Microextraction Device Research Articles

Development of a Hydrophilic Lipophilic Balanced Thin Film Solid Phase Microextraction Device for Balanced Determination of Volatile Organic Compounds.

A novel hydrophilic-lipophilic balanced (HLB) thin film solid-phase microextraction (TF-SPME) device is proposed for polarity-balanced determinations of volatile organic compounds. The proposed HLB particles used in the preparation of these membranes were prepared using a precipitation polymerization technique and determined to have a specific surface area of 335 m2/g with an average pore diameter of 13 Å. Membranes prepared from these particles were found to extract 1.8, 2.2, 1.9, 1.7, 2.0, and 1.3 times more benzene, 2-pentanone, 1-nitropropane, pyridine, 1-pentanol, and octane, respectively, than the established divinylbenzene/polydimethylsiloxane (DVB/PDMS)-based membranes. Furthermore, membranes prepared from these lab-made particles were shown to extract significantly ( p = 0.00047) larger amounts of these analytes than membranes prepared from comparative commercial HLB particles. The intermembrane extraction efficiency between 3 membranes was determined to be reproducible at 95% confidence for 4 different coating chemistries tested, including the DVB/PDMS membranes, and those prepared with 3 different HLB compositions. Furthermore, method reliability was established by confirming that, once extracted, modified McReynolds standards were stable on the HLB/PDMS membranes stored in thermal desorption tubes on an autosampler rack for at least 120 h, for 5 of the 6 standards, but only for 24 h for pyridine at a 95% level of confidence. Finally, using a TF-SPME enabled, portable GC/MS instrument, an entirely on-site proof of concept application was performed for the determination and quantitation of chlorination byproducts in a private hot tub, successfully identifying chloroform, bromodichloromethane, dichloroacetonitrile, chlorobenzene, benzonitrile, and benzyl chloride, while further quantifying chloroform and dichloroacetonitrile at levels of 270 and 79 ppb with %RSD values of 13% and 5%, respectively.

Development and validation of eco-friendly strategies based on thin film microextraction for water analysis

The aim of the current study is the establishment of Green Analytical Chemistry strategies for water analysis by elimination/reduction of hazardous chemicals, energy consumption, and waste generation throughout the entire analytical workflow. The first approach introduced in this manuscript consists of addition of water to a sampling vessel that contains a thin film microextraction (TFME) device, followed by removal of the device after equilibration, and subsequent quantification of the extracted components by thermal desorption GC/MS. In this approach, namely the in-bottle TFME approach, analyte-loss associated errors that stem from analyte adherence to glass surfaces and/or degradation are avoided as extraction occurs in situ, while analytes are isolated from a complex matrix that contains degradation agents (bacteria, oxidizing or reducing species, etc.). This procedure also circumvents the splitting of original samples into sub-samples. The second approach involves the use of portable TFME devices that facilitate on-site extraction of compounds, therefore eliminating the use of collection vessels, a factor known to potentially introduce errors into analysis. The herein described procedure involves attachment of the TFME device to drill accessories, analyte extraction via direct immersion into sampled site, and subsequent on-site instrumental analysis, which is carried out with the use of a portable GC/MS containing an appropriate thermal desorption interface, or alternatively, by transferring the membrane to the laboratory for bench-top GC/MS analysis. To facilitate a better understanding of the processes governing the developed approaches, modeling by COMSOL Multiphysics® software was performed. The findings of this study were applied for further method optimization, and the optimized developed methods were then applied for on-site surface water analyses. Finally, the greenness of the developed methods was evaluated with use of the eco-scale assessment, with obtained scores compared to that of the US EPA 8270 method.

Developing a new sensitive solid-phase microextraction fiber based on carbon nanotubes for preconcentration of morphine

The ability of extraction and preconcentration of small amounts of substances from biological samples is important in forensic medicine. In the present study, we produced a new solid-phase microextraction fiber based on carbon nanotube (CNTs) for extraction and preconcentration of small amount of morphine in urine sample. Raw nanofibers were first carboxylated with H2SO4/HNO3 (3:1) and then functionalized with ethylenediamine. Functionalization was confirmed by FTIR and Raman spectroscopy as well as SEM analysis. The functionalized CNTs were coated on a porous polypropylene hollow fiber. A new electrical device was designed and manufactured for adsorption–desorption of the analyte, in which the voltage could be reversed and the analytes could desorb into the washing solution for HPLC analysis. The results showed that the prepared fiber could adsorb a very low concentration of morphine (0.5 ppb) in urine matrix, and was successfully used for up to 50 times with no significant loss in the extraction efficiency. Recovery of the fiber was 77% at 0.5 ppb. The optimum condition for the fiber was 2 min at 1 V of the manufactured electrical catalyst controller. This fiber can be used for the detection of a small amount of morphine in biological samples, which are not detectable by conventional methods. Simple mechanism of this fiber in preconcentrating morphine makes it a novel candidate for detection of other opiates and drugs of abuses in crime scene investigations and postmortem examinations several days after exposure. The prepared electric microextraction device could also efficiently concentrate the morphine in the urine matrix.

Fabric Phase Sorptive Extraction: Current State of the Art and Future Perspectives

Fabric phase sorptive extraction (FPSE) is a novel and green sample preparation technique introduced in 2014. FPSE utilizes a natural or synthetic permeable and flexible fabric substrate chemically coated with a sol-gel organic-inorganic hybrid sorbent in the form of ultra-thin coating, which leads to a fast and sensitive micro-extraction device. The flexible FPSE requires no modification of samples and allows direct extraction of analytes. Sol-gel sorbent-coated FPSE media possesses high chemical, solvent, and thermal stability due to the strong covalent bonding between the substrate and the sol-gel sorbent. Therefore, any elution solvent can be used in a small volume, which achieves a high pre-concentration factor without requiring any solvent evaporation and sample reconstitution step. Taking into consideration the complexity of the samples and the need of further minimization and automation, some new, alternative modes of the FPSE have also been developed. Therefore, FPSE has attracted the interest of the scientific community that deals with sample pre-treatment and has been successfully applied for the extraction and determination of many analytes in environmental samples as well as in food and biological samples. The objective of the current review is to present and classify the applications of FPSE according to different sample categories and to briefly show the progress, advantages, and the main principles of the proposed technique.

Application of micro-solid-phase extraction for determination of released dental fillings components in artificial saliva solution

In this work, the microextraction devices in form of sachets were prepared and used for isolation of released dental fillings components from artificial saliva solutions As sorbents mesoporous aluminosilicate and C18-bonded silica were used. Gas chromatography was used for indication of analytes in samples. The dependence of adsorption on variable factors were determined. The effect of adsorbent mass, the membrane type for μ-SPE device and time of adsorption on the efficiency of the process were examined. The dependence between the extraction recovery and the desorption solvent was also indicated. Based on calculated adsorption capacities in time of adsorption and equilibrium state the kinetic study was prepared. The validation of determination method by using of membrane-protected microextraction for sample preparation was conducted. The developed method proved to be convenient and offers good reproducibility. The detection limits of the method under optimized conditions were in the range of 0,117 μg mL−1 for camphor to 1407 μg mL−1 for 4-methoxyphenol. Two examined membrane protected sorbent were successfully applied for extraction of eluted dental ingredients.

Efficient and Versatile Pipet Microextraction Device Based on a Light-Heatable Sorbent.

Miniaturized sample pretreatment platforms have simplified analytical tasks in diverse disciplines. Herein, a novel pipet microextraction (PME) device is reported by making use of the photothermal property of a light-heatable sorbent (LHS) for the first time. Efficient and staining-free heating treatment of small volumes of liquids confined in the PME device is now enabled through light illumination. The light-induced heating treatment is capable of dramatically accelerating solvent elution rates, effectively unlocking bound toxin from its antibody, and rapidly quenching enzymatic activities, thus, providesPME with higher efficiencies and enables its new applications in antibody-intermediated sampling of targeted toxin from stained food surfaces and powders, as well as in accurate revelation of enzymatic reaction kinetics. This study offers a new perspective of designing efficient and versatile microextraction platforms and demonstrates their potential applications in different fields including public security, new drug development, and environmental protection.

Polymeric ionic liquid-based portable tip microextraction device for on-site sample preparation of water samples

On-site sample preparation is highly desired because it avoids the transportation of large-volume samples and ensures the accuracy of the analytical results. In this work, a portable prototype of tip microextraction device (TMD) was designed and developed for on-site sample pretreatment. The assembly procedure of TMD is quite simple. Firstly, polymeric ionic liquid (PIL)-based adsorbent was in-situ prepared in a pipette tip. After that, the tip was connected with a syringe which was driven by a bidirectional motor. The flow rates in adsorption and desorption steps were controlled accurately by the motor. To evaluate the practicability of the developed device, the TMD was used to on-site sample preparation of waters and combined with high-performance liquid chromatography with diode array detection to measure trace estrogens in water samples. Under the most favorable conditions, the limits of detection (LODs, S/N = 3) for the target analytes were in the range of 4.9–22 ng/L, with good coefficients of determination. Confirmatory study well evidences that the extraction performance of TMD is comparable to that of the traditional laboratory solid-phase extraction process, but the proposed TMD is more simple and convenient. At the same time, the TMD avoids complicated sampling and transferring steps of large-volume water samples.

In-needle Microextraction Coupled with Gas Chromatography/Mass Spectrometry for the Analysis of Phthalates Generating from Food Containers

In this study, we fabricated a new device for headspace in-needle microextraction using a stainless steel wire coated with multiwalled carbon nanotube/polyaniline composite by coulometric technique. Then, the coated wire was placed into a stainless steel needle inside. This headspace in-needle microextraction device was applied for the determination of phthalates dissolved in aqueous solution by gas chromatography-mass spectrometry. Multiwalled carbon nanotube/polyaniline composite film of 10 mm length on the surface of stainless steel wire was optimized to polymerize electrochemically when constant potential of 2.0 V was applied during 500 s. Atomic force microscopy and Auger electron spectroscopy showed that polymerization on the surface of wire had smooth, homogeneous, and constant coating thickness of 1.5 ± 0.004 μm. The optimum molar ratio of multiwalled carbon nanotube and aniline (C:N) for polymerization was determined at 1: 2 M ratio. The optimum conditions of the proposed method were extraction temperature 50 °C, saturation time 60 min, extraction time 30 min, desorption temperature 230 °C, and desorption time 3 min, respectively. Validation of headspace in-needle microextraction-multiwalled carbon nanotube/polyaniline coupled with GC/MS was also performed including limit of detection, limit of quantitation, dynamic range, recovery, and reproducibility. The proposed device is found to be inexpensive, easy, and rapid to fabricate and could be utilized effectively as the solventless microextraction method for the analysis of phthalates generating from food containers.

Fiber-in-tube solid-phase microextraction of caffeine as a molecular tracer in wastewater by electrochemically deposited layered double hydroxide.

Modified stainless-steel wires with a layer of polyaniline conductive polymer were coated by electrochemical deposition with Zn/Al layered double hydroxide to make solid-phase microextraction fibers. The coating layer was also electrochemically deposited on the inner surface of a stainless-steel tube. Then, ten prepared fibers were put inside the inner coated tube to make a fiber-in-tube solid phase microextraction device. The device was applied for the extraction of caffeine (1,3,7-trimethylxanthine) from domestic wastewater samples. Extraction conditions including extraction and desorption times, pH and ionic strength of the sample solution, and content of the organic desorption solvent were investigated and optimized. Under the optimized conditions, the fiber-in-tube solid phase microextraction exhibited excellent extraction efficiency toward caffeine. The precision of the method was evaluated. Average relative standard deviation of 5.7% (n=6) for intraday analysis and 8.3% (n=5) for interday analysis was obtained. The limits of detection and limits of quantification of the method (at signal to noise ratio of 3 and 10) were obtained as 0.14 and 0.37ng/mL, respectively. The current study can provide new prospective applications of layered double hydroxide conductive polymer fiber coatings.

New-generation bar adsorptive microextraction (BAμE) devices for a better eco-user-friendly analytical approach–Application for the determination of antidepressant pharmaceuticals in biological fluids

The present contribution aims to design new-generation bar adsorptive microextraction (BAμE) devices that promote an innovative and much better user-friendly analytical approach. The novel BAμE devices were lab-made prepared having smaller dimensions by using flexible nylon-based supports (7.5 × 1.0 mm) coated with convenient sorbents (≈ 0.5 mg). This novel advance allows effective microextraction and back-extraction (‘only single liquid desorption step’) stages as well as interfacing enhancement with the instrumental systems dedicated for routine analysis. To evaluate the achievements of these improvements, four antidepressant agents (bupropion, citalopram, amitriptyline and trazodone) were used as model compounds in aqueous media combined with liquid chromatography (LC) systems. By using an N-vinylpyrrolidone based-polymer phase good selectivity and efficiency were obtained. Assays performed on 25 mL spiked aqueous samples, yielded average recoveries in between 67.8 ± 12.4% (bupropion) and 88.3 ± 12.1% (citalopram), under optimized experimental conditions. The analytical performance also showed convenient precision (RSD < 12%) and detection limits (50 ng L−1), as well as linear dynamic ranges (160–2000 ng L−1) with suitable determination coefficients (r2 > 0.9820). The application of the proposed analytical approach on biological fluids showed negligible matrix effects by using the standard addition methodology. From the data obtained, the new-generation BAμE devices presented herein provide an innovative and robust analytical cycle, are simple to prepare, cost-effective, user-friendly and compatible with the current LC autosampler systems. Furthermore, the novel devices were designed to be disposable and used together with negligible amounts of organic solvents (100 μL) during back-extraction, in compliance with the green analytical chemistry principles. In short, the new-generation BAμE devices showed to be an eco-user-friendly approach for trace analysis of priority compounds in biological fluids and a versatile alternative over other well-stablished sorption-based microextraction techniques.

Development of a microextraction by packed sorbent with gas chromatography‐mass spectrometry method for quantification of nitroexplosives in aqueous and fluidic biological samples

A new method for quantification of 12 nitroaromatic compounds including 2,4,6-trinitrotoluene, its metabolites and 2,4,6-trinitrophenyl-N-methylnitramine with microextraction by packed sorbent followed by gas chromatography and mass spectrometric detection in environmental and biological samples is developed. The microextraction device employs 4mg of C18 silica sorbent inserted into a microvolume syringe for sample preparation. Several parameters capable of influencing the microextraction procedure, namely, number of extraction cycles, washing solvent, volume of washing solvent, elution solvent, volume of eluting solvent and pH of matrix, were optimized. The developed method produced satisfactory results with excellent values of coefficient of determination (R2 >0.9804) within the established calibration range. The extraction yields were satisfactory for all analytes (>89.32%) for aqueous samples and (>87.45%) for fluidic biological samples. The limits of detection values lie in the range 14-828pg/mL.

Basalt fibers functionalized with gold nanoparticles for in-tube solid-phase microextraction.

Basalt fibers were functionalized with gold nanoparticles and characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. An in-tube solid-phase microextraction device was developed by packing the functionalized basalt fibers in a polyether ether ketone tube. The device was connected into high performance liquid chromatography equipment with a diode array detector to build online enrichment and analysis system. Eight polycyclic aromatic hydrocarbons were used as model analytes, important factors including sampling rate, sampling volume, organic solvent content in sample, and desorption time were investigated. Linear range (0.01-20 μg/L), detection limits (0.003-0.015 μg/L), and enrichment factors (130-1628) were given by the online analysis method. Relative standard deviations (n=5) of extraction repeatability on one tube and tube-to-tube repeatability were less than 5.2 and 14.7%, respectively. The analysis method was applied to detect polycyclic aromatic hydrocarbons in environmental water samples, and relative recoveries ranged from 87 to 128%.

Evaluation of a cooling/heating-assisted microextraction instrument using a needle trap device packed with aminosilica/graphene oxide nanocomposites, covalently attached to cotton.

A low-cost and reliable cooling/heating-assisted microextraction (CHaME) instrument was designed and fabricated for use in different modes of microextraction methods. The CHaME setup is able to cool down the sorbent and simultaneously heat the sample in a wide temperature range. Consequently, it can create a large thermal gap between the sorbent and the sample matrix, to promote the release of analytes from the sample tissue and enhance their effective trapping on the microextraction phase. The primary versions of the instrument have previously been evaluated, coupled with different modes of solid- and liquid-phase microextraction strategies. Compared with conventional microextraction systems, it is able to extract volatile organic compounds from complicated solid matrices more effectively, rapidly and without any need for a sample preparation step. In this research, the final and compact version of the CHaME instrument was fabricated and employed in a cooling/heating-assisted needle trap device (CHaME-NTD) for microextraction of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil samples, prior to GC-FID determination. An aminosilica/graphene oxide nanocomposite was synthesized, covalently attached to cotton (Am-Si/GO/Cot), packed inside a needle, and applied as an effective sorbent for trapping of the analytes. The influence of experimental parameters on the extraction efficiency of the TC-NTD-GC-FID strategy was evaluated and optimized. Under the optimal conditions, linear dynamic ranges (LDRs), limits of detection (LODs), and relative standard deviations (RSDs) for the PAHs were 0.001-2.0 μg g-1, 5-38 pg g-1, and 6.2-9.8% (n = 6), respectively. The CHaME-NTD-GC-FID procedure was compared with the traditional NTD-GC-FID method. Additionally, the Am-Si/GO/Cot nanocomposite sorbent was compared with the most frequently used commercial sorbents. The results demonstrated the remarkable performance of the CHaME-NTD procedure and the Am-Si/GO/Cot composite sorbent. The developed setup was also used for the extraction and determination of PAHs in contaminated soil samples, through the CHaME-NTD-GC-FID procedure.

Novel Electrosorption-Enhanced Solid-Phase Microextraction Device for Ultrafast In Vivo Sampling of Ionized Pharmaceuticals in Fish.

Decreasing the tedious sample preparation duration is one of the most important concerns for the environmental analytical chemistry especially for in vivo experiments. However, due to the slow mass diffusion paths for most of the conventional methods, ultrafast in vivo sampling remains challenging. Herein, for the first time, we report an ultrafast in vivo solid-phase microextraction (SPME) device based on electrosorption enhancement and a novel custom-made CNT@PPY@pNE fiber for in vivo sampling of ionized acidic pharmaceuticals in fish. This sampling device exhibited an excellent robustness, reproducibility, matrix effect-resistant capacity, and quantitative ability. Importantly, the extraction kinetics of the targeted ionized pharmaceuticals were significantly accelerated using the device, which significantly improved the sensitivity of the SPME in vivo sampling method (limits of detection ranged from 0.12 ng·g-1 to 0.25 ng·g-1) and shorten the sampling time (only 1 min). The proposed approach was successfully applied to monitor the concentrations of ionized pharmaceuticals in living fish, which demonstrated that the device and fiber were suitable for ultrafast in vivo sampling and continuous monitoring. In addition, the bioconcentration factor (BCF) values of the pharmaceuticals were derived in tilapia (Oreochromis mossambicus) for the first time, based on the data of ultrafast in vivo sampling. Therefore, we developed and validated an effective and ultrafast SPME sampling device for in vivo sampling of ionized analytes in living organisms and this state-of-the-art method provides an alternative technique for future in vivo studies.

Monitoring Dopamine ex Vivo during Electrical Stimulation Using Liquid-Microjunction Surface Sampling.

Liquid-microjunction surface sampling (LMJ-SS) is an ambient ionization technique based on the continuous flow of solvent using an in situ microextraction device in which solvent moves through the probe, drawing in the analytes in preparation for ionization using an electrospray ionization source. However, unlike traditional mass spectrometry (MS) techniques, it operates under ambient pressure and requires no sample preparation, thereby making it ideal for rapid sampling of thicker tissue sections for electrophysiological and other neuroscientific research studies. Studies interrogating neural synapses, or a specific neural circuit, typically employ thick, ex vivo tissue sections maintained under near-physiological conditions to preserve tissue viability and maintain the neural networks. Deep brain stimulation (DBS) is a surgical procedure used to treat the neurological symptoms that are associated with certain neurodegenerative and neuropsychiatric diseases. Parkinson's disease (PD) is a neurological disorder which is commonly treated with DBS therapy. PD is characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta portion of the brain. Here, we demonstrate that the LMJ-SS methodology can provide a platform for ex vivo analysis of the brain during electrical stimulation, such as DBS. We employ LMJ-SS in the ex vivo analysis of mouse brain tissue for monitoring dopamine during electrical stimulation of the striatum region. The mouse brain tissue was sectioned fresh post sacrifice and maintained in artificial cerebrospinal fluid to create near-physiological conditions before direct sampling using LMJ-SS. A selection of metabolites, including time-sensitive metabolites involved in energy regulation in the brain, were identified using standards, and the mass spectral database mzCloud was used to assess the feasibility of the methodology. Thereafter, the intensity of m/z 154 corresponding to protonated dopamine was monitored before and after electrical stimulation of the striatum region, showing an increase in signal directly following a stimulation event. Dopamine is the key neurotransmitter implicated in PD, and although electrochemical detectors have shown such increases in dopamine post-DBS, this is the first study to do so using MS methodologies.

Poly(ionic liquids)-coated stainless-steel wires packed into a polyether ether ketone tube for in-tube solid-phase microextraction.

An in-tube solid-phase microextraction device was developed by packing poly(ionic liquids)-coated stainless-steel wires into a polyether ether ketone tube. An anion-exchange process was performed to enhance the extraction performance. Surface properties of poly(ionic liquids)-coated stainless-steel wires were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. The extraction device was connected to high-performance liquid chromatography equipment to build an online enrichment and analysis system. Ten polycyclic aromatic hydrocarbons were used as model analytes, and important conditions including extraction time and desorption time were optimized. The enrichment factors from 268 to 2497, linear range of 0.03-20μg/L, detection limits of 0.010-0.020μg/L, extraction and preparation repeatability with relative standard deviation less than 1.8 and 19%, respectively were given by the established online analysis method. It has been used to detect polycyclic aromatic hydrocarbons in environmental samples, with the relative recovery (5, 10μg/L) in the range of 85.1-118.9%.

Simple, Low-Cost and Reliable Device for Vacuum-Assisted Headspace Solid-Phase Microextraction of Volatile and Semivolatile Compounds from Complex Solid Samples

A new simple, low-cost, reliable vacuum-assisted headspace solid-phase microextraction (VA-HS-SPME) device was fabricated and evaluated considering the strengths and weaknesses of previously reported systems. The device can be applied for analysis of solid and liquid samples without sample loss or vacuum loss during the evacuation process, in contrast to similar setups. Additionally, it is simpler, lower cost, and more operator friendly for direct extraction of volatiles and semivolatiles from complicated solid matrices. It was coupled with gas chromatography-flame ionization detection (GC-FID) and applied for direct extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in polluted soil samples, without any sample preparation steps. Parameters affecting the performance of the developed method, such as extraction temperature and time, vacuum level, volumes of vacuum chamber and sample vial, and desorption condition, were investigated and optimized. Under the optimal conditions, calibration curves were linear over the range of 0.01–2 μg g−1 (R 2 > 0.996). The limits of detection (LODs) were found to lie in the range of 0.3–0.8 ng g−1, while the relative standard deviations (RSDs) for six replicate analyses were 5.3–7.1%. The developed VA-HS-SPME/GC-FID procedure was used for ultrasensitive determination of PAHs in contaminated soil samples; the results were statistically in agreement with those obtained using a validated ultrasonic solvent extraction (USE) method.

QSAR studies on partition coefficients of organic compounds for polydimethylsiloxane of solid-phase microextraction devices

The solid-phase microextraction (SPME) technique has been widely applied to sample the environmental matrices for organic compounds. The success of employing SPME requires knowledge of the coating-matrix partition coefficients of analytes. Polydimethylsiloxane (PDMS) is the most widely used polymeric coating for the SPME device. In this study, the quantitative structure activity relationships (QSAR) for the PDMS-water (K fw ) and PDMS-gas partition coefficients (K fg ) of organic compounds were established using E-Dragon software and multiple linear regression analysis. K fw was significantly correlated to the BLTA96 descriptor, implying that the PDMS-water partition coefficients were primarily determined by the polarity of analyte molecules. In addition, K fg was significantly dependent on the Harary H index, i.e., molecular connectivity index or polarizability, of the organic compounds. If the organic compounds were grouped in alkanes and aromatic hydrocarbons, K fw and K fg were well proportional to their octanol–water partition coefficients. The statistical results of internal and external validation, determined by the square of the coefficient of multiple correlation (R 2 ≥ 0.865) and the leave-one-out cross-validation (Q 2 ≥ 0.751), showed that the QSAR models developed herein have good stability and great predictive power among the molecular descriptors and SPME/PDMS partition coefficients. The results of this study will facilitate the practical applications of SPME as a greener methodology.

Quantification of VOC emissions from paint spraying on a construction site using solid phase microextraction devices

ABSTRACTThe objective of this study was to measure the emission of, and personal exposure to workers, volatile organic compound (VOC) during paint spraying on a construction site. Needle trap samplers (NTSs), which are a green solid phase microextraction sampling technology, were used to obtain air samples at a large music exhibition center. The standard active sampling method using charcoal tubes and a personal air pump, Method 1501, was simultaneously utilized at the sampling sites to assess the workers’ VOC exposures. Analysis of the data thus obtained showed that benzene, toluene, ethylenebenzene, and xylenes (BTEXs) were the main emission compounds. Acetone and isobutyl alcohol, which are used as thinning solvents, were detected as minor emission compounds. The emitted concentrations of most compounds were lower than the legal emission limits in Taiwan except that of benzene, for which the 2-ppm time weighted average short-term exposure limit was exceeded. The packed divinylbenzene (DVB) in the NTS was observed under an environmental scanning electron microscope, and many fine aerosols were found to be deposited on the surface of the DVB adsorbents, causing VOC extraction efficiencies after the fifth sampling in the field to decline. Workers on construction sites should be protected from emissions of VOC and fine particulates to preserve their occupational health.

Graphene grown on stainless steel mesh as a highly efficient sorbent for sorptive microextraction of polycyclic aromatic hydrocarbons from water samples

In this study, graphene grown on stainless steel mesh efficiently incorporates the advanced properties of graphene in the form of an ultra-thin coating with the open geometry of the substrate, resulting in a highly sensitive and fast sorptive device capable of extracting target analytes directly from sample matrices. The synthesis of graphene on the stainless steel mesh was confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The advantages of the new microextraction device have been investigated for the determination of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples in combination with gas chromatography–flame ionization detector (GC–FID). The factors affecting the extraction efficiency such as stirring speed, extraction time, ionic strength and desorption conditions, were investigated and the optimal extraction conditions were established. Under the optimal extraction condition, linearity was in the range of 0.003–100 ng mL−1 with a correlation coefficient of 0.9923–0.9985. The limits of detection (LODs) of the developed method are obtained between 1 and 3 pg mL−1. The repeatability was assessed at two concentration levels (0.01 and 10 ng mL−1) and the relative standard deviations (RSDs) obtained were 4.9–8.7%. The preparation reproducibility of sorbent device, evaluated with the RSDs, was in the range of 7.3–10.2% (n = 5) in one batch, and 8.3–11.0% (n = 5) among different batches. Finally, the proposed method is applied for the determination of the target PAHs in the real water samples.