled with Chemometric Method.

Background: Black tea is famous for its unique aroma. The analysis of aroma components has attracted considerable attention worldwide because of its complex chemical composition and low concentration. Objective: Steeping temperature is one of the most important factors affecting the aroma of black tea. This study aims to evaluate the effects of four steeping temperatures [60, 70, 80, and 95°C (boiling water)]. Methods: Two major factors affecting extraction performance, including the type of extraction method [direct headspace injection (HS) and solid-phase microextraction (SPME)] and extraction time (50, 60, and 70 min), were optimized to enrich and analyze the aroma components of Congou black tea by GC-MS. In addition, heuristic evolving latent projection (HELP), an effective chemometric resolution method, was employed to resolve the overlapped peaks. Results: A total of 83 aroma components were tentatively identified by GC-MS, such as alcohol (42.06-50.52%), aldehyde (12.09-15.97%), and hydrocarbon (4.79-15.32%). Linalool and its oxides (25.49-36.24%) were the most abundant aroma components, followed by geraniol (2.55-8.54%), methyl salicylate (1.84-9.50%), and nerol (1.93-4.41%). Conclusions: The black tea steeped at 95°C smelled more pleasant with mild green, roast, and fruity aroma. Moreover, at 80°C, the tea had sweeter fragrance with floral aroma, while steeping at 60 and 70°C resulted in more reinforced woody and fatty aroma. Highlights: A total of 83 aroma components of black tea were tentatively identified by SPME-GC-MS. The overlapped peaks were resolved by the HELP method. Aroma characteristics of different steeping temperatures were revealed.

A new restricted access molecularly imprinted fiber for direct solid phase microextraction of benzodiazepines from plasma samples.

Restricted access molecularly imprinted polymers (RAMIPs) are hybrid materials that present selective binding sites for a template (or similar molecules), and an external hydrophilic layer that avoids the binding of proteins to the material, making them appropriate for the sample preparation of protein fluids. RAMIPs have been used successfully in online and offline solid phase extractions, but there is no application as a fiber in solid phase microextraction (SPME), to the best of our knowledge. In this paper, molecularly imprinted fibers were synthesized inside glass capillary tubes (0.53 mm i.d.), using diazepam and methacrylic acid as template and functional monomer, respectively. The MIP fibers were coated with a cross-linked bovine serum albumin (BSA) layer, resulting in RAMIP fibers that were used in the SPME of benzodiazepines directly from biological fluids. The BSA layer acts as a protective barrier that avoids the binding of proteins from the sample by an electrostatic repulsion mechanism. The protein exclusion capacity of the RAMIP fiber was about 98%, which is selective to benzodiazepines in comparison with other drugs (citalopram and fluoxetine). The SPME was optimized and the extraction conditions were set as follows: 1000 μL of the sample diluted with water (1 : 0.5, v : v), no pH adjustment, an extraction time of 20 min at 500 rpm, and elution with 200 μL of acetonitrile for 5 min at 500 rpm. The fibers were used in the SPME of benzodiazepines directly from plasma samples, followed by HPLC-DAD analyses. The method was linear for bromazepam (50-750 μg L-1), clonazepam (15-250 μg L-1), alprazolam (15-350 μg L-1), nordiazepam (100-2100 μg L-1) and diazepam (100-2600 μg L-1), with correlation coefficients higher than 0.97. Relative standard deviations (precision) and relative errors (accuracy) ranged from 0.5 to 20.0%, and -15.6 to 21.6%, respectively.

Characterization of Plant Volatiles Reveals Distinct Metabolic Profiles and Pathways among 12 Brassicaceae Vegetables.

Plants emit characteristic organic volatile compounds (VOCs) with diverse biological/ecological functions. However, the links between plant species/varieties and their phytochemical emission profiles remain elusive. Here, we developed a direct headspace solid-phase microextraction (HS-SPME) technique and combined with non-targeted gas chromatography‒high-resolution mass spectrometry (GC-HRMS) platform to investigate the VOCs profiles of 12 common Brassicaceae vegetables (watercress, rocket, Brussels sprouts, broccoli, kai lan, choy sum, pak choi, cabbage, Chinese cabbage, cauliflower, radish and cherry radish). The direct HS-SPME sampling approach enabled reproducible capture of the rapid-emitting VOCs upon plant tissue disruption. The results revealed extensive variation in VOCs profiles among the 12 Brassicaceae vegetables. Furthermore, principal component analysis (PCA) showed that the VOC profiles could clearly distinguish the 12 Brassicaceae vegetables, and that these profiles well reflected the classical morphological classification. After multivariate statistical analysis, 44 VOCs with significant differences among the Brassicaceae vegetables were identified. Pathway analysis showed that three secondary metabolism pathways, including the fatty acid pathway, methylerythritol phosphate (MEP) pathway and glucosinolate (GLS) pathway, behave distinctively in these vegetables. These three pathways are responsible for the generation and emission of green leaf volatiles (GLVs), terpenes and isothiocyanates (ITCs), respectively. Correlation analysis further showed that volatile metabolites formed via the common pathway had significantly positive correlations, whereas metabolites from different pathways had either non-significant or significantly negative correlations. Genetic influences on these metabolites across various vegetable types were also evaluated. These findings extend our phytochemical knowledge of the 12 edible Brassicaceae vegetables and provide useful information on their secondary metabolism.

High-throughput screening of PAHs and polar trace contaminants in water matrices by direct solid-phase microextraction coupled to a dielectric barrier discharge ionization source

Ambient mass spectrometry enables fast and direct analysis, requiring minimal or no sample preparation; these attributes have established it as the preferred technique for applications in numerous fields (e.g., biomedical, forensic, and environmental). Here we coupled an active capillary plasma ionization source based on a dielectric barrier discharge directly to solid-phase microextraction, achieving a quick (<10 min per sample), green (virtually no samples preparation and thus no solvents involved), sensitive (LODs up to 3 pg mL−1), robust (RSD of <20%), and quantitative (LDR ≥ 2 orders of magnitude) screening method. This study, moreover, shows that intrinsically poorer ionization efficiencies for low-polarity compounds (such as polycyclic aromatic hydrocarbons, PAHs), which precluded their ultra-trace detection, can be partially overcome by adding dopants and lowering the LODs into the pg mL−1 range. Results also show that the presence of these dopants greatly affects the ionization mechanism, resulting in the preferential formation of radical cations versus protonated PAHs. As a proof of concept, this method was applied to the detection of organic microcontaminants in different water matrices (such as tap, ground, and treated wastewater). Common contaminants (e.g., DEET, benzotriazole, β-estradiol) were tentatively detected and, if above the LOQ, quantified (i.e., DEET at 30 pg mL−1). These promising results evidence that this approach is interesting for quick (field) screening methods, and the newly increased efficiency for a larger polarity range additionally expands the range of possible applications.

Direct solid phase microextraction combined with gas chromatography – Mass spectrometry for the determination of biogenic amines in wine

A direct method based on immersion solid phase microextraction (DI-SPME) gas chromatography mass-spectrometry (GC-MS) was optimized and validated for the determination of 16 biogenic amines in Polish wines. In the analysis two internal standards were used: 1,7-diaminoheptane and bis-3-aminopropylamine. The method allows for simultaneous extraction and derivatization, providing a simple and fast mode of extraction and enrichment. Different parameters which affect the extraction procedure were studied and optimized including ionic strength (0–25%), fiber materials (PDMS/DVB, PDMS/DVD + OC, Polyacrylate, Carboxen/PDMS and DVB/CAR/PDMS) and timings of the extraction, derivatization and desorption processes. Validation studies confirmed the linearity, sensitivity, precision and accuracy of the method. The method was successfully applied to the analysis of 44 wine samples originating from several regions of Poland and 3 wine samples from other countries. Analysis showed that many of the samples contained all examined biogenic amines. The method, assessed using an Eco-Scale tool with satisfactory results, was found to be green in terms of hazardous chemicals and solvents usage, energy consumption and production of waste. Therefore the proposed method can be safely used in the wine industry for routine analysis of BAs in wine samples with a minimal detrimental impact on human health and the environment.

Application of Amine and Phosphotungstic Acid Groups as a Novel Bifunctional Fiber Coating in SPME-HPLC of Volatile Phenols in Water

The utilization of a bifunctional amine and H3PW12O40 (PW12) as a direct solid-phase microextraction (D-SPME) coating was investigated for the first time. The fiber was synthesized using positively charged 3-aminopropyltriethoxysilane as the crosslinking agent, and provided sites for the immobilization of PW12. Fourier transform infrared spectroscopy and field emission scanning electron microscopy were used to characterize the synthetic compound. This new fiber was developed to determine some chlorophenols [4-chlorophenol (4-CPh), 2,3-dichlorophenol (2,3-DCPh), and 2,4,6-trichlorophenol (2,4,6-TCPh)] via SPME-HPLC. Using the experimental design method, the adsorption and desorption factors of the fiber—including ionic strength and adsorption and desorption times—for the three chlorophenols were systematically investigated by SPME-HPLC-UV. In the concentration range 50–5000 µg L−1, the calibration curves were linear for the analytes and the limits of detection varied from 0.3 to 2.5 µg L−1. The single-fiber repeatability and fiber-to-fiber reproducibility were in the ranges 4.8–6.4 and 10.2–12.1%, respectively. The application of the fiber to environmental water samples spiked at 70 µg L−1 with the chlorophenols yielded recoveries in the range 88.80–92.88%. Advantages of this novel bifunctional-coated SPME fiber include its increased extraction efficiency for chlorophenols and its long lifetime (it was used for >70 cycles of D-SPME-HPLC operation without showing any appreciable reduction in extraction performance).

Fabrication of Metal-Organic Framework MOF-177 Coatings on Stainless Steel Fibers for Head-Space Solid-Phase Microextraction of Phenols.

Direct head-space solid-phase microextraction (HS-SPME) of phenols in water is usually difficult due to its polarity and solubility in aqueous matrix. Herein we report the fabrication of metal-organic framework MOF-177 coated stainless steel fiber for the HS-SPME of phenols (2-methylolphenol, 4-methylolphenol, 2,4-dimethylolphenol, 2,4-dichlorphenol, and 3-methyl-4-chlorophenol) in environmental water samples prior to the gas chromatography-mass spectrometry detection. Several parameters affecting the extraction efficiency were optimized in the experiment, including extraction temperature and time, the pH value and salt addition. The results indicated that the coated fiber gave low detection limits (0.015-0.043μg L-1) and good repeatability with the RSD ranging from 2.8% to 5.5% for phenols. The recoveries are between 84.5%-98.6% with the spiked level of 10μg L-1 for the real water samples. The established method may afford a kind of potential enrichment material and a reference method for the analysis of methylphenols in water samples.

Determining the permeability of organic solvents through PVC pipes using a direct SPME model

The permeability of aromatic hydrocarbons, i.e. BTEX and styrene, through PVC pipes was investigated using a 6-cm pipe-bottle model with direct solid-phase microextraction (SPME) sampling. It was found that an aromatic hydrocarbon with a large molecular size or low polarity may be less permeable through PVC pipes. In addition, the diffusion coefficients of BTEX and styrene in PVC pipes ranged from 4.87 to 7.64 × 10−8 cm2/s. According to the simulation results of a one-dimensional diffusion model, it is speculated that diffusion transport of benzene and toluene in PVC pipes may have non-Fickian behavior. The advantage of using the innovated test model is that SPME provides a nondestructive analytical means to monitor the concentrations of organic compounds in pipe-water. Therefore, the pipe-bottle model developed herein has potential applications in determining the resistance of polymeric pipes to permeation by solvents in the aqueous solution.