Selective capillary coating materials for in-tube solid-phase microextraction coupled to liquid chromatography to determine drugs and biomarkers in biological samples: A review

Modified stainless steel wires with superwettability for highly efficient in-tube solid-phase microextraction

Construction of different surface wettability is meaningful for the interaction between the sorbent surface and target components. In the current study, four kinds of stainless-steel wires (SSWs) with different hydrophobic/hydrophilic property were prepared and used as the absorbents to enrich the target compounds with different polarity. Comparative extraction of six non-polar polycyclic aromatic hydrocarbons (PAHs) and six polar estrogens was carried out by in-tube solid phase microextraction (IT-SPME). The results showed that two SSWs with the superhydrophobic surfaces exhibited high extraction capacity to the non-polar PAHs with the superior enrichment factor (EF) in the range of 29-672 and 57-744, respectively. In contrast, the superhydrophilic SSWs demonstrated higher enrichment efficiency for the polar estrogens than other hydrophobic SSWs. On the basis of optimized conditions, a validated analysis method was established using six PAHs as model analytes for IT-SPME-HPLC. Acceptable linear ranges (0.5-10 μg L^-1) and low detection limits (0.0056-0.32 μg L^-1) were achieved using the superhydrophobic wire modified by perfluorooctyl trichlorosilane (FOTS). The relative recoveries spiked at 2, 5 and 10 μg L^-1 in the lake water samples were in the range of 81.5%-113.7%. The relative standard deviation (RSD) of intraday (≤0.8%, n = 3) and interday (≤5.3%, n = 3) tests demonstrated the good extraction repeatability for the same extraction tube. Satisfactory repeatability for the preparation of extraction tubes (n = 3) was also obtained with the RSD values in the range of 3.6%-8.0%.

In-Tube Solid-Phase Microextraction Directly Coupled to Mass Spectrometric Systems: A Review

Since it was introduced in 1997, in-tube solid-phase microextraction (in-tube SPME), which uses a capillary column as extraction device, has been continuously developed as online microextraction coupled to LC systems (in-tube SPME-LC). In the last decade, new couplings have been evaluated on the basis of state-of-the-art LC instruments, including direct coupling of in-tube SPME to MS/MS systems, without chromatographic separation, for high-throughput analysis. In-tube SPME coupling to MS/MS has been possible thanks to the selectivity of capillary column coatings and MS/MS systems (SRM mode). Different types of capillary columns (wall-coated open-tubular, porous-layer open-tubular, sorbent-packed, porous monolithic rods, or fiber-packed) with selective stationary phases have been developed to increase the sorption capacity and selectivity of in-tube SPME. This review focuses on the in-tube SPME principle, extraction configurations, current advances in direct coupling to MS/MS systems, experimental parameters, coatings, and applications in different areas (food, biological, clinical, and environmental areas) over the last years.

Analysis of Different Methods of Extracting NSAIDs in Biological Fluid Samples for LC-MS/MS Assays: Scoping Review

The aim of this study was to carry out a systematic investigation and analysis of different drug extraction methods, specifically non-steroidal anti-inflammatory drugs in biological fluid samples, for Liquid Chromatography in Mass Spectrometry assays (LC-MS/MS). A search was carried out in the main databases between 1999 and 2021, following the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) checklist. Data were obtained through PubMed, Lilacs, Embase, Scopus, and Web of Science databases using the Boolean operators AND and OR. Studies were pre-selected by title and abstract by two independent reviewers. The selected texts were read in full, and only those that were complete and compatible with the inclusion and exclusion criteria were eligible for this research. A total of 248 references were obtained in the databases. After removing the duplicates and analyzing the titles and abstracts, 79 references were evaluated and passed to the next phase, which comprised the complete reading of the article. A total of 39 publications were eligible for this study. In 52% of the studies, the authors used the liquid–liquid extraction method (LLE), while in 41%, the solid-phase extraction method (SPE) was used. A total of 5% used microextraction methods and 2% used less-conventional techniques. The literature on the main methods used, the LLE and SPE methods, is extensive and consolidated; however, we found other studies that reported modifications of these traditional techniques, which were equally validated for use in LC-MS/MS. From this review, it is concluded that the diversity of techniques, reliability, and practical information about each analytical method used in this study can be adapted to advances in LC-MS/MS techniques; however, more ecological, economic, and sustainable approaches should be explored in the future.

In situ photo-initiated polymerized oligonucleotide-functionalized hydrophilic capillary affinity monolith for highly selective in-tube microextraction of ochratoxin A mycotoxin

A photo-initiated polymerized oligonucleotide-grafted hydrophilic affinity monolithic column was synthesized in situ, and exploited for selective in-tube solid phase micro-extraction (IT-SPME) protocol towards the sensitive detection of ochratoxin A (OTA). Only 7 min was required for the rapid polymerization of aptamer-based affinity monolith, which was much less than the reaction time of most thermal polymerization (12-16 h) and sol-gel chemistry methods (up to 52 h). Characterizations such as polymerization recipes, structure morphology, FTIR spectrum, elemental mapping, mechanical stability, and specific recognition performance were evaluated. A significantly hydrophilic nature with a low contact angle of 15° was observed, and a mixed-mode mechanism including aptamer affinity recognition and hydrophilic interaction (HI) was employed. By coupling with HPLC-fluorescence detection, the highly specific online recognition performance was achieved with an extremely low nonspecific adsorption of the analogues. The calibration curve of OTA was obtained in the concentration range 0.05-50.00 ng·mL^-1 with a limit of detection (LOD, S/N = 3) of 0.012 ng·mL^-1. Applied to sample analysis, acceptable recovery yields of 95.1 ± 1.4% - 99.5 ± 2.2% (n = 3) were obtained in beer and red wine. The proposed method lighted a promising way to efficiently preparing a hydrophilic aptamer-affinity monolith for highly specific recognition of trace mycotoxin by IT-SPME coupled with HPLC. A hydrophilic oligonucleotide-based affinity capillary monolith was explored via in situ photopolymerization for overcoming low preparation efficiency and achieving high-performance online IT-SPME of OTA mycotoxin.

Innovative extraction materials for fiber-in-tube solid phase microextraction: A review

Fiber-in-tube solid-phase microextraction (fiber-in-tube SPME) with short capillary longitudinally packed with fine fibers as extraction device allows direct coupling to high performance liquid chromatography (HPLC) systems to determine weakly volatile or thermally labile compounds. This technique associates the advantages of miniaturized and analytical on-line systems. Major achievements include the use of different capillaries (fused-silica, copper, stainless steel, polyetheretherketone (PEEK), or poly(tetrafluoroethylene) (PTFE)) that are packed with neat fibers (Zylon®, silk, or Kevlar 29®) or fibers (stainless steel, basalt, or carbon) functionalized with selective coatings (aerogels, ionic liquids (ILs), polymeric ionic liquids (PILs), molecularly imprinted polymers (MIPs), layered double hydroxides (LDHs), or conducting polymer). This review outlines the fundamental theory and the innovative extraction materials for fiber-in-tube SPME-HPLC systems and highlights their main applications in environmental and bioanalyses.

Carbonized Aramid Fiber as the Adsorbent for In-Tube Solid-Phase Microextraction to Detect Estrogens in Water Samples

Carbonized aramid fiber was prepared as a new type of adsorbent for in-tube solid-phase microextraction. The surface structure, chemical composition, and graphitization degree of the resulted fiber was determined and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectrometry. The prepared fiber was packed in a stainless-steel tube instead of the sample loop of a six-port and tested for the extraction of five environmental estrogen hormones coupled with high-performance liquid chromatography. Several parameters affecting the estrogens’ extraction including the sampling volume, sampling rate, NaCl content, and desorption time were investigated in detail. The extraction tube with carbonized aramid fiber exhibited remarkable extraction performance towards five estrogen targets. The analysis method was established, and it exhibited a wide linear range (0.5–10.0 μg/L) with good linearity (correlation coefficient ≥0.9906), low limits of detection (0.011–0.13 μg/L), and high enrichment factors (178–1335) for the five analytes. Relative standard deviations (n = 3) for intraday (≤4.8%) and interday (≤4.0%) tests indicated that the extraction material had satisfactory repeatability. Bisphenol A released from a polycarbonate (PC) bottle was quantitatively detected with a concentration of 8.3 μg/L. The relative recoveries spiked at 5 and 10 μg/L were investigated, and the results were in the range of 74.3–121% for real water samples.

Selective analysis of interferon-alpha in human serum with boronate affinity oriented imprinting based plastic antibody

Interferons are important biomolecules in human immune system. Cytokine interferon alpha (IFN-α), a type I interferon, is one of the major components of the innate immune response involved in autoimmune diseases. Thus, the analysis of interferons is of great importance for both biological and pharmaceutical purposes. In this work, an IFN-α specific plastic antibody is prepared via boronate affinity oriented surface imprinting. By combing with the magnetic nanoparticles, the imprinted material exhibits several advantages, including strong affinity (K_d: 75.2 nM), high specificity (cross reactivity<25%), excellent efficiency (imprinting efficiency: 44.1%), tolerance to interferences, and easy manipulation. By employing the prepared imprinted material as sorbent for selective enrichment of IFN-α, a good linearity is achieved in the range of 50 ng/mL-10 μg/mL, and the detection and quantifcation limits are 10 ng/mL and 50 ng/mL respectively. The recoveries of this approach are found within 75.8%-82.2% with relative standard deviations of 6.4-9.7%. Furthermore, the IFN-α in spiked human serum is analyzed with acceptable reliability (recovery: 77.3%, RSD: 7.9%). Because of these highly desirable properties, the IFN-α specific plastic antibody can find more applications in medical and pharmaceutical industry.

Advances and applications of in-tube solid-phase microextraction for analysis of proteins

In-tube solid-phase microextraction (IT-SPME) with capillary column as extraction device is a well-established green extraction technique with a lot of applications in the fields of biomedicine, food and environment. This article reviews the research contributions of IT-SPME for analysis of proteins. The paper first briefly describes the history of IT-SPME. Then, the development and principle of IT-SPME for analysis of proteins are introduced, in which capillary column configurations of IT-SPME and instruments for quantitative analysis of proteins are summarized. Subsequently, the synthesis strategy and recognition principle of different recognition units, including antibodies, aptamers, molecularly imprinted polymers, and boronate affinity materials, are discussed in detail. This part also introduces several rare recognition units, including lectins, restricted access materials, lysine modified with β-cyclodextrin and cell membrane. The development trend and possible future direction of IT-SPME for analysis of proteins are mentioned.

Applications of porous frameworks in solid-phase microextraction

Porous frameworks are a term of attracting solid materials assembled by interconnection of molecules and ions. These trendy materials due to high chemical and thermal stability, well-defined pore size and structure, and high effective surface area gained attention to employ as extraction phase in sample pretreatment methods before analytical analysis. Solid-phase microextraction is an important subclass of sample preparation technique that up to now different configurations of this method have been introduced to get adaptable with different environments and analytical instruments. In this review, theoretical aspect and different modes of solid-phase microextraction method are investigated. Different classes of porous frameworks and their applications as extraction phase in the proposed microextraction method are evaluated. Types and features of supporting substrates and coating procedures of porous frameworks on them are reviewed. At the end, the prospective and the challenges ahead in this field are discussed.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.

Simultaneous enrichment and analysis of benzimidazole by in-tube SPME-MS based on poly (3-Acrylamidophenylboronic acid-co-divinylbenzene-co-N,N'-methylenebisacrylamide) monolithic column

In this work, a sensitive, rapid, and matrix effect-free method for online simultaneous detection of benzimidazoles in animal products by in-tube solid-phase microextraction coupled with mass spectrometry (in-tube SPME-MS) was investigated. Herein, according to the chemical structures properites of the analyte benzimidazoles, poly (3-Acrylamidophenylboronic acid-co-divinylbenzene-co-N,N'-Methylenebisacryladmide) [poly (AAPBA-co-DVB-co-MBAA)] microextraction column was prepared, and severs as the extraction and enrichment medium (in-tube SPME) via hydrophobic, B-N coordination, π-π, and hydrogen bonding interactions with the benzimidazoles. The monolithic column was optimized and characterized, showing satisfactory permeability and extraction capacity in range of 514-1000 μg mL^-1 for the benzimidazoles. The important parameters of the in-tube SPME-MS system experimental condition were systematically optimized to achieve the maximal extraction efficiency. Under the optimized condition, the MS intensity of benzimidazoles measured by in-tube SPME-MS is more significant, cleaner, and has a better signal-to-noise ratio than the mass intensity measured by direct MS method. Good linearity was obtained with correlation coefficients between 0.9915 and 0.9990, and the detection limits (S/N = 3) of the benzimidazoles were between 0.55 and 0.91 ng g^-1. Recoveries in the range of 72.5%-92.4% were obtained for the benzimidazoles in pork and chicken in three spiked concentration levels, with satisfactory relative standard deviations (n = 4) that lower than 7.5%. The developed in-tube SPME-MS method based on the poly (AAPBA-co-DVB-co-MBAA) column was successfully used to sensitively determine trace benzimidazoles in animal products without interference peaks, indicating that it is promising for the analysis of benzimidazoles in practical samples that requiring minimal sample pre-treatment and no chromatographic separation.

Fluorescent nanomaterials combined with molecular imprinting polymer: synthesis, analytical applications, and challenges

Fluorescent nanomaterials (FNMs) and molecular imprinted polymers (MIPs) have been widely used in analytical chemistry for determination. However, low selectivity of FNMs and low sensitivity of MIPs hinder their applications. Combining the merits of FNMs and MIPs, FNMs coated with MIPs (FNMs@MIPs) were proposed to solve those problems. Carbon dots, semiconductor quantum dots, noble metal nanoparticles, silica nanoparticles, and covalent-organic frameworks have been reported to be coated with MIPs. In order to overcome challenges for FNMs@MIPs, such as the lack of handy synthesis routes, incompatibility with aqueous solutions, heterogeneous size of particles, leakage of template molecules, the biocompatibility of FNMs@MIPs, and the inference between FNMs and MIPs, scientists proposed some solutions in recent years. We comprehensively review the newest advances of the FNMs@MIPs, and predict the direction of the future development. Graphical abstract.

Sample treatment based on molecularly imprinted polymers for the analysis of veterinary drugs in food samples: a review

The use of veterinary drugs in medical treatments and in the livestock industry is a recurrent practice. When applied in subtherapeutic doses over prolonged times, they can also act as growth promoters. However, residues of these substances in foods present a risk to human health. Their analysis is thus important and can help guarantee consumer safety. The critical point in each analytical technique is the sample treatment and the analytical matrix complexity. The present manuscript summarizes the development, type of synthesis, characterization, and application of molecularly imprinted polymers in the separation, identification, and quantification techniques for the determination of veterinary drug residues in food samples in extraction, clean-up, isolation, and pre-concentration systems. Synthesized sorbents with specific recognition properties improve the interactions between the analytes and the polymeric sorbents, providing better analysis conditions and advantages in comparison with commercial sorbents in terms of high selectivity, analytical sensitivity, easy performance, and low cost analysis.

Recent Advances in the Extraction of Polycyclic Aromatic Hydrocarbons from Environmental Samples

Polycyclic aromatic hydrocarbons (PAHs) comprise a group of chemical compounds consisting of two or more fused benzene rings. PAHs exhibit hydrophobicity and low water solubility, while some of their members are toxic substances resistant to degradation. Due to their low levels in environmental matrices, a preconcentration step is usually required for their determination. Nowadays, there is a wide variety of sample preparation techniques, including micro-extraction techniques (e.g., solid-phase microextraction and liquid phase microextraction) and miniaturized extraction techniques (e.g., dispersive solid-phase extraction, magnetic solid-phase extraction, stir bar sorptive extraction, fabric phase sorptive extraction etc.). Compared to the conventional sample preparation techniques, these novel techniques show some benefits, including reduced organic solvent consumption, while they are time and cost efficient. A plethora of adsorbents, such as metal-organic frameworks, carbon-based materials and molecularly imprinted polymers, have been successfully coupled with a wide variety of extraction techniques. This review focuses on the recent advances in the extraction techniques of PAHs from environmental matrices, utilizing novel sample preparation approaches and adsorbents.

Bioanalytical HPLC Applications of In-Tube Solid Phase Microextraction: A Two-Decade Overview

In-tube solid phase microextraction is a cutting-edge sample treatment technique offering significant advantages in terms of miniaturization, green character, automation, and preconcentration prior to analysis. During the past years, there has been a considerable increase in the reported publications, as well as in the research groups focusing their activities on this technique. In the present review article, HPLC bioanalytical applications of in-tube SPME are discussed, covering a wide time frame of twenty years of research reports. Instrumental aspects towards the coupling of in-tube SPME and HPLC are also discussed, and detailed information on materials/coatings and applications in biological samples are provided.

Restricted access carbon nanotube for microextraction by packed sorbent to determine antipsychotics in plasma samples by high-performance liquid chromatography-tandem mass spectrometry

This manuscript describes the development of the restricted access carbon nanotube (RACNT) as a selective stationary phase for microextraction by packed sorbent (MEPS) to determine antipsychotics (chlorpromazine, clozapine, olanzapine, and quetiapine) in untreated plasma samples from schizophrenic patients by ultra-high liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The synthesis was achieved by chemically covering commercial multi-walled carbon nanotubes with bovine serum albumin (BSA) to subsequently pack the material in a polyethylene conical tube (1000 μL). The RACNTs' sorbents were able to exclude about 97% of the plasma proteins, maintaining the same performance for about 100 assays. The MEPS variables (sample pH, draw-eject cycles, desorption and phase cleanup) were evaluated to improve sensibility and selectivity. The MEPS/UHPLC-MS/MS method was linear at concentrations ranging from the lower limit of quantification (10.0 ng mL^-1) to the upper limit of quantification (200-700 ng mL^-1) with coefficients of determinations higher than 0.99. The precision assays presented relative standard deviation (RSD) values lower than 13%, and the accuracy assays presented relative error (RE) values that ranged from - 8.01 to 11.53%. Neither significant matrix effects nor carryover was observed. The developed method was successfully applied to determine antipsychotics drugs for therapeutic drug monitoring of schizophrenic patients.

Preparation and application of immunoaffinity in-tube solid phase microextraction column with oriented antibody-immobilized porous layer open tubular capillary for high sensitive quantification of serum extracellular domain of human epidermal growth factor receptor 2 levels

Human epidermal growth factor receptor 2 (HER2) gene expresses a transmembrane glycoprotein that is over-expressed in 15-30% breast, 3% lung, and other several digestive cancers. So HER2 is a good biomarker for tumor diagnostic and treatment monitoring. Clinically, detection of HER2 often employs invasive approaches with tissue samples, which at large extent limit its universal application. Shedding of the extracellular domain (ECD) of the HER2 (HER2-ECD) into the circulation has led to the development of a serum test of HER2-ECD as an additional approach to probe the HER2 overexpression. However, few methods were developed due to the high sensitivity required by the serum HER2-ECD determination. In this work, we prepared a novel immunoaffinity in-tube solid phase microextraction (IT-SPME) sorbent for selective enrichment of HER2-ECD. Two clinical available monoclonal antibodies against to HER2, trastuzumab and pertuzumab, were selected as immunoaffinity ligands. Porous layer open tubular capillary with oriented antibody immobilization were fabricated and systematically optimized to afford a higher extraction capacity. The capacity was reached to 120.4 μg/m, which is more than 1000 times higher than that obtained by a common method (directly antibody immobilization on a naked capillary). After sample extraction and enrichment by the IT-SPME, the eluent were determined by a particle-enhanced turbidimetric immunoassay (PETIA). Sensitive quantification of HER2-ECD by the PETIA was thereby accomplished. HER2-ECD concentrations in 82 clinical serum samples were determined by the developed IT-SPME/PETIA method, and the results were well-correlated with that by the clinical used chemiluminescence immunoassay (CLIA). Besides, the IT-SPME/PETIA method was found providing 5 times higher sensitivity than the CLIA, and 500 times higher than the PETIA without IT-SPME. The results indicate that the developed method is suitable for high-sensitive quantification of HER2-ECD in clinical samples.

Developing a novel packed in-tube solid-phase extraction method for determination ∆ 9-tetrahydrocannabinol in biological samples and cannabis leaves

A novel plate-like nano-sorbent based on copper/cobalt/chromium layered double hydroxide was synthesized by a simple coprecipitation method. The synthesized nanoparticels were introduced into a stainless steel cartridge using a dry packing method. Then, the packed cartridge was introduced as a novel on-line "packed in-tube" configuration and followed by high performance liquid chromatography for the determination of trace amounts of ^∆ 9-tetrahydrocannabinol from biological samples and cannabis leaves. The as-prepared sorbent exhibited long lifetime, good chemical stability, and high anion-exchange capacity. Several important factors affecting the extraction efficiency, such as extraction and desorption times, pH of the sample solution and flow rates of the sample and eluent solutions, were investigated and optimized. Under optimized conditions, this method showed good linearity for ^∆ 9-tetrahydrocannabinol in the ranges of 0.09-500, 0.3-500, and 0.4-500 µg/L with coefficients of determination of 0.9999, 0.9991, and 0.9994 in water, serum and plasma samples, respectively. The inter- and intra-assay precisions (n = 3) were respectively in the ranges of 1.8-4.6% and 1.9-4.0% at three concentration levels of 10, 50, and 100 µg/L. The limits of detection were also in the range of 0.02-0.1 µg/L.

Recent developments and emerging trends of mass spectrometric methods in plant hormone analysis: a review

Plant hormones are naturally occurring small molecule compounds which are present at trace amounts in plant. They play a pivotal role in the regulation of plant growth. The biological activity of plant hormones depends on their concentrations in the plant, thus, accurate determination of plant hormone is paramount. However, the complex plant matrix, wide polarity range and low concentration of plant hormones are the main hindrances to effective analyses of plant hormone even when state-of-the-art analytical techniques are employed. These factors substantially influence the accuracy of analytical results. So far, significant progress has been realized in the analysis of plant hormones, particularly in sample pretreatment techniques and mass spectrometric methods. This review describes the classic extraction and modern microextraction techniques used to analyze plant hormone. Advancements in solid phase microextraction (SPME) methods have been driven by the ever-increasing requirement for dynamic and in vivo identification of the spatial distribution of plant hormones in real-life plant samples, which would contribute greatly to the burgeoning field of plant hormone investigation. In this review, we describe advances in various aspects of mass spectrometry methods. Many fragmentation patterns are analyzed to provide the theoretical basis for the establishment of a mass spectral database for the analysis of plant hormones. We hope to provide a technical guide for further discovery of new plant hormones. More than 140 research studies on plant hormone published in the past decade are reviewed, with a particular emphasis on the recent advances in mass spectrometry and sample pretreatment techniques in the analysis of plant hormone. The potential progress for further research in plant hormones analysis is also highlighted.

A Dual Ligand Sol⁻Gel Organic-Silica Hybrid Monolithic Capillary for In-Tube SPME-MS/MS to Determine Amino Acids in Plasma Samples

This work describes the direct coupling of the in-tube solid-phase microextraction (in-tube SPME) technique to a tandem mass spectrometry system (MS/MS) to determine amino acids (AA) and neurotransmitters (NT) (alanine, serine, isoleucine, leucine, aspartic acid, glutamic acid, lysine, methionine, tyrosine, and tryptophan) in plasma samples from schizophrenic patients. An innovative organic-silica hybrid monolithic capillary with bifunctional groups (amino and cyano) was developed and evaluated as an extraction device for in-tube SPME. The morphological and structural aspects of the monolithic phase were evaluated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), nitrogen sorption experiments, X-ray diffraction (XRD) analyses, and adsorption experiments. In-tube SPME-MS/MS conditions were established to remove matrix, enrich analytes (monolithic capillary) and improve the sensitivity of the MS/MS system. The proposed method was linear from 45 to 360 ng mL^-1 for alanine, from 15 to 300 ng mL^-1 for leucine and isoleucine, from 12 to 102 ng mL^-1 for methionine, from 10 to 102 ng mL^-1 for tyrosine, from 9 to 96 ng mL^-1 for tryptophan, from 12 to 210 ng mL^-1 for serine, from 12 to 90 ng mL^-1 for glutamic acid, from 12 to 102 ng mL^-1 for lysine, and from 6 to 36 ng mL^-1 for aspartic acid. The precision of intra-assays and inter-assays presented CV values ranged from 1.6% to 14.0%. The accuracy of intra-assays and inter-assays presented RSE values from -11.0% to 13.8%, with the exception of the lower limit of quantification (LLOQ) values. The in-tube SPME-MS/MS method was successfully applied to determine the target AA and NT in plasma samples from schizophrenic patients.

Simultaneous HPLC-MS determination of 8-hydroxy-2'-deoxyguanosine, 3-hydroxyphenanthrene and 1-hydroxypyrene after online in-tube solid phase microextraction using a graphene oxide/poly(3,4-ethylenedioxythiophene)/polypyrrole composite

The exploration of monohydroxy polycyclic aromatic hydrocarbons and 8-hydroxy-2'-deoxyguanosine (8-OHdG) produced by oxidative stress and DNA damage is a powerful and non-invasive tool to study the health risk of exposure to polycyclic aromatic hydrocarbons (PAHs). A nanocomposite prepared from graphene oxide, poly(3,4-ethylenedioxythiophene) and polypyrrole was electrodeposited on the internal surface of a stainless-steel tube for online in-tube solid phase microextraction (IT-SPME) of 8-OHdG, 3-hydroxyphenanthrene and 1-hydroxypyrene from urine. The coating possesses excellent chemical and mechanical stability, high extraction efficiency, good resistance to matrix interference, and a long lifespan. An online IT-SPME-high performance liquid chromatography-mass spectrometry method was developed for the determination of these three metabolite biomarkers in human urine. Figures of merit include (a) enrichment factors of 30-48; (b) low limits of detection (4-41 pg·mL^-1 at S/N = 3); (c) wide linear ranges (0.05-50 ng·mL^-1); (d) good recoveries from spiked samples (71.6-109.5%); and (e) acceptable repeatability (2.3-14.6%). The method offers the advantages of low cost, simplicity, sensitivity, rapidity and automation. Graphical abstract Schematic illustration of online in-tube solid phase microextraction using graphene oxide/poly(3,4-ethylenedioxythiophene)/polypyrrole composites as adsorbent in a stainless-steel (SS) tube for the enrichment and simultaneous determination of 8-hydroxy-2'-deoxyguanosine, 3-hydroxyphenanthrene and 1-hydroxypyrene prior to HPLC-MS analysis.

Butyl Methacrylate-Co-Ethylene Glycol Dimethacrylate Monolith for Online in-Tube SPME-UHPLC-MS/MS to Determine Chlopromazine, Clozapine, Quetiapine, Olanzapine, and Their Metabolites in Plasma Samples

This manuscript describes a sensitive, selective, and online in-tube solid-phase microextraction coupled with an ultrahigh performance liquid chromatography-tandem mass spectrometry (in-tube SPME-UHPLC-MS/MS) method to determine chlopromazine, clozapine, quetiapine, olanzapine, and their metabolites in plasma samples from schizophrenic patients. Organic poly(butyl methacrylate-co-ethylene glycol dimethacrylate) monolith was synthesized on the internal surface of a fused silica capillary (covalent bonds) for in-tube SPME. Analyte extraction and analysis was conducted by connecting the monolithic capillary to an UHPLC-MS/MS system. The monolith was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The developed method presented adequate linearity for all the target antipsychotics: R² was higher than 0.9975, lack-of-fit ranged from 0.115 to 0.955, precision had variation coefficients lower than 14.2%, and accuracy had relative standard error values ranging from -13.5% to 14.6%, with the exception of the lower limit of quantification (LLOQ). The LLOQ values in plasma samples were 10 ng mL^-1 for all analytes. The developed method was successfully applied to determine antipsychotics and their metabolites in plasma samples from schizophrenic patients.

A novel aptamer-based online magnetic solid phase extraction method for the selective determination of 8-hydroxy-2'-deoxyguanosine in human urine

In this work, an innovative magnetic aptamer adsorbent (Fe₃O₄-aptamer MNPs) was synthesized for the selective extraction of 8-hydroxy-2'-deoxyguanosine (8-OHdG). Amino-functionalized-Fe₃O₄ was crosslinked with 8-OHdG aptamer by glutaraldehyde and fixed into a steel stainless tube as the sorbent of magnetic solid phase extraction (MSPE). After selective extraction by the aptamer adsorbent, the adsorbed 8-OHdG was desorbed dynamically and online analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS). The synthesized sorbent presented outstanding features, including specific selectivity, high enrichment capacity, stability and biocompatibility. Moreover, this proposed MSPE-HPLC-MS can achieve adsorption and desorption operation integration, greatly simplify the analysis process and reduce human errors. When compared with offline MSPE, a sensitivity enhancement of 800 times was obtained for the online method. Some experimental parameters such as the amount of the sorbent, sample flow rate and sample volume, were optimized systematically. Under the optimal conditions, low limit of detection (0.01 ng mL^-1, S/N = 3), limit of quantity (0.03 ng mL^-1, S/N = 10) and wide linear range with a satisfactory correlation coefficient (R² ≥ 0.9992) were obtained. And the recoveries of 8-OHdG in the urine samples varied from 82% to 116%. All these results revealed that the method is simple, rapid, selective, sensitive and automated, and it could be expected to become a potential approach for the selective determination of trace 8-OHdG in complex urinary samples.

An organically modified silica aerogel for online in-tube solid-phase microextraction

Aerogels have received considerable attentions because of its porous, high specific surface, unique properties and environmental friendliness. In this work, an organically modified silica aerogel was functionalized on the basalt fibers (BFs) and filled into a poly(ether ether ketone) (PEEK) tube, which was coupled with high performance liquid chromatography (HPLC) for in-tube solid-phase microextraction (IT-SPME). The aerogel was characterized by scanning electron microscopy (SEM) and fourier transform infrared spectrometry (FT-IR). The extraction efficiency of the tube was systematically investigated and shown enrichment factors from 2346 to 3132. An automated, sensitive and selective method was developed for the determination of five estrogens. The linear range was from 0.03 to 100μgL^-1 with correlation coefficients (r) higher than 0.9989, and low detection limits (LODs) were 0.01-0.05μgL^-1. The relative standard deviations (RSDs) for intra-day and inter-day were less than 4.5% and 6.7% (n=6), respectively. Finally, the analysis method was successfully applied to detect estrogens in sewage and emollient water samples.

A column switching ultrahigh-performance liquid chromatography-tandem mass spectrometry method to determine anandamide and 2-arachidonoylglycerol in plasma samples

This study reports a fast, sensitive, and selective column switching ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method to determine the endocannabinoids (eCBs), anandamide (AEA), and 2-arachidonoylglycerol (2-AG) in plasma samples. This bidimensional system used a restricted access media column (RP-8 ADS, 25 mm × 4 mm × 25 μM) in the first dimension and a core-shell Kinetex C18 (100 mm × 2, 1.7 mm × 1 μM) column in the second dimension, followed by detection in a mass spectrometer triple quadrupole (multiple reactions monitoring mode) operating in the positive mode. RP-8 ADS was used for trace enrichment of eCBs (reverse phase partitioning) and macromolecular matrix size exclusion; the core-shell column was used for the chromatographic separation. The column switching UHPLC-MS/MS method presented a linear range spanning from 0.1 ng mL^-1 (LOQ) to 6 ng mL^-1 for AEA and from 0.04 ng mL^-1 (LOQ) to 10 ng mL^-1 for 2-AG. Excluding the LLOQ values, the precision assays provided coefficients of variation lower than 8% and accuracy with relative standard error values lower than 14%. Neither carryover nor matrix effects were detected. This high-throughput column switching method compared to conventional methods is time saving as it involves fewer steps, consumes less solvent, and presents lower LLOQ. The column switching UHPLC-MS/MS method was successfully applied to determine AEA and 2-AG in plasma samples obtained from Alzheimer's disease patients. Graphical abstract A column switching ultra high-performance liquid chromatography-tandem mass spectrometry method using RP-8 ADS column and core shell column to determine endocannabinoids in plasma samples.

Column switching UHPLC–MS/MS with restricted access material for the determination of CNS drugs in plasma samples

Background: Polypharmacy is a common practice in schizophrenia. Consequently, therapeutic drug monitoring is usually adopted to maintain the concentrations of the drugs in the plasma within a targeted therapeutic range, to maximize therapeutic efficiency and to diminish adverse side effects. Methodology: This study reports on a column switching UHPLC–MS/MS method to determine psychotropic drugs in plasma samples simultaneously. Results: The method was linear from 0.025 to 1.25 ng ml-1 with R2 above 0.9950 and the lack of fit test (p > 0.05). The precision values presented coefficients of variation lower than 12%, and the relative standard error of the accuracy were lower than 14%. Conclusion: The column switching UHPLC–MS/MS method developed herein successfully determined drugs in schizophrenic patients’ plasma samples for therapeutic drug monitoring.