Current advances and applications of in-tube solid-phase microextraction

Promoting capillary microextraction of six organic nitrogen pesticides in water samples using versatile ZIF-8 hybrid monolithic column

Because of rapid industrialization and agriculturalization, solving the pressing problems of environment pollution, especially water and food quality, requires innovative solutions. In this paper, a novel and versatile metal-organic framework (ZIF-8)-hybrid monolithic column (ZIF-HMC) was prepared for in-tube solid-phase microextraction (IT-SPME) of organic nitrogen pesticides (ONPs). The prepared monolithic columns had superior adsorption sites, high porosity, excellent permeability, and ideal specific surface area based on Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Thermal Field Emission Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS), X-ray Photoelectron Spectroscopy (XPS), and N2 adsorption-desorption. The ZIF-HMC contained a large number of nitrogen and oxygen atoms, benzene rings and ZIF-8, which could synergistically promote the adsorption efficiency of ONPs through multiple interactions, such as hydrogen bonding, π-π accumulation, hydrophobic interactions, cation-π interactions, and pore adsorption by MOFs. Under the optimal conditions, a simple, efficient, and sensitive method for the analysis of six organic pesticides in environmental water samples was developed by using the ZIF-HMC as the extraction medium coupled with high performance liquid chromatography-ultraviolet (HPLC-UV). The method had a wide linear range (0.63-1000 μg L-1), a low detection limit (0.19-1.91 μg L-1) and satisfactory recoveries (87.4 %-110.2 %), the linear correlation coefficient was (R2) 0.9972-0.9995 and the relative standard deviation (RSD) was less than 2.64 %. The study had demonstrated the potential application of the developed method for the enrichment and analysis of organic pesticides in complex matrices of environmental samples, as well as the feasibility of MOFs materials for IT-SPME sample preparation.

A comprehensive review of portable syringe systems using micropipette-based extraction techniques for metal analysis

The release of harmful compounds, particularly dangerous metal ions, into the environment has drawn deep concern from the scientific community. Therefore, it has become common in research to evaluate and quantify the harmful concentrations in the presence of these metal ions in several real samples (food, water, and biological samples). To increase sensitivity and lessen the impact of the matrix, sample pretreatment is a helpful strategy to implement before analysis. The limitations of conventional methods have been recently significantly reduced by developing new analytical approaches such as microextraction techniques. The miniaturization of conventional solid-phase extraction (SPE) led to solid-phase microextraction (SPME), drastically reducing both adsorbent use and extraction phase volume. SPME is defined in the present context as a modified extraction technique that employs a portable syringe system attached to micropipette tips. The SPME is considered one of the most appropriate sample preparation tools due to its compatibility with different detection techniques for different metal ions. The current review focuses on SPME based on a portable syringe (attaches to a micropipette tip) system because it has many advantages over conventional solid-phase extraction. It can be designed very simply in a syringe system, a very small quantity of the sorbent has to be kept in the tip, tube, or inside a syringe as a plug and combined with various analytical instruments. Many researchers have designed their own by using homemade tips packed with a sorbent to increase extraction capability and selectivity. According to the current review, there is a lot of potential for increasing the efficacy and efficiency of metal ion extraction from complicated matrices using portable syringe SPME. Studies have shown that when compared to conventional approaches, it performs better in terms of sensitivity, selectivity, and user-friendliness. Furthermore, its application to a wider range of sample types has been enhanced by the flexibility in constructing unique sorbent tips. Conclusively, the developments in portable syringe SPME have addressed several limitations of conventional techniques, positioning it as a robust and versatile tool for environmental monitoring and analysis of hazardous metal ions.

Triazoles in the environment: An update on sample pretreatment and analysis methods

Triazoles, due to their high bactericidal performance, have been widely used in the agricultural, clinical, and chemical industry. However, triazoles have been proven to cause endocrine-toxic and organ impairment in humans as a potentially toxic substance. Besides, because of the improper use and difficulty of degradation, triazoles pesticide residues left in the environment could pose a threat to the environment. Therefore, the rapid, reliable, accurate, and high-sensitivity triazoles analysis methods are significantly essential to effectively monitor their presence in various samples and safeguard human health. This review aims to summarize and update the progress of the pretreatment and analytical methods of triazole fungicides in environmental samples from 2012 to 2024. Common pretreatment methods used to extract and purify targets include simple steps (e.g., protein precipitation and coated blade spray), liquid-liquid extraction, solid-phase extraction, and various microextraction methods such as liquid-phase microextraction and solid-phase microextraction, among others. Detection methods mainly include liquid chromatography-mass spectrometry, gas chromatography-mass spectrometry, supercritical fluid chromatography, sensing methods, and capillary electrophoresis. In addition, we elaborate and compare the advantages and disadvantages of different pretreatment and analytical methods, and their development prospects are discussed.

In-tube solid-phase microextraction of polycyclic aromatic hydrocarbons from refinery water samples using UiO-66/polyacrylonitrile electrospun nanofibers followed by high-performance liquid chromatography-ultraviolet detection

A simple and quick fiber-in-tube solid-phase microextraction (FIT-SPME) was introduced for the extraction and determination of nine polycyclic aromatic hydrocarbons followed by a high-performance liquid chromatography-ultraviolet detector in refinery water samples. For this purpose, a water-resistant metal-organic framework with a high surface area called UiO-66 has been applied in the form of an electrospun coating on stainless steel wires. After that, all the fibers were packed in the lumen of a stainless-steel tube to make the extraction phase. Both one variable at a time and experimental design methods have been used to optimize effective parameters on FIT-SPME. Under optimum conditions, the method demonstrated good linearity between 0.5 and 1000.0 µg/L with a coefficient of determination greater than 0.9906. Furthermore, the limits of detection values ranged from 0.2 to 1.5 µg/L. The intra-day and inter-day relative standard deviations were < 8.4% and < 9.7%, respectively. Lastly, the proposed method was applied to extract and determine analytes in four refinery water samples as well as surface water containing high total dissolved solids, and well waters where satisfactory results have been obtained.

Recent advances in solid phase microextraction with various geometries in environmental analysis

Solid phase microextraction (SPME) has emerged as a versatile sample preparation technique for the preconcentration of a broad range of compounds with various polarities, especially in environmental studies. SPME has demonstrated its eco-friendly credentials, significantly reducing the reliance on solvents. The use of biocompatible materials as a coating recipe facilitates the acceptance of SPME devices in analytical chemistry, primarily in the monitoring of environmental pollutants such as persistent organic pollutants (POPs), volatile organic compounds (VOCs), and pesticides from the various environmental matrices. During the last few years, investigators have reported an improvement in the SPME enrichment technique after changing the coating recipe, geometries, and sampling procedure from the complex matrices. Furthermore, the development of various geometries of SPME with large surface areas has enhanced the extraction efficiency of environmental pollutants. As a miniaturized sample preparation technique, SPME significantly reduces the solvent usage, suggesting a potential platform for green chemistry-based research for water, air, and soil analysis. This review article summarizes the evolution of SPME, its various modes, the application of SPME, recent innovations, and prospects for the determination of water, air, and soil pollution. The advantages and disadvantages of SPME in comparison to other extraction techniques have been discussed here. This review serves as a valuable resource for investigators working in sustainable environmental research.

Microextraction techniques for occupational biological monitoring: Basic principles, current applications and future perspectives

The application of green microextraction techniques (METs) is constantly being developed in different areas including pharmaceutical, forensic, food and environmental analysis. However, they are less used in biological monitoring of workers in occupational settings. Developing valid extraction methods and analytical techniques for the determination of occupational indicators plays a critical role in the management of workers' exposure to chemicals in workplaces. Microextraction techniques have become increasingly important because they are inexpensive, robust and environmentally friendly. This study aimed to provide a comprehensive review and interpret the applications of METs and novel sorbents and liquids in biological monitoring. Future perspectives and occupational indicators that METs have not yet been developed for are also discussed.

Organic-silica hybrid monolithic sorbents for sample preparation techniques: A review on advances in synthesis, characterization, and applications

Organic-silica hybrid monolithic materials have attracted considerable attention as potential stationary phases in separation science. These materials combine the advantages of organic polymer and silica-based monoliths, including easy preparation, lower back pressure, high permeability, excellent mechanical strength, thermal stability, and tunable surface chemistry with high surface area and selectivity. The outstanding chromatographic efficiency as stationary phase of hybrid monolithic capillary columns for capillary liquid chromatography and capillary electrochromatography has been reported in many papers. Organic-silica hybrid monolithic materials have also been extensively used in the field of sample preparation. Owing to their surface functionalities, these porous sorbents offer unique selectivity for pre-concentration of different analytes in the most complex matrixes by fast dynamic transport. These sorbents not only improve the analytical method sensitivity, but also introduce novelties in terms of extraction devices and instrument coupling strategies. The current review covers the period spanning from 2017 to 2023 and describes the properties of organic-inorganic hybrid monolithic materials, the present status of this technology and summarizes recent developments in their use as innovative sorbents for microextraction sample preparation techniques (solid phase microextraction with pipette tip, offline in-tube SPME, in-tube SPME online with LC, and in-tube SPME directly coupled with mass spectrometry). Aspects such as the synthesis methods (sol-gel process, one-pot approach, and polyhedral oligomeric silsesquioxanes-based procedure), characterization techniques, and strategies to improve extraction efficiency in various applications in different areas (environmental, food, bioanalysis, and proteomics) are also discussed.

Multivariate surface self-assembly strategy to fabricate ionic covalent organic framework surface grafting monolithic sorbent for enrichment of aristolochic acids prior to high performance liquid chromatography analysis

Herein, an ionic covalent organic framework (iCOF) surface grafting monolithic sorbent was prepared by the multivariate surface self-assembly strategy for in-tube solid-phase microextraction (SPME) of trace aristolochic acids (AAs) in serum, traditional Chinese medicines (TCMs) and Chinese patent drug. Via adjusting the proportion of ionic COF building block during the self-assembly, the density of quaternary ammonium ions in the iCOF was modulated for the enhanced adsorption of AAs. The successful preparation of iCOF surface grafting monolithic sorbent was confirmed by different means. A multiple mode mechanism involving π-π stacking, hydrophobic, electrostatic and hydrogen-bonding interactions was primarily attributed to the adsorption. Several in-tube SPME operating conditions, such as the dosage of ionic COF building block, ACN percentage and TFA percentage in the sampling solution, ACN percentage and TFA percentage in eluent and the collection time span, were optimized to develop the online in-tube SPME-HPLC method for analysis of AAs. Under the optimized conditions, a good linearity was obtained in the concentration range of 20-1000 ng/mL for target AAs in serum samples, the limits of detection (LODs) were less than 10 ng/mL, while the recoveries ranged from 90.3 % to 98.7 % with RSDs (n = 5) below 7.9 %. This study developed a feasible approach to iCOF functionalized monolithic sorbent for SPME and further exhibited the vast potential for the application of COF based monolithic sorbent in sample preparation.

Vortex-assisted microextraction of melamine from milk samples using green short chain ionic liquid solvents coupled with high performance liquid chromatography determination

Melamine is added illegally to milk and dairy products to increase the amount of apparent protein. This organic nitrogen rich chemical compound has been of great challenge in food safety based on its adverse effect on health. Therefore, the extraction and determination of melamine from milk is necessary. Recently, ionic liquid (ILs) as solvent usage has been noticeable for low melting point, low toxicity, high thermal stability, and high extraction capabilities in a wide range of separation processes. ILs are introduced as organic-inorganic salts and green solvents in microextraction preparation. Therefore, in this study, three ionic liquids ([C6mim][NTF2], [C4mim][NTF2] and [C2mim][NTF2] ILs) were prepared and employed as an extraction solvent in dispersive liquid-liquid microextraction (DLLME) of melamine from milk samples followed by HPLC-UV. The selected ILs were designed using three types of alkyl-imidazolium (as the short organic cations) and bis (tri fluoro methyl sulfonyl) imide as anion and characterized by ATR-FTIR spectra, carbon, and hydrogen Nuclear Magnetic Resonance spectroscopy (H&C-NMR) and energy-dispersive X-ray spectroscopy (EDX). These techniques confirmed the formation of functional groups, the structure of hydrogen and carbon atoms, and various elements of ionic bond between imidazolium and bis (tri fluoro methyl sulfonyl) imide. In the next step, the effect of significant parameters, including type and volume of ILs, adsorption time, pH of the sample solution, and sample volume, were optimized. Under the optimal conditions, the limits of detection (LOD), limits of quantification (LOQ), and linearity range were obtained 63.64 µg kg-1, 210.03 µg kg-1, and 210.03-1000 µg kg-1, respectively, for as prepared [C6mim][NTF2] as the best ILs. Notably, the achieved LOQ was lower than the maximum residue level (MRL) for the melamine residue in dairy products. Eventually, the proposed method was applied to detect melamine in milk samples, and the relative recoveries were examined as 79.6-105.0 %.

Open tubular liquid chromatography: Recent advances and future trends

Nano-liquid chromatography (nanoLC) is gaining significant attention as a primary analytical technique across various scientific domains. Unlike conventional high-performance LC, nanoLC utilizes columns with inner diameters (i.ds.) usually ranging from 10 to 150 μm and operates at mobile phase flow rates between 10 and 1000 nl/min, offering improved chromatographic performance and detectability. Currently, most exploration of nanoLC has focused on particle-packed columns. Although open tubular LC (OTLC) can provide superior performance, optimized OTLC columns require very narrow i.ds. (< 10 μm) and demand challenging instrumentation. At the moment, these challenges have limited the success of OTLC. Nevertheless, remarkable progress has been made in developing and utilizing OTLC systems featuring narrow columns (< 2 μm). Additionally, significant efforts have been made to explore larger columns (10-75 μm i.d), demonstrating practical applicability in many situations. Due to their perceived advantages, interest in OTLC has resurged in the last two decades. This review provides an updated outlook on the latest developments in OTLC, focusing on instrumental challenges, achievements, and advancements in column technology. Moreover, it outlines selected applications that illustrate the potential of OTLC for performing targeted and untargeted studies.

Applicability and Limitations of a Capillary-LC Column-Switching System Using Hybrid Graphene-Based Stationary Phases

Graphene oxide sheets fixed over silica particles (SiGO) and their modification functionalized with C18 and endcapped (SiGO-C18ec) have been reported as sorbents for extraction and analytical columns in LC. In this study, a SiGO column was selected as the extraction column and a SiGO-C18ec as the analytical column to study the applicability and limitations of a column-switching system composed exclusively of columns packed with graphene-based sorbents. Pyriproxyfen and abamectin B1a were selected as the analytes, and orange-flavored carbonated soft drinks as the matrix. The proposed system could be successfully applied to the pyriproxyfen analysis in a concentration range between 0.5 to 25 µg/mL presenting a linearity of R² = 0.9931 and an intra-day and inter-day accuracy of 82.2-111.4% (RSD < 13.3%) and 95.5-99.8% (RSD < 12.7%), respectively. Furthermore, the matrix composition affected the area observed for the pyriproxyfen: the higher the concentration of orange juice in the soft drink, the higher the pyriproxyfen the signal observed. Additionally, the SiGO extraction column presented a life use of 120 injections for this matrix. In contrast, the proposed system could not apply to the analysis of abamectin B1a, and the SiGO-C18ec analytical column presented significant tailing compared to a similar approach with a C18 analytical column.

Ionic liquid assisted in situ growth of nano-confined ionic liquids/metal-organic frameworks nanocomposites for monolithic capillary microextraction of microcystins in environmental waters

A facile in-situ ionothermal synthesis strategy for fabrication of ionic liquids/metal-organic frameworks (MOFs) (ILs@ZIF-8) nanocomposites hybrid monolith has been proposed to facilitate highly effective capillary microextraction (CME) of ultra-trace microcystins (MCs) in environmental waters. The ZnO nanoparticles (ZnO-NPs) were initially introduced into a precursor polymer monolith, and acted as the metal sources and anchoring seeds to construct ILs@ZIF-8 nanocomposites hybrid monolith via a nanoparticle-directed in-situ growth route in confined imidazolium ionic liquids. Detailed characterization based on scanning electron microscopy (SEM), X-ray diffraction (XRD) and N₂ adsorption-desorption isotherms confirmed that both the morphology and porous structure of ZIF-8 were finely tuned by the incorporation of ILs, which acted as solvents and structure directing agent. The confinement of ILs in ZIF-8 framework endows the ILs@ZIF-8 hybrid monolith additional adsorption sites and satisfied water stability for the synergistic enhancement of adsorption efficiency of MCs via multiple interactions (including π-π stacking, hydrogen bonding, hydrophobic and electrostatic interactions). Coupling ILs@ZIF-8 hybrid monolith-based CME to LC-MS enabled an efficient and sensitive analysis of MCs in surface waters with ultra-low detection limits (LOD ≤ 1.4 ng L^-1) and satisfactory recoveries (70.2%-107.0%). This study showed great potential for feasible design and fabrication of ILs@MOFs composites with synergistic and tunable structures toward efficient sample preparation applications.

Direct coupling in-tube solid-phase microextraction with mass spectrometry using polymer coated open-tubular column for rapid analysis of antiepileptic drugs in biofluids

Development of high-throughput and rapid screening analytical method is in high demand for anti-doping and clinical point-of-care (POC) analysis. Solid-phase microextraction and mass spectrometry direct coupling (SPME-MS) has been proved as a rapid and effective way for target analysis in complex sample matrixes. An online direct coupling of in-tube SPME (IT-SPME) with MS using polymer coated open-tubular column has been developed in this work. A sharp stainless-steel needle was attached at the end of the SPME column, which enables the direct ionization of the analytes after elution from the IT-SPME column. Itaconic acid-benzene co-polymer was in-situ grown on the inner surface of the fused silica capillary and used as extraction phase. This column has low backpressure and provides both hydrophobic and weak cationic exchange interaction with the target analytes due to the chemical properties. The developed online IT-SPME-MS method showed good extraction performance towards various target analytes and good reusability at least for 60 times. As a proof-of-concept application, the above method was applied for the analysis of antiepileptic drugs (AEDs) in both plasma and urine samples with linear range (1 ng/mL-200 ng/mL), good linearity (R² ≥ 0.99), and good reproducibility (intra-day RSDs less than 4.36%, inter-day RSDs less than 6.55%). The method exhibited high enrichment factors between 187 and 204 for the two AEDs and high sensitivity for the analysis of human plasma samples and urine samples.

Online Extraction Followed by LC-MS/MS Analysis of Lipids in Natural Samples: A Proof-of-Concept Profiling Lecithin in Seeds

Sample preparation is usually a complex and time-consuming procedure, which can directly affect the quality of the analysis. Recent efforts have been made to establish analytical methods involving minimal sample preparation, automatized and performed online with the analytical techniques. Online Extraction coupled with Liquid Chromatography-Mass Spectrometry (OLE-LC-MS) allows a fully connected extraction, separation, and analysis system. In this work, the lecithin profile was investigated in commercial sunflower, almonds, peanuts, and pistachio seeds to demonstrate that the concept of extraction, followed by the online analysis of the extract, could be applied to analyze this class of analytes in such complex solid matrices without a prior off-line solvent extraction step. The extraction phase gradient method was optimized. Two different analytical columns were explored, one being a conventional C18 (50 × 2.1 mm, 1.7 µm SPP) and the other a novel self-packed SIGO-C18ec (100 × 0.5, 5 µm FPP), which resulted in better separation. The analysis repeatability was investigated, and suggestions to improve it were pointed out. A characteristic ion with a m/z of 184, related to lysophosphatidylcholine structure, was used to identify the lecithin compounds. The temperature effect on the chromatograms was also explored. In short, it was found that the OLE-LC-MS approach is suitable for the analysis of lecithin compounds in seeds, being a promising alternative for lipidomics approaches in the near future.

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.

A New Trend and Future Perspectives of the Miniaturization of Conventional Extraction Methods for Elemental Analysis in Different Real Samples: A Review

Sample preparation is one of the viable procedures to be used before analysis to enhance sensitivity and reduce the matrix effect. The current review is mainly emphasized the latest outcome and applications of microextraction techniques based on the miniaturization of the classical conventional methods based on liquid-phase and solid-phase extraction for the quantitative elemental analysis in different real samples. The limitation of the conventional sample preparation methods (liquid and solid phase extraction) has been overcome by developing a new way of reducing size as compared with the conventional system through the miniaturization approach. Miniaturization of the sample preparation techniques has received extensive attention due to its extraction at microlevels, speedy, economical, eco-friendly, and high extraction capability. The growing demand for speedy, economically feasible, and environmentally sound analytical approaches is the main intention to upgrade the conventional procedures apply for sample preparation in environmental investigation. A growing trend of research has been perceived to quantify the trace for elemental analysis in different natures of real samples. This review also recapitulates the current futuristic scenarios for the green and economically viable procedure with special overemphasis and concentrates on eco-friendly miniaturized sample-preparation techniques such as liquid-phase microextraction (LPME) and solid-phase microextraction (SPME). This review also emphasizes the latest progress and applications of the LPME and SPME approach and their future perspective.

Recent applications of organic molecule-based framework porous materials in solid-phase microextraction for pharmaceutical analysis

Sample preparation is an indispensable part of detection of complex samples in pharmaceutical analysis. Solid-phase microextraction (SPME) has obtained a lot of attention due to its advantages of time saving, less solvent and easily automation. A variety of functional materials are used as sorbents in SPME to carry out selective and high extraction. This review centers around the recent applications of organic molecule-based framework porous materials, such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs), as SPME coating materials mainly focus on pharmaceutical analysis in food, environment, and biological samples. Four representative extraction devices are introduced, including on-fiber SPME, in-tube SPME, thin film SPME, stir bar SPME. The application prospect of other organic porous materials as sorbents for pharmaceutical analysis are also discussed, such as hyper crosslinked polymers (HCPs) and conjugated microporous polymers (CMPs). The progresses and discusses are provided to offer references for further research focusing on application and development of organic molecule-based framework porous materials in the field of SPME.

Functionalized monolithic columns: Recent advancements and their applications for high-efficiency separation and enrichment in food and medicine

The chromatographic column is the core of a high-performance liquid chromatography (HPLC) system, and must have excellent separation efficiency and selectivity. Therefore, functional modification materials for monolithic columns have been rapidly developed. This study is a systematic review of the recently reported functionalized monolithic columns. In particular, the study reviews the types of functional monomers under different modification conditions, as well as the separation and detection techniques combined with chromatography, and their development prospects. In addition, the applications of functionalized monolithic columns in food analysis, biomedicine, and the analysis of active ingredient of Chinese herbal medicines in recent years are also discussed. Also reviewed are the functionalized monolithic columns for qualitative and quantitative analysis. It provided a reference for further development and application of organic polymer monolithic columns.

Environmentally friendly analysis of sulphonamides in Brazilian honey through automated and miniaturised sample preparation coupled with LC-MS/MS

Increased use of environmentally friendly practices has become a trend in science because of the current awareness regarding climate change and related issues. Similarly for analytical chemistry, considering the development of greener methods for reducing the use of reagents and samples and also toxic waste generation. To meet such goals, automation, and miniaturisation of sample preparation-a well-recognised laborious and time-consuming analytical step-are two promising strategies. This work associates the greener aspects of miniaturisation and the performance of automated sample preparation. Therefore, we proposed an analytical method using a miniaturised extraction column for pre-concentrating sulphamerazine, sulphamethazine, sulphamethoxazole, sulphadimethoxine, sulphathiazole, and sulphachlorpyridazine from honey and cleaning-up the samples. Several variables were optimised: extractive phase, loading flow, loading phase, and loading time. Under optimised conditions, the method showed adequate linearity between 5.0 and 60 ng g^-1 with R > 0.99, and also good selectivity and recovery (114.6-124.1%) which are acceptable according to Brazilian legislation. Intra and inter-day precision were in the range 3.0-5.0%. Although sulphonamides were detected in one of the eight commercial honey samples, the value was below the established MRL. The method showed efficiency, while also exhibiting greener characteristics resulting from miniaturisation and automation, representing a promising environmentally friendly alternative for conventional sample preparation methods.

A cartridge-based device for automated analyses of solid matrices by online sample prep-capillary LC-MS/MS

Sample preparation is an essential step focused on eliminating interfering compounds while pre-concentrating the analytes. However, its multiple steps are laborious, time-consuming, and a source of errors. Currently, automated approaches represent a promising alternative to overcome these drawbacks. Similarly, miniaturisation has been considered an ideal strategy for creating greener analytical workflows. The combination of these concepts is currently highly desired by analytical chemists. However, most automated and miniaturised sample preparation techniques are primarily concerned with liquid samples, while solids are frequently overlooked. We present an approach based on a cartridge packed with solids (soil samples) coupled with a capillary LC-MS, combining sample preparation and analytical steps into a unique platform. As a proof-of-concept, nine pesticides used in sugarcane crops were extracted and analysed by our proposed method. For optimisation, a fractional factorial design (2^5-1) was performed with the following variables: aqueous dilution of the sample (V₁), extraction strength (V₂), matrix washing time (V₃), extraction flow (V₄), and analytical flow (V₅). After, the most influential ones (V₁, V₂, and V₃) were taken into a central composite design (2³) to select their best values. Under optimised conditions, the method reported linear ranges between 10 and 125 ng g^-1 with R² > 0.985. Accuracy and precision were in accordance with the values established by the International Council for Harmonisation (Q2(R1)). Therefore, the proposed approach was effective in extracting and analysing selected pesticides in soil samples. Also, we carried out initial qualitative tests for pesticides in honeybees to see if there is the possibility to apply our method in other solids.

Portable paper-in-tip spray ionization for the direct mass spectrometric analysis of target analytes in biofluid samples

Portable sampling of target analytes in complex biofluid samples makes mass spectrometric analysis more efficient. This study reports the development of paper-in-tip spray ionization for solid-phase microextraction and in situ electrospray of therapeutic drugs and proteins in complex biological matrices using a piece of hydrophobic paper substrate. This technique possesses a long (more than 8 min) and stable spray duration with only 20 μL of spray solvent. The entire analytical process for a complex sample can be completed in less than 1.5 min and enables high sensitivity (picogram-per-milliliter level) and high quantitation precision.

A novel polyhedral oligomeric silsesquioxane-based hybrid monolith as a sorbent for on-line in-tube solid phase microextraction of bisphenols in milk prior to high performance liquid chromatography-ultraviolet detection analysis

An on-line in-tube solid-phase microextraction (in-tube SPME) coupled with high-performance liquid chromatography (HPLC) method was proposed based on a novel polyhedral oligomeric silsesquioxane (POSS)-hybrid monolith for the determination of four bisphenols (BPs) in milk. The monolith was synthesized using acrylamide (AM) and monomethacrylate-functionalized POSS (mono-MA-POSS) as functional monomers to copolymerize with ethylene dimethacrylate (EDMA). Due to the abundant hydrogen bonding, π-π and hydrophobic interaction sites, the synthetic monolith displayed satisfying extraction performance for target BPs. Under the optimized conditions, the developed on-line in-tube SPME-HPLC method exhibited low limits of detection (LODs) (0.030-0.055 ng mL^-1). The spiked recoveries were between 85.4 % and 111.8 %, and the relative standard deviations (RSDs) were less than 3.5 % for all the analytes. The results showed that the proposed method provided alternative for the analysis of BPs in complex samples.

Recent advances in porous organic frameworks for sample pretreatment of pesticide and veterinary drug residues: a review

Rapid and accurate detection of pesticide and veterinary drug residues is a continuing challenge because of the complex matrix effects. Thus, appropriate sample pretreatment is a crucial step for the effective extraction of the analytes and removal of the interferences. Recently, the development of nanomaterial adsorbents has greatly promoted the innovation of food sample pretreatment approaches. Porous organic frameworks (POFs), including polymers of intrinsic microporosity, covalent organic frameworks, hyper crosslinked polymers, conjugated microporous polymers, and porous aromatic frameworks, have been widely utilized due to their tailorable skeletons and pores as well as fascinating features. This review summarizes the recent advances for POFs to be utilized in adsorption and sample preparation of pesticide and veterinary drug residues. In addition, future prospects and challenges are discussed, hoping to offer a reference for further study on POFs in sample pretreatment.

Molecularly imprinted polypyrrole@CuO nanocomposite as an in-tube solid-phase microextraction coating for selective extraction of carbamazepine from biological samples

A nanocomposite of molecularly imprinted polypyrrole on copper oxide (MIP@CuO) was introduced as a new coating for in-tube solid-phase microextraction (IT-SPME). The method coupled with HPLC-UV was successfully applied for analysis of carbamazepine (anticonvulsant and bipolar disorder medication) in biological samples. First, in order to increase the surface area and stability of the coating, copper oxide (CuO) nanosheets were synthesized on the inner surface of a copper tube using a chemical method. Then, molecularly imprinted polypyrrole coating (using carbamazepine as a template) was deposited on CuO by a facile in-situ electrodeposition method. According to the results, The MIP@CuO coating shows long life time, enhanced extraction efficiency, and good clean-up, for pre-concentration and determination of carbamazepine in biological samples. The synthesized adsorbent also showed high selectivity to carbamazepine compared to other drugs with similar structure. Important factors affecting the extraction efficiency of the analyte in the in-tube SPME method, such as salt concentration, extraction and desorption times, flowrates of the sample solution, and eluent, were optimized. Under optimal conditions, the method showed good linearity for carbamazepine in the range of 0.05-500 μg L^-1, 0.10-500 μg L^-1, and 0.10-500 μg L^-1 in water, urine, and plasma samples, respectively, with coefficients of determination better than 0.996. The limits of detection were in the range of 0.01-0.05 μg L^-1 in different matrices. The intra- and inter-assay precisions (RSD%, n = 3) were in the range of 6.7-8.1 % and 7.1-9.5 %, respectively.

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.

Biomass-derived carbon nanospheres decorated by manganese oxide nanosheets, intercalated into polypyrrole, as an inside-needle capillary adsorption trap sorbent for the analysis of linear alkylbenzenes

Carbon nanospheres (CNSs) were derived hydrothermally from biomass (orange peels) and decorated by manganese dioxide (MnO₂) nanosheets. The MnO₂/CNSs nanocomposite was intercalated into polypyrrole (PPy) during flow-through in-situ electropolymerization of pyrrole on the surface of the inner wall of a stainless-steel needle to prepare an inside-needle capillary adsorption trap (INCAT) device. The surface morphology, thermogravimetric behavior, sorption characteristics, and structure of the MnO₂/CNSs@PPy nanocomposite were characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), nitrogen physisorption by the Brunauer-Emmett-Teller (BET) method, dynamic light scattering (DLS) size distribution, and Fourier-transform infrared spectrometry (FT-IR). The INCAT device was coupled with GC-FID and applied for dynamic headspace analysis of linear alkyl benzenes (LABs) in wastewater samples. The effective experimental variables on the extraction efficiency was optimized using a central composite design (CCD) based on response surface methodology (RSM). Under the optimal conditions, the limits of detection (LODs) were in the range of 0.5-1.0 ng mL^-1. The calibration plots were linear over the range of 0.01-10 μg mL^-1. The relative standard deviations (RSDs%) for intra-day, inter-day, and inter-INCAT precision were calculated 5.3-8.3%, 9.4-13.5%, and 13.6-16.9%, respectively. The developed technique was employed successfully for the analysis of LABs in water and wastewater samples with average recovery values ranging from 92 to 109%. A single INCAT device was used more than 90 times without significant change in its extraction capability.

Nanoplatform-Integrated Miniaturized Solid-Phase Extraction Techniques: A Critical Review

Preparation of the biological samples is one of the most critical steps in sample analysis. In past decades, the liquid-liquid extraction technique has been used to extract the desired analytes from complex biological matrices. However, solid-phase extraction (SPE) gained popularity due to versatility, simplicity, selectivity, reproducibility, high sample recovery %, solvent economy, and time-saving nature. The superior extraction efficiency of SPE can be attributed to the development of advanced techniques, including the nanosorbents technology. The nanosorbent technology significantly simplified the sample preparation, improved the selectivity, diversified the application, and accelerated the sample analysis. This review critically expands on the to-date advancements reported in SPE with particular regards to the nanosorbent technology.

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.

Application of magnetic nanomaterials in magnetic in-tube solid-phase microextraction

Development of magnetic nanomaterials has greatly promoted the innovation of in-tube solid-phase microextraction. This review article gives an insight into recent advances in the modifications and applications of magnetic nanomaterials for in-tube solid-phase microextraction. Also, different magnetic nanomaterials which have recently been utilized as in-tube solid-phase microextraction sorbents are classified. This study shows that magnetic nanomaterials have gained significant attention owing to large specific surface area, selective absorption, and surface modification. Magnetic in-tube solid-phase microextraction has been applied for the analysis of food samples, biological, and environmental. However, for full development of magnetic in-tube SPME, effort is still needed to overcome limitations, such as mechanical stability, selectivity and low extraction efficiency. To achieve these objectives, research on magnetic in-tube SPME is mainly focused in the preparation of new extractive phases.

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.

In-tube solid-phase microextraction directly coupled to tandem mass spectrometry for anandamide and 2-arachidonoylglycerol determination in rat brain samples from an animal model of Parkinson's disease

To evaluate the endocannabinoid system in an animal model of Parkinson's disease, in-tube solid-phase microextraction (in-tube SPME) was directly coupled to a tandem mass spectrometry (MS/MS) system for determination of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) in rat brain samples. In-tube SPME-which consisted of a microtube of restricted access material (RAM) with a hydrophilic diol external surface and a hydrophobic octyl inner surface-efficiently excluded (up to 95%) macromolecules from the biological samples and selectively pre-concentrated the analytes. In-tube SPME parameters, such as sample volume, mobile phases, flow rate, and pre-concentration time, were evaluated to improve the extraction efficiency and throughput performance. The selectivity of the in-tube SPME and MS/MS (MRM mode) techniques allowed them to be directly coupled online, which dismissed the need for the chromatographic separation step. The in-tube SPME-MS/MS method was validated and shown to be linear from 6.0 to 30.0 ng mL^-1 for AEA and from 10.0 to 100.0 ng mL^-1 for 2-AG; the intra- and inter-assay accuracy and precision were lower than 15%. Parallelism between the calibration curves constructed in the matrix and aqueous solution confirmed that there was no matrix effect. The method allowed endogenous concentrations of AEA and 2-AG to be determined in rat brain striatum from unilaterally 6-hydroxydopamine-lesioned animals. The concentrations of these endocannabinoids in striatum ipsilateral and contralateral to the lesion differed significantly (p<0.001).

Miniaturized analytical methods for determination of environmental contaminants of emerging concern - A review

The determination of contaminants of emerging concern (CECs) in environmental samples has become a challenging and critical issue. The present work focuses on miniaturized analytical strategies reported in the literature for the determination of CECs. The first part of the review provides brief overview of CECs whose monitoring in environmental samples is of particular significance, namely personal care products, pharmaceuticals, endocrine disruptors, UV-filters, newly registered pesticides, illicit drugs, disinfection by-products, surfactants, high technology rare earth elements, and engineered nanomaterials. Besides, an overview of downsized sample preparation approaches reported in the literature for the determination of CECs in environmental samples is provided. Particularly, analytical methodologies involving microextraction approaches used for the enrichment of CECs are discussed. Both solid phase- and liquid phase-based microextraction techniques are highlighted devoting special attention to recently reported approaches. Special emphasis is placed on newly developed materials used for extraction purposes in microextraction techniques. In addition, recent contributions involving miniaturized analytical flow techniques for the determination of CECs are discussed. Besides, the strengths, weaknesses, opportunities and threats of point of need and portable devices have been identified and critically compared with chromatographic methods coupled to mass chromatography. Finally, challenging aspects regarding miniaturized analytical methods for determination of CECs are critically discussed.