Optimization of the Coating Procedure for a High-Throughput 96-Blade Solid Phase Microextraction System Coupled with LC–MS/MS for Analysis of Complex Samples

A 96-position platform for magnetic sorbent-based dispersive microextraction: Application to the determination of tetrahydrocannabinol and cannabidiol in saliva of cannabis smokers

BACKGROUND

In order to obtain sustainable analytical methods, it is essential to develop kinetically efficient sample preparation strategies in which equilibria are reached faster, as dispersive extraction techniques. In addition, the higher the reduction in size, the higher number of extraction vessels can be located and thus the higher number of samples can be simultaneously treated. All this increases sample throughput, and contributes to the reduction of chemical waste, and energy and sample consumption. In this sense, multiposition extraction platforms are smart strategies to achieve these goals, but they are scarcely developed for dispersive extraction techniques.

RESULTS

Taking miniaturized stir bar sorptive dispersive microextraction (mSBSDME) as a starting point, a 96-position extraction platform has been developed using a 96-position stirring plate and a tailor-designed 3D-printed support for locating the miniaturized extraction vessels, achieving a high-throughput miniaturized sample preparation strategy. In order to show the applicability of this novel platform, the determination of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) in human saliva has been carried out and applied to samples collected after the consumption of marijuana and legal CBD-rich cannabis. Only 100 μL of saliva were needed for the analysis and good analytical features in terms of linearity (at least up to 500 ng mL-1), limits of detection (0.7 and 2.8 ng mL-1 for THC and CBD, respectively), and precision (RSD ≤ 14 %) were achieved.

SIGNIFICANCE

The miniaturization of the vessel allows the use of small volumes of sample (i.e., a few microliters) and the treatment of 96 samples in parallel, being the first proposal for carrying out dispersive sorbent-based microextraction under the concept of 96-well format. Additionally, this new workflow contributes to the development of analytical methods that meet the three pillars of sustainability, i.e., greenness and easily affordable in terms of economics and applicability.

Recent solid-phase microextraction-based analytical approaches for the profiling of biliary bile acids in pre-transplant assessments of liver grafts subjected to normothermic ex vivo liver perfusion

BACKGROUND

Liver transplantation is the definitive treatment for end-stage liver failure, but the scarcity of donor organs remains a significant challenge. Leveraging organs from extended criteria donors (ECD) offers a potential avenue to address worldwide shortages, though these organs are more susceptible to post-reperfusion injury. This study explores the use of normothermic ex vivo liver perfusion (NEVLP) as a method for organ preservation - an approach that sustains liver metabolism and facilitates pre-transplant assessments of organ viability via bile analysis. The focal point of this study revolves on the development of analytical methods for determining the bile acid profile throughout the peritransplantation period as a potential indicator of liver function and viability.

RESULTS

The study optimized and validated a high-throughput analytical method to quantify selected bile acids in bile samples using a thin-film microextraction-liquid chromatography-mass spectrometry (TFME-LC-MS) platform. Furthermore, it introduced a solid-phase microextraction-microfluidic open interface-mass spectrometry (SPME-MOI-MS) method for rapid direct analysis of bile acid isobar groups. In the animal study, discernible variations in the concentrations of specific bile acids were observed between donors after circulatory death (DCD) and heart-beating donors (HBD), particularly following normothermic perfusion and reperfusion. Noteworthy fluctuations in individual bile acid concentrations were observed throughout the entire organ transplantation process, with taurocholic acid (TCA), glycocholic acid (GCA), and glycochenodeoxycholic acid (GCDCA) emerging as promising indicators of organ quality. The efficacy of the SPME-MOI-MS platform in corroborating these trends highlights its potential for real-time bile acid analysis during liver transplantation procedures.

SIGNIFICANCE

Our findings underscore the efficacy of NEVLP in tandem with advanced bile acid analysis methods as a reliable strategy for pre-transplant assessments of organ viability, potentially increasing the use of ECD organs and reducing organ shortages. The ability to monitor bile acid profiles in real-time provides crucial insights into liver function and ischemic injury, making significant strides in improving transplant outcomes and patient survival rates.

Flexible nanoplasmonic sensor for multiplexed and rapid quantitative food safety analysis with a thousand-times sensitivity improvement

The accumulation of trace amounts of certain small molecules in food poses considerable human health challenges, including the potential for carcinogenesis and mutagenesis. Here, an ultrasensitive gold-platinum nanoflower-coupled metasurface plasmon resonance (MetaSPR) (APNMSPR) biosensor, based on a competitive immunoassay, was developed for the multiplexed and rapid quantitative analysis of trace small molecules in eggs, offering timely monitoring of food safety. This one-step biosensor can be integrated into either a newly designed detachable high-throughput MetaSPR chip-strip plate device or a standard 96-well plate for multiplexed small-molecule detection within a single egg. The limits of detection were 0.81, 1.12, and 1.74 ppt for florfenicol, fipronil, and enrofloxacin, respectively, demonstrating up to 1000-fold increased sensitivity and a 15-fold reduction in analysis time compared with those of traditional methods. The results obtained using the APNMSPR biosensor showed a strong correlation with those obtained using liquid chromatography-tandem mass spectrometry. The APNMSPR biosensor holds immense promise for the multiplexed, highly sensitive, and rapid quantitative analysis of small molecules for applications in food safety control, early diagnosis, and environmental monitoring.

Octadecyl-fibrous mesoporous silica nanospheres coated 96-blade thin-film microextraction for high-throughput analysis of phthalic acid esters in food and migration from food packages

A high-throughput sample pre-treatment method combined with high-performance liquid chromatography (HPLC) was developed to analyze phthalates (PAEs) in food and food contact package samples. Thin film microextraction (TFME) in 96-blade format was used to pre-treat 96 samples simultaneously. Octadecyl groups functionalized fibrous mesoporous silica nanospheres, namely C18-FMSNs, were synthesized and used as TFME coating material. The coating was fabricated by spraying a slurry of C18-FMSNs and polyacrylontrile (PAN) mixture with a commercial portable spraypen. The prepared C18-FMSNs/PAN coatings exhibited good reproducibility, repeatability and reusability. The optimized TFME conditions for PAEs consisted of extraction at pH 4.0 for 50 min, and desorption by methanol/acetonitrile (25/75, V/V) for 40 min. The pretreatment time for each sample was approximately 1.3 min. This TFME-HPLC method showed good linearity for eight PAEs within the concentration range of 0.5-1000 ng mL-1, with the coefficients higher than 0.9972. The limits of detection and quantification were 0.096-0.26 ng mL-1 and 0.32-0.86 ng mL-1, respectively. The intra-day and inter-day RSD % were below 6.6 % and 8.4 %, respectively, indicating good precision. The PAEs analysis in real samples showed that dibutyl phthalate (DBP) of 2.3 ± 0.3 ng mL-1 and di-(2-ethylhexyl) phthalate (DEHP) of 5.5 ± 0.8 ng mL-1 in boxed milk, dimethyl phthalate (DMP) of 12.6 ± 0.8 ng mL-1, DBP of 3.2 ± 0.4 ng mL-1and DEHP of 14.3 ± 0.7 ng mL-1 in the simulated water migration of plastic box, as well as DMP of 19.0 ± 0.6 ng mL-1, DBP of 25.6 ± 0.9 ng mL-1 and DEHP of 49.5 ± 2.8 ng mL-1 in the simulated ethanol migration of plastic box were determined, respectively. In addition, the detection of PAEs in all the real samples showed good recovery ranging from 85.6 to 110 % and lower RSDs % (<7.2 %).

Developing and Evaluating the Greenness of a Reliable, All-in-One Thin-Film Microextraction Protocol for Determining Fentanyl, Methadone, and Zolpidem in Plasma, Urine, and Oral Fluid

This paper proposes an all-in-one microextraction-based protocol capable of determining and quantifying fentanyl, methadone, and zolpidem in plasma, urine, and saliva at concentrations below those required by international regulatory organizations. A homemade thin-film microextraction device featuring an octyl-cyanopropyl stationary phase was coupled with LC-MS/MS. The proposed method was developed and validated according to FDA criteria, providing extraction efficiency values ranging from 26.7% to 76.2% with no significant matrix effects (2.6% to 15.5% signal suppression). The developed protocol provided low limits of quantification (mostly equal to 1 ng mL-1) and good reproducibility (intra- and inter-day RSDs of less than 9.6% and 12.0%, respectively) and accuracy (89% to 104% of the test concentration). An assessment of the protocol's environmental impact indicated that attention must be devoted to eliminating the use of toxic reagents and developing its capability for in situ sampling and in-field analysis using portable instruments. The proposed TFME-based protocol provides clinical laboratories with a versatile, one-step tool that enables the simultaneous monitoring of fentanyl, methadone, and zolpidem using the most popular biological matrices.

A Solid-Phase Microextraction-Liquid Chromatography-Mass Spectrometry Method for Analyzing Serum Lipids in Psoriatic Disease

Approximately 25% of psoriasis patients have an inflammatory arthritis termed psoriatic arthritis (PsA). There is strong interest in identifying and validating biomarkers that can accurately and reliably predict conversion from psoriasis to PsA using novel technologies such as metabolomics. Lipids, in particular, are of key interest in psoriatic disease. We sought to develop a liquid chromatography-mass spectrometry (LC-MS) method to be used in conjunction with solid-phase microextraction (SPME) for analyzing fatty acids and similar molecules. A total of 25 chromatographic methods based on published lipid studies were tested on two LC columns. As a proof of concept, serum samples from psoriatic disease patients (n = 27 psoriasis and n = 26 PsA) were processed using SPME and run on the selected LC-MS method. The method that was best for analyzing fatty acids and fatty acid-like molecules was optimized and applied to serum samples. A total of 18 tentatively annotated features classified as fatty acids and other lipid compounds were statistically significant between psoriasis and PsA groups using both multivariate and univariate approaches. The SPME-LC-MS method developed and optimized was capable of detecting fatty acids and similar lipids that may aid in differentiating psoriasis and PsA patients.

A rapid single-phase extraction for polar staphylococcal lipids

The lipid membrane is gaining appreciation as a critical factor in the emergence of antibiotic resistance, both for antibiotics that target lipid synthesis or the membrane directly and for cell-wall-targeting antibiotics. The methods used to study the emergence of antibiotic resistance in vitro can generate a large number of samples that may be low in volume and in cell density. As in eukaryotic/mammalian lipidomics, two-phase liquid-liquid extractions are the most commonly used approach to recover lipids from bacteria. The need to separate the lipid layer is cumbersome for high-throughput applications and can be a source of poor reproducibility or contaminant introduction. While several single-phase extractions have been proposed for serum, tissue, and eukaryotic cells, there have been far fewer efforts to adapt or develop such methods for bacteria lipidomics. Here, we describe a simple, single-phase lipid extraction method based on methanol, acetonitrile, and water-the MAW method. The merits of the MAW method are evaluated against the Bligh & Dyer (B&D) method for the recovery of the major membrane lipids (phosphatidylglycerols, diglycosyldiacylglycerols, and lysyl-phosphatidylglycerols) in the Gram-positive pathogen Staphylococcus aureus. We demonstrate that the MAW method achieves recoveries that are comparable to that of the B&D extraction (≥ 85% for PG 15:0/d₇-18:1). The benefits of the MAW method enable the detection of lipids from lower amounts of bacteria than the B&D method (0.57 vs 0.74 McFarlands for PG 32:0, respectively) and is easily scaled down to microplate volumes to facilitate high-throughput studies of bacterial lipids.

Benzodiazepines in complex biological matrices: Recent updates on pretreatment and detection methods

Benzodiazepines (BDZs) are used in clinics for anxiolysis, anticonvulsants, sedative hypnosis, and muscle relaxation. They have high consumptions worldwide because of their easy availability and potential addiction. They are often used for suicide or criminal practices such as abduction and drug-facilitated sexual assault. The pharmacological effects of using small doses of BDZs and their detections from complex biological matrices are challenging. Efficient pretreatment methods followed by accurate and sensitive detections are necessary. Herein, pretreatment methods for the extraction, enrichment, and preconcentration of BDZs as well as the strategies for their screening, identification, and quantitation developed in the past five years have been reviewed. Moreover, recent advances in various methods are summarized. Characteristics and advantages of each method are encompassed. Future directions of the pretreatment and detection methods for BDZs are also reviewed.

Comparison of different approaches for direct coupling of solid-phase microextraction to mass spectrometry for drugs of abuse analysis in plasma

The direct coupling of solid-phase microextraction (SPME) to mass spectrometry (MS) (SPME-MS) has proven to be an effective method for the fast screening and quantitative analysis of compounds in complex matrices such as blood and plasma. In recent years, our lab has developed three novel SPME-MS techniques: SPME-microfluidic open interface-MS (SPME-MOI-MS), coated blade spray-MS (CBS-MS), and SPME-probe electrospray ionization-MS (SPME-PESI-MS). The fast and high-throughput nature of these SPME-MS technologies makes them attractive options for point-of-care analysis and anti-doping testing. However, all these three techniques utilize different SPME geometries and were tested with different MS instruments. Lack of comparative data makes it difficult to determine which of these methodologies is the best option for any given application. This work fills this gap by making a comprehensive comparison of these three technologies with different SPME devices including SPME fibers, CBS blades, and SPME-PESI probes and SPME-liquid chromatography-MS (SPME-LC-MS) for the analysis of drugs of abuse using the same MS instrument. Furthermore, for the first time, we developed different desorption chambers for MOI-MS for coupling with SPME fibers, CBS blades, and SPME-PESI probes, thus illustrating the universality of this approach. In total, eight analytical methods were developed, with the experimental data showing that all the SPME-based methods provided good analytical performance with R ² of linearities larger than 0.9925, accuracies between 81% and 118%, and good precision with an RSD% ≤ 13%.

Biliary Metabolome Profiling for Evaluation of Liver Metabolism and Biliary Tract Function Related to Organ Preservation Method and Degree of Ischemia in a Porcine Model

The development of surgical techniques, immunosuppressive strategies and new organ preservation methods have meant that transplant centers have to face the problem of an insufficient number of organs for transplantation concerning the constantly growing demand. Therefore, using organs from expanded criteria donors and developing new analytical solutions to find parameters or compounds that would allow a more efficient assessment of organ quality before transplantation are options for meeting this challenge. This study proposed bile metabolomic analysis to evaluate liver metabolism and biliary tract function depending on the organ preservation method and degree of warm ischemia time. The analyses were performed on solid-phase microextraction-prepared bile samples from porcine model donors with mild (heart beating donor [HBD]) and moderate warm ischemia (donation after circulatory death [DCD]) grafts subjected to static cold storage (SCS) or normothermic ex vivo liver perfusion (NEVLP) before transplantation. Bile produced in the SCS-preserved livers was characterized by increased levels of metabolites such as chenodeoxycholic acid, arachidonic acid and 5S-hydroxyeicosatetraeonic acid, as well as saturated and monounsaturated lysophosphatidylcholines (LPC). Such changes may be associated with differences in the bile acid synthesis pathways and organ inflammation. Moreover, it has been shown that NEVLP reduced the negative effect of ischemia on organ function. A linear relationship was observed between levels of lipids from the LPC group and the time of organ ischemia. This study identified metabolites worth considering as potential markers of changes occurring in preserved grafts.

Development of the thin film solid phase microextraction (TF-SPME) method for metabolomics profiling of steroidal hormones from urine samples using LC-QTOF/MS

In the present study, the development and optimization of a thin film solid phase microextraction method (TF-SPME) was conducted for metabolomics profiling of eight steroid compounds (androsterone, dihydrotestosterone, dihydroepiandrosterone, estradiol, hydroxyprogesterone, pregnenolone, progesterone and testosterone) from urine samples. For optimization of extraction method, two extraction sorbents (PAN-C18 and PS-DVB) were used as they are known to be effective for isolation of low-polarity analytes. The stages of sample extraction and analyte desorption were considered as the most crucial steps in the process. Regarding the selection of the most suitable desorption solution, six different mixtures were analyzed. As a result, the mixture of ACN: MeOH (1:1, v/v) was chosen in terms of the highest analytes' abundances that were achieved using the chosen solvent. Besides other factors were examined such as the volume of desorption solvent and the time of both extraction and desorption processes. The analytical determination was carried out using the ultra-high performance liquid chromatography coupled with high resolution tandem mass spectrometry detection in electrospray ionization and positive polarity in a scan mode (UHPLC-ESI-QTOF/MS). The developed and optimized TF-SPME method was validated in terms of such parameters as extraction efficiency, recovery as well as matrix effect. As a result, the extraction efficiency and recovery were in a range from 79.3% to 99.2% and from 88.8% to 111.8%, respectively. Matrix effect, calculated as coefficient of variation was less than 15% and was in a range from 1.4% to 11.1%. The values of both validation parameters (recovery and matrix effect) were acceptable in terms of EMA criteria. The proposed TF-SPME method was used successfully for isolation of steroids hormones from pooled urine samples before and after enzymatic hydrolysis of analytes.

Metabolomic fingerprinting of porcine lung tissue during pre-clinical prolonged ex vivo lung perfusion using in vivo SPME coupled with LC-HRMS

Normothermic ex vivo lung perfusion (NEVLP) has emerged as a modernized organ preservation technique that allows for detailed assessment of donor lung function prior to transplantation. The main goal of this study was to identify potential biomarkers of lung function and/or injury during a prolonged (19 h) NEVLP procedure using in vivo solid-phase microextraction (SPME) technology followed by liquid chromatography-high resolution mass spectrometry (LC-HRMS). The use of minimally invasive in vivo SPME fibers for repeated sampling of biological tissue permits the monitoring and evaluation of biochemical changes and alterations in the metabolomic profile of the lung. These in vivo SPME fibers were directly introduced into the lung and were also used to extract metabolites (on-site SPME) from fresh perfusate samples collected alongside lung samplings. A subsequent goal of the study was to assess the feasibility of SPME as an in vivo method in metabolomics studies, in comparison to the traditional in-lab metabolomics workflow. Several upregulated biochemical pathways involved in pro- and anti-inflammatory responses, as well as lipid metabolism, were observed during extended lung perfusion, especially between the 11th and 12th hours of the procedure, in both lung and perfusate samples. However, several unstable and/or short-lived metabolites, such as neuroprostanes, have been extracted from lung tissue in vivo using SPME fibers. On-site monitoring of the metabolomic profiles of both lung tissues through in vivo SPME and perfusate samples on site throughout the prolonged NEVLP procedure can be effectively performed using in vivo SPME technology.

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In vivo SPME monitors metabolic changes in porcine lung during 19-h NEVLP.

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On-site SPME for perfusate sampling monitors metabolite composition during NEVLP.

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SPME-LC-HRMS permits identification of potential metabolic markers of lung function.

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Stored perfusate provides less relevant metabolome information compared to on-site perfusate samples.

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In vivo SPME of the lung provides more metabolomic information than perfusate sampling.

Modifying current thin-film microextraction (TFME) solutions for analyzing prohibited substances: Evaluating new coatings using liquid chromatography

For identifying and quantifying prohibited substances, solid-phase microextraction (SPME) continues to arouse interest as a sample preparation method. However, the practical implementation of this method in routine laboratory testing is currently hindered by the limited number of coatings compatible with the ubiquitous high-performance liquid chromatography (HPLC) systems. Only octadecyl (C18) and polydimethylsiloxane/divinylbenzene ligands are currently marketed for this purpose. To address this situation, the present study evaluated 12 HPLC-compatible coatings, including several chemistries not currently used in this application. The stationary phases of SPME devices in the geometry of thin film-coated blades were prepared by applying silica particles bonded with various functional ligands (C18, octyl, phenyl-hexyl, 3-cyanopropyl, benzenesulfonic acid, and selected combinations of these), as well as unbonded silica, to a metal support. Most of these chemistries have not been previously used as microextraction coatings. The 48 most commonly misused substances were selected to assess the extraction efficacy of each coating, and eight desorption solvent compositions were used to optimize the desorption conditions. All samples were analyzed using an HPLC system coupled with triple quadrupole tandem mass spectrometry. This evaluation enables selection of the best-performing coatings for quantifying prohibited substances and investigates the relationship between extraction efficacy and the physicochemical characteristics of the analytes. Ultimately, using the most suitable coatings is essential for trace-level analysis of chemically diverse prohibited substances.

Polyamide Noncoated Device for Adsorption-Based Microextraction and Novel 3D Printed Thin-Film Microextraction Supports

Polyamide noncoated device for adsorption-based microextraction (PANDA microextraction) is a brand new, easy to prepare, environmentally friendly, inexpensive, and efficient sample preparation method created entirely with the use of 3D printing. The proposed method is based on the extractive proprieties of the unmodified polyamide and carbon fiber blends and is compared with the highly selective thin-film microextraction (TFME). In addition, 3D printing was used to simplify the process of TFME. Prototype sample preparation devices were evaluated by the extraction of oral fluid spiked with 38 small molecules with diverse chemical natures, such as lipophilicity in the log P range of 0.2–7.2. The samples were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry. The results indicate that chemically and thermally resistant 3D printed supports can be successfully used as a cost-saving, environmentally friendly solution for the preparation of TFME devices, alternative to the conventional metal supports, with only marginal differences in the extraction yield (mean = 4.0%, median = 1.8%, range = 0.0–22.3%, n = 38). Even more remarkably, in some cases, the newly proposed PANDA microextraction method exceeded the reference TFME in terms of the extraction efficacy and offered excellent sample cleanup as favorable matrix effects were observed (mean = −8.5%, median = 7.5%, range = −34.7–20.0%, n = 20). This innovative approach paves the road to the simplified sample preparation with the use of emerging extractive 3D printing polymers.

A microchip device based liquid-liquid-solid microextraction for the determination of permethrin and cypermethrin in water samples

In this work, for the first time, a microchip device integrating liquid-liquid-solid phase microextraction is presented. As a novel approach to microchip systems, liquid-liquid-solid microextraction was performed in a sandwiched microchip device. The microchip device consisted of three poly(methyl methacrylate) layers along with a double "Y"-shaped microchannel. As the stationary phase, polyacrylonitrile-C18 was synthesized and immobilized in the upper channel, while the beneath channel was used as a reservoir for the stagnant volume ratio of sample-to-extraction solvent phase. In this way, analytes were extracted from an aqueous sample through an organic phase into the stationary phase. The analytes were finally desorbed with a minimum amount of acetonitrile as the desorption solvent. Permethrin and cypermethrin were selected as the model analytes for extraction and subsequent analysis by gas chromatography-flame ionization detection. Under optimum conditions (extraction solvent; n-hexane, sample -to-extraction solvent volume ratio; 2:1, extraction time; 20 min, desorption solvent; acetonitrile, desorption volume; 200 μL, and desorption time; 15 min) detection limits were 3.5 and 6.0 ng mL^-1 for permethrin and cypermethrin, respectively. Relative standard deviations for intra- and inter-day reproducibility were below 8.3%. Device-to-device precision was in the range of 8.1-9.6%. The proposed microchip device was successfully applied to determine permethrin and cypermethrin in water samples with recoveries in the range of 73-96%.

[Solid phase microextraction-high performance liquid chromatography of fluorinated covalent organic polymer to determine eugenol anesthetics in aquatic products]

Fluorinated covalent organic polymers (F-COPs) constitute a new class of porous materials with a topological structure, large surface area, and potential superiority over other types of polymers in sample preparation. In this study, a F-COP was rapidly synthesized by a simple Schiff-based reaction using 2,3,5,6-tetrafluoroterephthalaldehyde (TFA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) as monomers, and by adding scandium (Ⅲ) triflate (Sc(OTf)3) as the metal catalyst at room temperature. The prepared F-COP was applied as a coating adsorbent for solid phase microextraction (SPME) to enrich three kinds of eugenol anesthetics in aquatic products. The extraction performance of an enrichment medium is an important factor for practical application in real analytical projects. This F-COP adsorbent with rich π-stacking electrons contained abundant phenyl rings and imine (-C=N) groups throughout the molecular framework. The adsorption mechanism was explored and discussed based on the π-π affinity and hydrogen bonding interaction, which contributed to its strong recognition affinity to targets. The F-COP was characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, and scanning electron microscopy (SEM). The results indicated that the novel F-COP-SPME bar exhibited a rough and porous surface structure, good preparation reproducibility, and high stability. High performance liquid chromatography (HPLC) was performed with an ultraviolet-visible (UV-vis) wavelength detector. A Diamonsil plus C18 column (250 mm×4.6 mm, 5 μm) was used as the analytical column. The mobile phase comprised 60% methanol and 40% ultrapure water, and was flowed at 0.800 mL/min. The injected volume of the sample was 20.0 μL. The column temperature was maintained at 30 ℃ and the detection wavelength was set to 280 nm. Further, the SPME conditions (including extraction time, stirring rate, desorption solvent, and desorption time) that influenced the extraction efficiencies of the eugenol anesthetics were investigated in detail. Thus, the optimized F-COP-SPME bar conditions were established as follows: extraction time: 30 min; stirring rate: 700 r/min; desorption solvent: acetonitrile; desorption time: 10 min. By combining F-COP-based SPME with HPLC-UV analysis, an effective method was developed for the extraction and determination of eugenol, eugenyl acetate, and methyl eugenol residues in aquatic products. The method demonstrated good linearity in the range of 10-1000 μg/L for eugenol and eugenyl acetate, and 10-1500 μg/L for methyl eugenol, with correlation coefficients (r2) greater than 0.9961, low limits of detection (2.9-4.5 μg/kg, S/N=3), and excellent precision (relative standard deviations lower than 8.7%, n=5). Finally, the method was applied for the effective extraction of three kinds of eugenol anesthetics from tilapia and shrimp samples. The obtained recoveries were in the range of 76.7%-98.7% and 80.3%-104% with relative standard deviations of 8.5%-11.8% and 8.6%-12.4% (n=5), respectively. These results demonstrated that the F-COP is promising for use as an adsorbent in SPME for the determination of eugenol anesthetics in aquatic products. The developed method was suitable for the qualitative and quantitative determination of three kinds of eugenol anesthetics in aquatic products, yielding a satisfactory purification effect and sensitivity.

Benefits of Innovative and Fully Water-Compatible Stationary Phases of Thin-Film Microextraction (TFME) Blades

Octadecyl (C₁₈) groups are arguably the most popular ligands used for preparation of solid phase microextraction (SPME) devices. However, conventional C₁₈-bonded silica particles are not fully compatible with the nearly 100% aqueous composition of typical biological samples (e.g., plasma, saliva, or urine). This study presents the first evaluation of thin-film SPME devices coated with special water-compatible C₁₈-bonded particles. Device performance was assessed by extracting a mixture of 30 model compounds that exhibited various chemical structures and properties, such as hydrophobicity. Additionally, nine unique compositions of desorption solvents were tested. Thin-film SPME devices coated with C₁₈-bonded silica particles with polar end-capping groups (10 µm) were compared with conventional trimethylsilane end-capped C₁₈-bonded silica particles of various sizes (5, 10, and 45 µm) and characteristics. Polar end-capped particles provided the best extraction efficacy and were characterized by the strongest correlations between the efficacy of the extraction process and the hydrophobicity of the analytes. The results suggest that the original features of octadecyl ligands are best preserved in aqueous conditions by polar end-capped particles, unlike with conventional trimethylsilane end-capped particles that are currently used to prepare SPME devices. The benefits associated with this improved type of coating encourage further implementation of microextractraction as greener alternative to the traditional sample preparation methods.

Thin film molecularly imprinted polymer (TF-MIP), a selective and single-use extraction device for high-throughput analysis of biological samples

Enhancing selectivity, reducing matrix effects and increasing analytical throughput have been the main objectives in the development of biological sample preparation techniques. A thin film molecularly imprinted polymer (MIP) is employed for extraction and analysis of tricyclic antidepressants (TCAs) as a model class of compounds in human plasma for the first time to reach the abovementioned goals. The thin film MIPs prepared on a metal substrate can be used directly for extraction from biological matrices with no sample manipulation steps and no pre-conditioning. This method was validated with good linearity (R² > 0.99 in 1.0-500.0 ng mL^-1 range), excellent accuracy (90% -110%) and precision (RSD % value less than 15%) in pooled human plasma samples (N = 3). The limits of quantitation (LOQ) for TCAs in plasma samples were between 1.0-5.0 ng mL^-1 which are lower than the therapeutic ranges of these drugs. Kinetic and isotherm studies showed the superior performance of MIP sorbent compared to a non-imprinted polymer (NIP) sorbent in extracting TCAs from a bovine serum albumin (BSA) solution. The optimized and validated method for pooled human plasma was utilized for monitoring the concentration of TCAs in three patient samples who had been prescribed TCAs. These selective single-use thin film extraction devices are promising for efficient and fast procedures for analyzing biological samples.

High-throughput biomonitoring of organophosphate flame-retardant metabolites in urine via 96-blade solid-phase microextraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry

Organophosphate flame retardants (OPFRs) are widely used in consumer products and building materials, but their propensity for migration poses a problem with respect to polluting indoor environments, water, soil, and dust. OPFR metabolites in urine samples are appropriate biomarkers for assessing exposure risk levels. In this paper, a high-throughput method that couples 96-blade solid-phase microextraction with ultra-performance liquid chromatography-tandem mass spectrometry (SPME-UPLC-MS/MS) is applied for the simultaneous detection of four OPFR metabolites in urine samples. The results indicated that the best extraction was achieved using 96 blades coated with hydrophilic-lipophilic balance weak anion exchange (HLB-WAX). The proposed SPME method's extraction efficiency was maximized by optimizing extraction time, pH value, desorption solution, desorption volume, and desorption time, and it was validated in accordance with the Food and Drug Administration's guidelines. The findings indicated that the proposed method has a wide linearity range (0.5-100 ng mL^-1) and low detection limits (0.09-0.14 ng mL^-1). The method's accuracy ranged from 98% to 118%, with intra-day precision ranging from 1% to 10%. In contrast, inter-day precision ranged from 3% to 16%. Accuracy was also evaluated using independent urine samples, which ranged from 78% to 124% with corresponding relative standard deviations (1%-16%). Ultimately, DoCP was detected in two real samples at a concentration of 0.5-1.1 ng mL^-1, and BEHP was detected at a concentration of 0.2-1.2 ng mL^-1. Overall, the proposed SPME-UPLC-MS/MS method is reliable, accurate, and capable of simultaneously determining four OPFR metabolites in urine samples and screening them to assess exposure risk for humans.

Metabolic Evaluation of Urine from Patients Diagnosed with High Grade (HG) Bladder Cancer by SPME-LC-MS Method

Bladder cancer (BC) is a common malignancy of the urinary system and a leading cause of death worldwide. In this work, untargeted metabolomic profiling of biological fluids is presented as a non-invasive tool for bladder cancer biomarker discovery as a first step towards developing superior methods for detection, treatment, and prevention well as to further our current understanding of this disease. In this study, urine samples from 24 healthy volunteers and 24 BC patients were subjected to metabolomic profiling using high throughput solid-phase microextraction (SPME) in thin-film format and reversed-phase high-performance liquid chromatography coupled with a Q Exactive Focus Orbitrap mass spectrometer. The chemometric analysis enabled the selection of metabolites contributing to the observed separation of BC patients from the control group. Relevant differences were demonstrated for phenylalanine metabolism compounds, i.e., benzoic acid, hippuric acid, and 4-hydroxycinnamic acid. Furthermore, compounds involved in the metabolism of histidine, beta-alanine, and glycerophospholipids were also identified. Thin-film SPME can be efficiently used as an alternative approach to other traditional urine sample preparation methods, demonstrating the SPME technique as a simple and efficient tool for urinary metabolomics research. Moreover, this study's results may support a better understanding of bladder cancer development and progression mechanisms.

Therapeutic drug monitoring of tranexamic acid in plasma and urine of renally impaired patients using solid phase microextraction

The purpose of the research was to develop an improved solid phase microextraction (SPME)-based sampling protocol for the therapeutic drug monitoring of tranexamic acid (TXA) from plasma and urine of patients with chronic renal dysfunction (CRD) in order to correct the current dosing schedule to accommodate these patients. A 12-fold improvement in sampling efficiency (25 min for 96 samples -22 s per sample) was achieved with the use of hydrophilic-lipophilic balance (HLB)-coated SPME devices, thereby enabling high throughput profiling of TXA in the plasma and urine of 49 CRD patients undergoing cardiac surgery. A limit of quantification of 10 μg/mL and 25 μg/mL was obtained for plasma and urine respectively while a method accuracy of 103-105% and a precision of less than 8% was achieved. The results from this study were ultimately used by clinicians at the Toronto General Hospital to design a corrective pharmacokinetic dosing schedule for CRD patients. This green method further presents potential application in the clinical field for the fast high throughput monitoring of TXA not only in plasma but also in urine - a biological matrix seldom explored for the analysis of TXA - without the need for solvent-assisted extraction, extensive sample pre-treatment or clean-up, derivatization or excessive pH adjustment to improve amenability for analytical separation.

Nanoparticle-based polyacrylonitrile monolithic column for highly efficient micro solid-phase extraction of carotenoids and vitamins in human serum

In this work, a biocompatible monolithic column based micro-solid-phase extraction (µ-SPE) method was developed for biological fluid analysis. A novel nanoparticle-based polyacrylonitrile monolithic column (C30 NP-PMC) was fabricated by incorporating triacontyl (C30) modified silica nanoparticles (NPs) into the polyacrylonitrile monolithic matrix through thermally induced phase separation. With efficient mass transfer and sorption capacity, C30 NP-PMC exhibited outstanding performance for the extraction of carotenoids and fat-soluble vitamins (FSVs) from human serum samples, superior to commercial C18 cartridges as well as liquid-liquid extraction (LLE) method. Under optimal conditions, the proposed µ-SPE method coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD) achieved satisfactory limits of detection (LODs) (1.5-75.0 ng/mL) and good recoveries (85.0-106.5 %) with relative standard deviations (RSDs) of less than 12.1% by consuming lower sorbent (35.0 mg) and organic solvent (0.8 mL). Successful application of the developed method demonstrated the great potential of such monolithic sorbents for efficient isolation and preconcentration of trace analytes from blood samples.

An innovative sampling approach combined with liquid chromatography-tandem mass spectrometry for the analysis of emerging pollutants in drinking water

In this work, an innovative sampling and preconcentration method followed by analysis with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization (LC-ESI-MS/MS) was developed for the determination of different emerging pollutants (five anti-inflammatory drugs and one antibacterial agent) in water matrices. Thin-film microextraction blades, consisting of stainless steel blades with a coating made of divinylbenzene, have been employed. The blades, fixed onto a stainless steel support, were mounted on a laboratory stirrer with adjustable speed, immersed in water samples and eluted with methanol. The analytical procedure was developed, carefully optimizing stirring speed and extraction time. A good reproducibility among the blades was observed; quantitation limits at the ng L^-1 level were achieved. Calibration curves were constructed by applying the whole procedure to tap water samples, free from analytes, spiked with standards in the concentration range 0.01-2 μg L^-1 ; good linearity was obtained, with R² between 0.9984 and 0.9991. The optimized method was applied to tap and surface waters; two anti-inflammatory drugs were detected at the ng L^-1 level in surface water. In one sample, diclofenac and naproxen were measured at 26 ± 5 and 15 ± 1 ng L^-1 , respectively; only diclofenac was quantified in the other sample at 14 ± 3 ng L^-1 .

Systematic Evaluation of Different Coating Chemistries Used in Thin-Film Microextraction

A systematic evaluation of eight different coatings made of solid phase extraction (SPE) and carbon-based sorbents immobilized with polyacrylonitrile in the thin-film microextraction (TFME) format using LC-MS/MS was described. The investigated coatings included graphene, graphene oxide, multi-walled carbon nanotubes (MWCNTs), carboxylated MWCNTs, as carbon-based coatings, and polystyrene-divinylbenzene (PS-DVB), octadecyl-silica particles (C18), hydrophilic-hydrophobic balance particles (HLB) and phenyl-boronic acid modified particles (PBA), as SPE-based coatings. A total of 24 compounds of diverse moieties and of a wide range of polarities (log P from -2.99 to 6.98) were selected as probes. The investigated coatings were characterized based on their extraction performance toward the selected probes at different pH values and at optimized desorption conditions. In the case of SPE-based coatings, PS-DVB and HLB exhibited a balanced extraction for compounds within a wide range of polarities, and C18 showed superior extraction recoveries for non-polar analytes. Carbon-based coatings showed high affinity for non-polar compounds given that their main driving force for extraction is hydrophobic interactions. Interestingly, among the studied carbon-based coatings, graphene oxide showed the best extraction capabilities toward polar compounds owing to its oxygen-containing groups. Overall, this work provided important insights about the extraction mechanisms and properties of the investigated coatings, facilitating the coating selection when developing new TFME applications.

Development of a thin-film solid-phase microextraction (TF-SPME) method coupled to liquid chromatography and tandem mass spectrometry for high-throughput determination of steroid hormones in white sucker fish plasma

Steroid hormones (SH) play a number of important physiological roles in vertebrates including fish. Changes in SH concentration significantly affect reproduction, differentiation, development, or metabolism. The objective of this study was to develop an in vitro high-throughput thin-film solid-phase microextraction (TF-SPME)-liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for targeted analysis of endogenous SH (cortisol, testosterone, progesterone, estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2)) in wild white sucker fish plasma where the concentrations of the analytes are substantially low. A simple TF-SPME method enabled the simultaneous determination of free and total SH concentrations. The use of biocompatible coating allowed direct extraction of these hormones from complex biological samples without prior preparation. The carryover was less than 3%, thereby ensuring reusability of the devices and reproducibility. The results showed that TF-SPME was suitable for the analysis of compounds in the polarity range between 1.28 and 4.31 such as SH at different physicochemical properties. The proposed method was validated according to bioanalytical method validation guidelines. The limit of detection (LOD) and limit of quantification(LOQ) for cortisol, testosterone, progesterone, E1, E2, and EE2 were from 0.006 to 0.150 ng/mL and from 0.020 to 0.500 ng/mL, respectively. The recovery for the method was about 85%, and the accuracy and precision of the method for cortisol, testosterone, and progesterone were ≤ 6.0% and ≤ 11.2%, respectively, whereas those for E1, E2, and EE2 were ≤ 15.0% and ≤ 10.2%, respectively. On the basis of this study, TF-SPME demonstrated several important advantages such as simplicity, sensitivity, and robustness under laboratory conditions. Graphical abstract.

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.

Unique Solid Phase Microextraction Sampler Reveals Distinctive Biogeochemical Profiles among Various Deep-Sea Hydrothermal Vents

Current methods for biochemical and biogeochemical analysis of the deep-sea hydrothermal vent ecosystems rely on water sample recovery, or in situ analysis using underwater instruments with limited range of analyte detection and limited sensitivity. Even in cases where large quantities of sample are recovered, labile dissolved organic compounds may not be detected due to time delays between sampling and preservation. Here, we present a novel approach for in situ extraction of organic compounds from hydrothermal vent fluids through a unique solid phase microextraction (SPME) sampler. These samplers were deployed to sample effluent of vents on sulphide chimneys, located on Axial Seamount in the North-East Pacific, in the Urashima field on the southern Mariana back-arc, and at the Hafa Adai site in the central Mariana back-arc. Among the compounds that were extracted, a wide range of unique organic compounds, including labile dissolved organic sulfur compounds, were detected through high-resolution LC-MS/MS, among which were biomarkers of anammox bacteria, fungi, and lower animals. This report is the first to show that SPME can contribute to a broader understanding of deep sea ecology and biogeochemical cycles in hydrothermal vent ecosystems.

Introducing a mechanically robust SPME sampler for the on-site sampling and extraction of a wide range of untargeted pollutants in environmental waters

The present study introduces a mechanically robust, sealable SPME sampler for the on-site sampling and extraction of a wide range of untargeted pollutants in environmental waters. Spray-coating and dip coating methodologies were used to coat the surfaces of six stainless steel bolts with a layer of HLB/PAN particles, which served as the extractive substrate in the proposed device. In addition, this sampler was designed to withstand rough handling, long storage times, and various environmental conditions. In order to identify whether the sampler was able to stabilize extracted compounds for long periods of time, the effects of storage time and temperature were evaluated. The results of these tests showed no significant differences in the quantity and quality of the extracted chemicals following 12 days storage at room temperature, thus confirming the device's suitability for use at sampling sites that are far away from the laboratory facilities. The proposed device was also used to perform extraction and untargeted analyses of river waters in five different geographical locations. The constituent chemicals in the samplers were analyzed and determined using high-resolution HPLC-Orbitrap MS. Toxin and Toxin-Target Database was used as a reference database for toxins and environmental contaminants. Ultimately, over 80 tentative chemicals with widely varying hydrophobicities ranging within -2.43 < logP <11.9-including drugs, metabolites, wide ranges of toxins, pesticide, and insecticides-were identified in the samplers used in the different rivers. The log P values for the tentative analytes confirmed that the introduced device is suitable for the extraction and trace analysis of wide ranges of targeted and untargeted pollutants.

High-Throughput and High-Efficient Micro-solid Phase Extraction Based on Sulfonated-Polyaniline/Polyacrylonitrile Nanofiber Mats for Determination of Fluoroquinolones in Animal-Origin Foods

We herein describe a high-throughput 96-well plate micro-solid phase extraction sample preparation technique based on novel sulfonated-polyaniline/polyacrylonitrile nanofiber mats (sulfonated-PANI/PAN NFMs) for multiresidue detection of fluoroquinolones (FQs) in various animal-origin food samples. Through the double-modification of polyaniline and sulfonic acid, the resulting functionalized sulfonated-PANI/PAN NFMs present high extraction efficiency for FQs. Compared with the existing methods, this approach demonstrates its advantages of being suitable for more sample matrices (milk, animal muscle, liver, kidney, and egg), lower sample amount (0.5 g), lower sorbent requirement (5.0 mg), lower volume of organic solvent (0.7 mL), shorter time (0.2 min per sample), and high sensitivity (0.012-0.06 μg·kg^-1). In addition, sulfonated-PANI/PAN NFMs possess excellent reusability which could be reused 10 times without an obvious decrease in extraction efficiency. Combined with ultra performance liquid chromatography-tandem mass spectrometry, the novel sample preparation technique can be expected as an efficient method for routine trace FQ residue monitoring in animal-origin food samples.

Application of 3D-printed scabbard-like sorbent for sample preparation in bioanalysis expanded to 96-wellplate high-throughput format

Modern bioanalysis, which involves the quantitative and qualitative determination of small-molecule endogenous and exogenous substances in biological samples, is a powerful and useful tool that can generate valuable information related to many areas connected with human health and quality of life. Although LC-MS and GC-MS are widely viewed as the gold standards for many bioanalytical tasks, the scientific community has not abandoned its search for newer, more efficient, and more inexpensive methods of performing extraction as a sample preparation step before final analysis. Recent research showing the immense potential of 3D printing compelled our group to explore how this technology could be applied to techniques used in analytical chemistry. In particular, 3D printing offers three promising advantages: availability, low cost of materials and equipment, and the ability to fabricate objects of nearly any shape to suit the needs of a given application. Previously, we demonstrated that a commercial 3D material (LAY-FOMM) can function as a chemically active object that enables the reversible sorption of the antidiabetic drug, glimepiride, and endogenous steroids. In this report, we use a 3D printer to fabricate sorbents with a scabbard-like shape for use with a 96-blade system, which, along with the use of a 96-well plate, allows multiple extractions to be performed simultaneously. In order to assess the relative benefits of this 3D printed approach, we compare the performance of the proposed LAY-FOMM-based sorbent to that of the widely used C18 sorbent. Although the LAY-FOMM sorbent showed lower extraction recovery rates than the C18 sorbent, all of the other validation parameters suggest that it is suitable for use in high-throughput analysis of steroids in human plasma.

In vivo solid-phase microextraction sampling combined with metabolomics and toxicological studies for the non-lethal monitoring of the exposome in fish tissue

Various environmental studies have employed the biomonitoring of fish in their aquatic ecosystems in order to identify potential metabolic responses to the exposome. In this study, we applied in vivo solid-phase microextraction (SPME) to perform non-lethal sampling on the muscle tissue of living fish to extract toxicants and various endogenous metabolites. Sixty white suckers (Catastomus commersonii) were sampled from sites upstream, adjacent, and downstream from the oil sands development region of the Athabasca River (Alberta, Canada) in order to track their biochemical responses to potential contaminants. In vivo SPME sampling facilitated the extraction of a wide range of endogenous metabolites, mainly related to lipid metabolism. The obtained results revealed significant changes in the levels of numerous metabolites, including eicosanoids, linoleic acids, and fat-soluble vitamins, in fish sampled in different areas of the river, thus demonstrating SPME's applicability for the direct monitoring of exposure to different environmental toxicants. In addition, several classes of toxins, including petroleum-related compounds, that can cause serious physiological impairment were tentatively identified in the extracts. In vivo SPME, combined with the analysis of contaminants and endogenous metabolites, provided important information about the exposome; as such, this approach represents a potentially powerful and non-lethal tool for identifying the mechanisms that produce altered metabolic pathways in response to the mixtures of different environmental pollutants.

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.

High throughput bar adsorptive microextraction: A novel cost-effective tool for monitoring benzodiazepines in large number of biological samples

In this work, we propose an innovative high throughput (HT) apparatus using the bar adsorptive microextraction (BAμE) technique, which enables the simultaneous enrichment of up to 100 samples. This novel configuration was combined with microliquid desorption and high-performance liquid chromatography-diode array detection to monitor trace levels of eight benzodiazepines (diazepam, prazepam, bromazepam, oxazepam, lorazepam, alprazolam, temazepam and loflazepate) in biological samples. The proposed methodology was fully developed, optimized and validated, resulting in suitable intraday and interday precision (RSD ≤ 15%), with recovery yields ranging from 33.0% to 104.5%. The lower limits of quantification were between 20.0 and 100.0 µg L^-1, using 1.0 mL of urine and 0.5 mL of plasma or serum samples. The application of the proposed methodology to real matrices resulted in average sample preparation time of around 2 min per sample, demonstrating that it is user-friendly, cost-effective and a rapid decision-making tool, whenever large number of samples are involved.

High-Throughput Solid-Phase Microextraction-Liquid Chromatography-Mass Spectrometry for Microbial Untargeted Metabolomics

Nowadays, metabolomics data, when combined with other "omics" data, can provide important information regarding systems biology. Acquiring a comprehensive untargeted metabolome snapshot of complex sample matrices requires proper sample preparation, and access to sophisticated analytical instrumentation such as mass spectrometry. In metabolomics, sample preparation has substantial influence on the quality of the obtained metabolome profile. To achieve a real snapshot of the metabolome, the analysis method must be capable of inhibiting metabolite interconversion by immediately quenching all metabolome activity. Application of solid-phase microextraction (SPME), particularly in its in vivo set up, when undertaken in conjunction with a conscious selection of coating type based on the chosen sample matrix and the physicochemical properties of the analytes under study, is capable of providing extraction of representative metabolomes for many biological matrices. Metabolomes identified by SPME include low-abundance species and short-lived or unstable metabolites hardly captured by traditional extraction techniques. SPME coupled to liquid chromatography-high-resolution mass spectrometry has recently been introduced as an innovative alternative technique that integrates sampling, sample preparation, and extraction for metabolic profiling and isolation of candidate biomarkers. This chapter presents a detailed protocol for microbial metabolome analysis of Escherichia coli as a model organism, applying the high-throughput SPME-LC-MS workflow.