Preparation of a Particle-Loaded Membrane for Trace Gas Sampling

Evaluation of thin film microextraction based on graphene oxide/ polymer composite: Experimental and theoretical insights

Experimental and theoretical assessments of a graphene oxide-based polymer as adsorbent for thin film microextraction (TFME) were conducted as part of this research. Graphene oxide (GO) was embedded in the organic polymer poly(styrene-co-divinylbenzene) (PS-DVB) to prepare a sorbent suitable for direct-immersion TFME. A TFME membrane coating prepared with the GO/PS-DVB sorbent and polydimethylsiloxane (PDMS) as binder was then applied for extraction of organic pollutants from aqueous and gaseous samples. The surface morphology of the TFME coating was examined by scanning electron microscopy (SEM). Various TFME parameters influencing extraction efficiency, such as extraction time and temperature, desorption temperature, and ionic strength, were investigated and optimized. In a comparison of TFME membranes, the GO/PS-DVB/PDMS TFME membrane was shown to yield higher extraction efficiencies for the targeted analytes than the pure PDMS and DVB/PDMS TFME membranes. The calibration graphs of the organic pollutants displayed linearity for most of the target analytes within the 10-2000 ng L-1 concentration range. The repeatability (RSD %, n = 5) and reproducibility (RSD %, n = 3) of the method were in the ranges of 2.2-5.9 %, and 3.2-8.5 %, respectively, at a concentration level of 500 ng L-1, whereas accuracy (%) ranged between 79.8 and 119 %. The developed method was successfully applied for determinations of organic pollutants in tap water, lake water, and wastewater samples. Furthermore, the impact of mass transfer kinetics on extractions by the GO/PS-DVB/PDMS TFME membrane from gaseous samples was theoretically discussed and experimentally verified. The results of this work demonstrate that the GO/PS-DVB/PDMS TFME method is a simple, efficient, and environmentally friendly method for pre-treatment of organic pollutants.

High throughput and automated solid-phase microextraction and determination by liquid chromatography-mass spectrometry for the analysis of mycotoxins in beer

There is high demand for rapid screening of toxics in food analysis. In this study, a new high-throughput and automated solid-phase microextraction (SPME) system was employed for the sample preparation of mycotoxins in beers. Matrix compatible SPME blades with thin coating layer were used, which significantly decreased the matrix effects in beer samples (≤ 12%). This SPME system allows 96 samples to be processed automatically and simultaneously with average preparation time of 57 s per sample. After sample preparation, the 96-well plate with desorption solution was sealed with a thin film and put into the LC-MS sampler for analysis via positive/negative ESI switching mode. The results also showed good sensitivity (limits of detection between 0.02 and 3 ng/mL) with R²≥ 0.9971, reproducibility (intra- and inter-day ≤ 8% and ≤ 13%, respectively), and accuracy (recoveries between 79% and 121%).

Rapid detection and speciation of illicit drugs via a thin-film microextraction approach for wastewater-based epidemiology study

High detection frequency of illicit drugs in water samples urges the development of rapid detection method for wastewater-based epidemiology (WBE) study. Here, we first developed a fast, convenient, and cost-effective method by combining thin-film microextraction (TFME) with gas chromatography-mass spectrometry (GC-MS) for sensing illicit drugs in wastewater sample. A divinylbenzene particle-loaded membrane was prepared by dip coating on a copper mesh. The sampling conditions of three illicit drugs were optimized and the performance of the proposed method was evaluated. The limit of detection was 5.5 2.0, and 1.1 ng L^-1 for methamphetamine (MAMP), ketamine (KET), and methaqualone (MEQA), respectively, with acceptable precision (< 6.1 % for membrane to membrane reproducibility) and recovery from influent water (95 % - 111 %). Then, the proposed method was applied to study the occurrence and distribution of the target compounds in a wastewater treatment plant. The presence of methamphetamine, ketamine, and methaqualone was confirmed and their concentrations in the influent sample were 57 ± 8, 40 ± 4, and 75 ± 2 ng L^-1, respectively. The speciation of the target compounds in different ponds was also investigated. Results showed that the content of organic matter and the pH of the sample significantly affected the binding state of the compounds. This work provides an efficient and accurate analytical protocol for WBE investigation of illicit drugs.

Sample bottle coated with sorbent as a novel solid-phase extraction device for rapid on-site detection of BTEX in water

Solid-phase extraction (SPE) is a popular technique for environmental sample pretreatment. However, SPE usually requires complex sample pretreatment processes, which is time-consuming and inconvenient for real-time and on-site monitoring. Herein, a solvent-free, rapid, and user-friendly SPE device was developed by coating the polydimethylsiloxane (PDMS)/divinylbenzene (DVB) sorbent on the inner wall of a sample bottle. The extraction process and desorption process were both carried out in the bottle. The analytes trapped in the sorbent were thermally desorbed and simultaneously sucked out from the bottle by an air sampling tube equipped on field-portable GC-MS. Different to previous work, the sample pretreatment process didn't require any complicated and time-consuming steps, such as centrifugation or filtration. The total analysis time for each sample was less than 25 min, which was feasible for rapid on-site detection, and thus avoided the losses and contamination of samples in conventional sample storage and transportation processes. Under optimal conditions, the proposed SPE method exhibited wide linear ranges, low detection limits (0.010-0.036 μg L^-1, which were much lower than the maximum levels restricted by the US Environmental Protection Agency and the Chinese GB3838-2002 standard), good intra-bottle repeatability (6.13-7.17%, n = 3) and satisfactory inter-bottle reproducibility (4.73-6.47%, n = 3). Finally, the method was successfully applied to the rapid detection of BTEX in the field. The recoveries of BTEX in spiked water samples ranged from 89.1% to 116.2%. This work presents a novel SPE approach for rapid on-site monitoring in water samples.

Development of a Drone-Based Thin-Film Solid-Phase Microextraction Water Sampler to Facilitate On-Site Screening of Environmental Pollutants

To simplify on-site water sampling and screening, particularly in hard-to-reach or dangerous sites, a drone equipped with a hydrophilic-lipophilic balance (HLB), thin-film solid-phase microextraction (TF-SPME) sampler was developed. The drone-based sampler was shown to protect the sorbent phase from external contamination while preventing any detectable loss of components of a spiked modified McReynolds mixture on the membrane in the sampler for at least 10 min. HLB/poly(dimethylsiloxane) (PDMS) membranes deployed in flight on the drone sampler were demonstrated to extract disinfection by-products, including trichloromethane, dichloroacetonitrile, 1,1,1-trichloro-2-propanone, 2,2,2-trichloroethanol, benzonitrile, and benzyl nitrile, from hot tub water. When analyzed on-site, in duplicate, using hand-portable instrumentation, reasonably repeatable results were achieved (%relative standard deviations (RSD's) 5-16%). Finally, drone TF-SPME sampling of an anthropogenically impacted watercourse indicated that impact from the suspected nearby landfill site was minimal, instead suggesting that internal combustion by-products from vehicles on the nearby Highway 401 played a much larger role in contaminating the watercourse. This conclusion was supported by the confirmed presence of BTEX, styrene, isopropylbenzene, propylbenzene, and 1,3,5-trimethylbenzene. In addition to immediately identifying these compounds on-site using portable gas chromatography-mass spectrometry (GC-MS), samples were taken back to the laboratory for benchtop analysis, further supporting this conclusion.

Development of a solid-phase microextraction LC-MS/MS method for determination of oxidative stress biomarkers in biofluids

Recently the connection between oxidative stress and various diseases, including cancer and Alzheimer's, attracts notice as a pathway suitable for diagnostic purposes. 8-Oxo-deoxyguanosine and 8-oxo-deoxyadenosine produced from the interaction of reactive oxygen species with DNA become prominent as biomarkers. Several methods have been developed for their determination in biofluids, including solid-phase extraction and enzyme-linked immunosorbent assays. However, still, there is a need for reliable and fast analytical methods. In this context, solid-phase microextraction offers many advantages such as flexibility in geometry and applicable sample volume, as well as high adaptability to high-throughput sampling. In this study, a solid-phase microextraction method was developed for the determination of 8-oxo-deoxyguanosine and 8-oxo-deoxyadenosine in biofluids. The extractive phase of solid-phase microextraction consisted of hydrophilic-lipophilic balanced polymeric particles. In order to develop a solid-phase microextraction method suitable for the determination of the analytes in saliva and urine, several parameters, including desorption solvent, desorption time, sample pH, and ionic strength, were scrutinized. Analytical figures of merit indicated that the developed method provides reasonable interday and intraday precisions (<15% in both biofluids) with acceptable accuracy. The method provides a limit of quantification for both biomarkers at 5.0 and 10.0 ng/mL levels in saliva and urine matrices, respectively.

Development, Optimization and Applications of Thin Film Solid Phase Microextraction (TF-SPME) Devices for Thermal Desorption: A Comprehensive Review

Through the development of solid phase microextraction (SPME) technologies, thin film solid phase microextraction (TF-SPME) has been repeatedly validated as a novel sampling device well suited for various applications. These applications, encompassing a wide range of sampling methods such as onsite, in vivo and routine analysis, benefit greatly from the convenience and sensitivity TF-SPME offers. TF-SPME, having both an increased extraction phase volume and surface area to volume ratio compared to conventional microextraction techniques, allows high extraction rates and enhanced capacity, making it a convenient and ideal sampling tool for ultra-trace level analysis. This review provides a comprehensive discussion on the development of TF-SPME and the applications it has provided thus far. Emphasis is given on its application to thermal desorption, with method development and optimization for this desorption method discussed in detail. Moreover, a detailed outlook on the current progress of TF-SPME development and its future is also discussed with emphasis on its applications to environmental, food and fragrance analysis.

A review of developments and applications of thin-film microextraction coupled to surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) greatly expands the applications of Raman spectroscopy and is a promising technique for food safety, environmental analysis, and public safety. Thin-film microextraction (TFME) provides an efficient sample preparation method for SERS to improve its selectivity and detection efficiency. This review comprehensively describes the development and applications of SERS and TFME, including the history, mechanisim, and active substrate of SERS and the theory, device, forms, and practical applications of TFME. The applications of TFME-SERS in food safety and environment monitoring are discussed, which could improve their advantages. TFME extracts and enriches the target analytes to eliminate the interfering substance, providing a facial way for SERS to analyze the target analytes in complex matrices. The development of TFME-SERS technology not only expands the application range of TFME, but greatly improves the anti-interference ability and detection sensitivity of SERS. Thus, the established methods are fast, convenient, and highly sensitive. This technology is potential to be applied in the on-site and real-time detection.

Fast screening of illicit drugs in beverages and biological fluids by direct coupling of thin film microextraction to dielectric barrier discharge ionization-mass spectrometry

A direct and fast method for quantification of illicit drugs in beverages and biological fluids was developed, using dielectric barrier discharge ionization in combination with high-resolution MS.

Review of geometries and coating materials in solid phase microextraction: Opportunities, limitations, and future perspectives

The development of new support and geometries of solid phase microextraction (SPME), including metal fiber assemblies, coated-tip, and thin film microextraction (TFME) (i.e. self-supported, fabric and blade supported), as well as their effects on diffusion and extraction rate of analytes were discussed in the current review. Application of main techniques widely used for preparation of a variety of coating materials of SPME, including sol-gel technique, electrochemical and electrospinning methods as well as the available commercial coatings, were presented. Advantages and limitations of each technique from several aspects, such as range of application, biocompatibility, availability in different geometrical configurations, method of preparation, incorporation of various materials to tune the coating properties, and thermal and physical stability, were also investigated. Future perspectives of each technique to improve the efficiency and stability of the coatings were also summarized. Some interesting materials including ionic liquids (ILs), metal organic frameworks (MOFs) and particle loaded coatings were briefly presented.

Sample preparation with solid phase microextraction and exhaustive extraction approaches: Comparison for challenging cases

In chemical analysis, sample preparation is frequently considered the bottleneck of the entire analytical method. The success of the final method strongly depends on understanding the entire process of analysis of a particular type of analyte in a sample, namely: the physicochemical properties of the analytes (solubility, volatility, polarity etc.), the environmental conditions, and the matrix components of the sample. Various sample preparation strategies have been developed based on exhaustive or non-exhaustive extraction of analytes from matrices. Undoubtedly, amongst all sample preparation approaches, liquid extraction, including liquid-liquid (LLE) and solid phase extraction (SPE), are the most well-known, widely used, and commonly accepted methods by many international organizations and accredited laboratories. Both methods are well documented and there are many well defined procedures, which make them, at first sight, the methods of choice. However, many challenging tasks, such as complex matrix applications, on-site and in vivo applications, and determination of matrix-bound and free concentrations of analytes, are not easily attainable with these classical approaches for sample preparation. In the last two decades, the introduction of solid phase microextraction (SPME) has brought significant progress in the sample preparation area by facilitating on-site and in vivo applications, time weighted average (TWA) and instantaneous concentration determinations. Recently introduced matrix compatible coatings for SPME facilitate direct extraction from complex matrices and fill the gap in direct sampling from challenging matrices. Following introduction of SPME, numerous other microextraction approaches evolved to address limitations of the above mentioned techniques. There is not a single method that can be considered as a universal solution for sample preparation. This review aims to show the main advantages and limitations of the above mentioned sample preparation approaches and the applicability and capability of each technique for challenging cases such as complex matrices, on-site applications and automation.