In-tube Solid-phase Microextraction Research Articles

Determination of Luteolin and Apigenin in Herbal Teas by Online In-Tube Solid-Phase Microextraction Coupled with LC–MS/MS

Herbal teas have attracted attention as functional beverages containing luteolin and apigenin, which exhibit antioxidant and anti-inflammatory effects. The objective of this study was to develop a sensitive online automated method to determine these flavones’ contents in herbal teas using in-tube solid-phase microextraction (IT-SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS). These compounds were extracted and concentrated by IT-SPME using a Supel Q PLOT capillary column and then separated and detected within 6 min using a CAPCELL PAK C18 MG III analytical column and a negative electrospray ionization-mode multiple-reaction monitoring system by LC–MS/MS. The detection limits (S/N = 3) for luteolin and apigenin were 0.4 and 0.8 pg mL−1, respectively, and the calibration curves were linear in the range of 2–2000 pg mL−1 with correlation coefficients above 0.9995, and intra-day and inter-day precisions with relative standard deviations below 2.9 and 3.6% (n = 6), respectively. The luteolin and apigenin in herbal tea were quantified using IT-SPME/LC-MS/MS following the acid hydrolysis of their glycosides. Among the 10 herbal teas tested, luteolin was detected in peppermint and sage at concentrations of 375 and 99 µg mL−1, respectively, while apigenin was detected in German chamomile at 110 µg mL−1, which were higher than in the other herbal teas. The method is expected to be a useful method for evaluating the efficacy of luteolin and apigenin in herbal teas as functional beverages.

Enhancing the efficiency of polypyrrole-dodecylbenzene sulfonic acid in-tube solid-phase microextraction coating for analysis of nitrogen-containing pesticides in water environments

Background: With the growing use of nitrogen-containing pesticides in agriculture, their residues in the environment have raised significant public health concerns.Objective: This study aimed to develop a novel PPy-DBSA/IT-SPME coating to enhance the detection efficiency of polar nitrogen-containing pesticides in water matrices.Methods: The preparation conditions were optimized, including pyrrole concentration at 7.0 mol/L, DBSA concentration at 0.014 mol/L, oxidant concentration at 0.35 mol/L, and a coating cycle repeated 10 times. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was employed for detection.Results: The novel coating effectively adsorbed 19 different categories of polar nitrogen-containing pesticides, including sulfonylureas, triazolopyrimidines, diphenyl ether herbicides, benzoylurea insecticides, and phenylurea herbicides, with unadsorbed rates below 10%. The analytical method achieved an average recovery rate of 61.92% to 115.21%, with an RSD below 5.0%. Detection and quantification limits ranged from 0.012 to 0.524 μg/L and 0.127 to 5.243 μg/L, respectively.Conclusion: The developed method is green, efficient, simple, and cost-effective. It offers an environmentally friendly and user-friendly approach for the detection of polar nitrogen-containing pesticide residues, demonstrating good recovery and precision. This method holds potential for wide application in environmental monitoring and food safety.

Development of Noninvasive Method for the Automated Analysis of Nine Steroid Hormones in Human Saliva by Online Coupling of In-Tube Solid-Phase Microextraction with Liquid Chromatography–Tandem Mass Spectrometry

Accurate measurement of steroid hormones is crucial to elucidate new mechanisms of action and diagnose steroid metabolism-related diseases. This study presents a simple, sensitive, and automated analytical method for nine representative steroid hormones. The method involves on-line coupling of in-tube solid-phase microextraction (IT-SPME) with liquid chromatography–tandem mass spectrometry (LC–MS/MS). The steroid hormones were extracted and enriched on a Supel-Q PLOT capillary column using IT-SPME. Subsequently, they were separated and detected within 6 min using a Discovery HS F5-3 column and positive ion mode multiple reaction monitoring system via LC–MS/MS. Calibration curves of these compounds using each stable isotope-labeled internal standard (IS) showed linearity with correlation coefficients greater than 0.9990 in the range of 0.01–40 ng/mL, with limits of detection (S/N = 3) of 0.7–21 pg/mL. Moreover, intra- and inter-day variations were lower than 8.1 and 15% (n = 6), respectively. The recoveries of these compounds from saliva samples were in the range of 82–114%. The developed IT-SPME/LC–MS/MS method of steroid hormones is a highly sensitive, specific, and non-invasive analytical method that allows extraction and enrichment with no organic solvents, and enables direct automated online analysis by simply ultrafiltrating a small sample of saliva.

Aptamer based hybrid monolithic pipette tips supported by melamine sponge for enrichment of proteins

BackgroundThe convenient preparation and application of functionalized organic-inorganic hybrid monolithic materials have obtained substantial interest in the pretreatment of complex samples by solid-phase extraction (SPE). Compared to the in-tube solid-phase microextraction in fused-silica capillaries, micro SPE in plastic pipette tips have fascinating merits for the easily operated enrichment of trace target analytes from biological samples. However, the poor compatibility of organic-inorganic hybrid monoliths with plastics leads to the rare appearance of commercial hybrid monolithic pipette tips (HMPTs). Therefore, how to synthesize the organic-inorganic hybrid monolithic materials with better extraction performance in plastic pipette tips becomes a challenge. ResultsWe develop a facile and cheap strategy to immobilize organic-inorganic hybrid monoliths in pipette tips. Melamine sponge was employed as the supporting skeleton to in situ assemble amine- and thiol-bifunctionalized hybrid monolithic material via “one pot” in a pipette tip, and gold nanoparticles (GNPs) and thiol-modified aptamer against human α-thrombin were sequentially attached to the hybrid monolith within the HMPTs. The average coverage density of the aptamer with GNPs as an intermediary reached as high as 818.5 pmol μL−1. The enriched thrombin concentration was determined by a sensitive enzymatic chromogenic assay with the limit of detection of 2 nM. The extraction recovery of thrombin at 10 nM in human serum was 86.1 % with a relative standard deviation of 6.1 %. This proposed protocol has been applied to the enrichment and determination of thrombin in real serum sample with strong anti-interference ability, low limit of detection and high recovery. SignificanceThe amine- and thiol-bifunctionalized HMPTs prepared with sponge as the skeleton frame provided a novel substrate material to decorate aptamers for efficient enrichment of proteins. This enlightens us that we can take advantage of the tunability of sponge assisted HMPTs to produce and tailor a variety of micro SPE pipette tips for broader applications on the analysis of trace targets in complex biological, clinic and environmental samples.

Silver nanoparticle-functionalized melamine-formaldehyde aerogel for online in-tube solid-phase microextraction of polycyclic aromatic hydrocarbons followed by HPLC-DAD analysis

Based on the π-metal interaction between silver nanoparticles (AgNPs) and aromatic compounds, AgNPs were in-situ grown to melamine-formaldehyde (MF) aerogel for improving the extraction performance to polycyclic aromatic hydrocarbons (PAHs). The AgNPs/MF aerogel was regulated through varing the concentration of reactants, and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray powder diffraction. As a new extraction coating, the AgNPs/MF aerogel was coated to stainless-steel wires for in-tube solid-phase microextraction (IT-SPME). The extraction effects of MF aerogels before and after the modification of AgNPs were compared, and the AgNPs greatly improved the extraction ability for PAHs reaching to 166.4 %. Combining IT-SPME with high performance liquid chromatographic detection, an online analytical system was constructed. Furthermore, the sampling volume and rate, concentration of organic solvent, and desorption time were optimized factor by factor. The online analytical method with low detection limits (0.003–0.010 μg L−1) and efficient enrichment factors (1998–3237) for PAHs was established, which fastly detected trace level of PAHs in drinking and environmental water samples. Compared with other methods, the method was comparable or better in the detection limit and linear range, indicating prospective application of the AgNPs/MF aerogel for sample preparation.

A novel monolithic Zn/Cr-LDH composite for in-tube solid-phase microextraction of acidic herbicides from water samples

A monolithic composite based on Zn/Cr-layer double hydroxide (Zn/Cr-LDH) was introduced for in-tube solid-phase microextraction (IT-SPME) of chlorophenoxy acetic acid (CPAs) herbicides. A polymeric monolith composed of methacrylic acid (MAA) and Zn/Cr-LDH was simply prepared in a polypropylene tube by in situ polymerization method. 2,4-Dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) were identified and measured using gas chromatography coupled to mass spectrometry (GC-MS). The fabricated composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FT-IR). The extraction efficiency was enhanced by optimizing crucial factors, such as salt concentration, sample solution pH, extraction, and desorption conditions. Under the optimum conditions, low detection limits (LODs) were obtained in the range of 0.01–0.05 ng mL−1 with good linearity in the range of 0.1–500 ng mL−1 and coefficient of determinations (R2) better than 0.9975. The inter and intra-assay precisions (RSD%, for n = 3) were achieved in the range of 7.1–8.2% and 6.8–7.9%, respectively. The monolithic composite displayed satisfying extraction performance and effective clean-up of CPAs from water samples.

Task specific microextraction column based on monolith for magnetic field-assisted in-tube solid phase microextraction of vanadium species in complex samples prior to online chromatographic analysis

The dominant species of vanadium (V) are V(IV) and V(V) which exhibit different toxicity and biological effects. Thus, speciation of V(IV) and V(V) is highly essential. Efficient sample preparation is the core step in the quantification of V(IV) and V(V). In the present study, a new task specific microextraction column based on monolith mingled with Fe3O4 nanoparticles (MBMC) was in situ synthesized in capillary and utilized as the extraction phase of magnetic field-assisted in-tube solid phase microextraction (MA-IT-SPME) of V(IV) and V(V) species which were coordinated with ethylene diamine tetraacetic acid (EDTA). The prepared MBMC presented porous and superparamagnetic properties, and possessed abundant functional groups. Results revealed that the exertion of magnetic field during adsorption and eluting steps boosted the extraction efficiency of V(IV)-EDTA and V(V)-EDTA chelates from 65.1 % to 55.7 %–90.0 % and 80.1 %, respectively. Under the beneficial extraction parameters, the established MA-IT-SPME was online hyphenated with HPLC/DAD to perform speciation of trace vanadium in water and vegetable samples, the achieved limits of detection were 0.054–0.060 μg/L and 1.4–1.5 μg/kg in water and vegetable samples, respectively, and the spiked recoveries varied from 82.5 to 118 %. In addition, relevant extraction mechanism under magnetic field was explored. In comparison with existing methods, the developed MA-IT-SPME technique displays some attractive merits such as automation, good anti-interference ability, high extraction efficiency, low cost and less use of organic solvent, in the capture of V species. The established online MBMC@MA-IT-SPME-HPLC/DAD system can become a competitive approach for sensitive speciation of V(IV) and V(V) at trace levels in complex samples.

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.

Electrodeposited histidine-(CuCr)layered double hydroxides/carbon dots for in-tube solid-phase microextraction of chlorophenols from water, juice, and honey samples followed by HPLC-UV

A novel adsorbent consisting of a composition of carbon dots and CuCr-layered double hydroxides intercalated with l-histidine (C-dots@His/LDHs) was introduced. This adsorbent was electrochemically deposited on the inner surface of a capillary copper tube. It was used as an adsorbent for in-tube solid-phase microextraction of chlorophenols (CPs). Separation and measurement of CPs were done by high-performance liquid chromatography-ultraviolet detector. The main parameters which had the most impact on the extraction efficiency and time such as extraction time and flow rate, desorption time and flow rate, ionic strength (salt concentration) and pH were optimized. Calibration curves (0.5–1000 μg L−1) were plotted in real sample (tap water) under optimal conditions which coefficients of determination better than 0.9893 and relative recoveries in the range of 88–120 % were obtained. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were obtained in the range of 0.1–1.0 μg L−1 and 0.3–3.0 μg L−1, respectively. The intra- and inter-assay precisions (RSD%, n = 3) were better than 5.9 and 8.8 %, respectively.

Simultaneous analysis of carcinogenic N-nitrosamine impurities in metformin tablets using on-line in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry

Contamination of active pharmaceutical ingredients (APIs) and pharmaceutical preparations with carcinogenic N-nitrosamines has led to recalls of these products and supply shortages to patients. The present study describes the development of a highly sensitive method for simultaneous analysis of seven N-nitrosamines using on-line in-tube solid-phase microextraction (IT-SPME) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine their actual contamination in metformin tablets. Using a Carboxen 1006 PLOT capillary as the extraction device for IT-SPME, these compounds were efficiently extracted and concentrated 6‒24-fold by subjecting 40 µL of sample to 25 repeated draw/eject cycles at a rate of 0.2 mL/min. The seven N-nitrosamines were separated within 11 min by gradient elution with 0.1 % formic acid solution and acetonitrile as the mobile phase using a CAPCELL PAK C18 MGII column and detected by multiple reaction monitoring in positive ion mode. The calibration curve showed linearity in the range 0.2‒50 ng/mL and detection limits (S/N = 3) in the range 3‒112 pg/mL. The intra-day and inter-day precisions were less than 5.5 % and 7.0 % (n = 6), respectively, with accuracies ranging from 93‒117 %. Following ultrasonic extraction with water, centrifugation and filtration of the supernatant liquid through a membrane filter, the N-nitrosamine impurities in metformin tablets could be analyzed by IT-SPME/LC‒MS/MS. Their limits of quantification (S/N = 10) were 0.1‒5.1 pg/mg API and recoveries ranged from 87‒102 %. Analysis of eight metformin tablets from eight manufacturers showed that 5.8‒7.5 pg/mg N-nitrosodimethylamine were present in three tablets, with no other N-nitrosamines detected in any of the eight tablets. This method may be useful in testing for N-nitrosamine impurities in pharmaceutical preparations.

Packed in-tube solid-phase microextraction with mesoporous zirconium titanium oxides for highly efficient phosphopeptide enrichment and analysis

Phosphorylated peptides are crucial for understanding biological regulation processes. However, the detection of phosphorylated peptides remains challenging in mass spectrometry (MS) due to their high hydration, low abundance, and the significant signal suppression caused by non-phosphorylated peptides. It is essential to enhance the efficiency of phosphopeptide enrichment from complex biological samples to achieve comprehensive analysis and identification of phosphopeptides. Herein, a packed in-tube solid-phase microextraction (IT-SPME) method was developed based on mesoporous zirconium titanium oxides for the selective enrichment and analysis of phosphopeptides. The IT-SPME system achieved the efficient capture of phosphopeptides from complex biological samples followed by high-sensitivity detection (5 fmol). This exceptional performance can be attributed to the high surface area (289.77 m2/g) of mesoporous zirconium titanium oxides, which provided abundant active sites for a high loading capacity. The zirconium titanium oxides with a mesoporous structure (∼4.5 nm) was prepared through a sol–gel and solvothermal process. Importantly, this method proved effective in enriching phosphopeptides from practical samples such as non-fat milk and egg white. It is the first attempt to employ a mesoporous packed IT-SPME approach for phosphopeptide enrichment. These results demonstrate the significant application potential of mesoporous zirconium titanium oxides in phosphoproteomics.

Biochar nanosphere-functionalized carbon fibers for in-tube solid-phase microextraction of polycyclic aromatic hydrocarbons in environmental water followed by liquid chromatography and diode array detection.

In order to improve the extraction ability of carbon fibers (CFs) for microextraction ofpolycyclic aromatic hydrocarbons (PAHs), biochar nanospheres derived from glucose were in-situ grown onto the surface of CFs via hydrothermal synthesis. The surface morphology and elemental composition of biochar nanospheres-CFs were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. Thereafter, the biochar nanosphere-CFs were pulled into the polyetheretherketone tube for solid-phase microextraction, and the tube was combined with high-performance liquid chromatography-diode array detector to online detect PAHs. With the help of π-stacking, hydrophobic, and hydrophilic effect of biochar nanospheres, the extraction efficiency of CFs was greatly enhanced (enrichment factor increased by 293% compared with the original). The conditions affecting the analytical performance (sampling volume, sampling rate, methanol content, and desorption time) were investigated. Under the optimal conditions, an online analytical method for microextraction and determination ofseveral PAHs was developed, and satisfactory results were achieved. The limits of detection were 0.003-0.010 ng mL-1 owing to high enrichment effect (2973-3600), linearity ranged from 0.010-15.0 ng mL-1, andrelative standard deviations were 0.4%-1.6% (intra-day) and 2.4%-4.4% (inter-day), respectively. The method was applied toanalyze environmental water samples (rain water, snow water, and river water), and spiked recoveries within 80.0%-119% were obtained.

Determination of chlorophylls a and b and β-carotene in environmental waters: Diminishing wastes and analysis time by in-tube solid-phase microextraction coupled on-line to nano liquid chromatography

Chlorophylls and carotenoids are indicators of water quality. A new method based on in-tube solid-phase microextraction (IT-SPME) coupled on-line to nano-liquid chromatography with diode array detection (NanoLC-DAD) was developed. This paper aims to provide selectivity and sensitivity with a short analysis time of about 10 min and low residues of friendly solvents, 5 µL/run of ethanol:water 95:5 and 250 µL of ethanol for dissolving the pigments retained in a nylon filter (0.45 µm, 13 mm) from 30 mL of water. IT-SPME capillary was a fused silica capillary (10 cm length x 75 µm internal diameter, i.d.) with a coating of tetraethyl orthosilicato (TEOS), triethoximethylsilane (MTEOS) doped with SiO2 nanoparticles (NPs) and an analytical column Zorbax 300SB-C18 (50 mm x 75 µm i.d., 3.5 µm particle size) was used. The recovery obtained to chlorophyll a, chlorophyll b and β-carotene were 93 ± 8 %, 92 ± 7 % and 94 ± 4 %, respectively. The method shows good linearity in the range up to 300 µg L−1 for chlorophyll a and β-carotene and up to 600 µg L−1 for chlorophyll b. The achieved limits of detection (LODs) in samples were 0.1 µg L−1 to chlorophyll a and β-carotene, and 0.2 µg L−1 to chlorophyll b. Values of relative standard deviations (RSD) expressed in% between 2 and 3 were obtained. Pigments were successfully determined with a short analysis time and minimal residues in real water samples.

In-situ preparation of β-cyclodextrin-crosslinked polymer coated glass fiber for in-tube solid-phase microextraction of polycyclic aromatic hydrocarbons from water samples

Governments and organizations are paying increasing attention to the monitoring of polycyclic aromatic hydrocarbons (PAHs) in the environment. In this study, a β-cyclodextrin-based hyper-crosslinked polymer (β-CD-HCP) was prepared via the Friedel–Crafts reaction and used as a coating for an in-tube solid-phase microextraction (IT-SPME) glass fiber based on an in-situ preparation method. Subsequently, it was used for the analysis of six PAHs in water samples. The β-CD-HCP showed an excellent adsorption performance for the PAHs owing to its unique structural characteristics and multiple bonding forces (hydrophobic interaction, π–π, and electrostatic interactions) between the β-CD-HCP and PAHs. The adsorption mechanism of the β-CD to PAHs was investigated using density functional theory calculation experiments. By coupling high-performance liquid chromatography with a diode array detector, an online analysis method was established for the PAHs with a wide linear range (0.01–20 µg L–1), high enrichment factor (2130–2670), and low limits of detection (0.004–0.008 µg L–1). The PAHs in the water samples were successfully analyzed using this proposed online method with satisfactory recoveries in the range of 79.9–106.7% and relative standard deviations under 4.0%. The above results demonstrate that the prepared β-CD-HCP-based IT-SPME glass fiber has good application prospects for the pretreatment of PAHs in various aqueous environmental samples.

Monolithic column with multiple COF surface layers via an in-situ surface self-assembly strategy for efficient in-tube solid-phase microextraction of benzodiazepines

Covalent organic framework (COF)-based monolithic columns have been extensively used for sample preparation. In order to maximize the COF extraction properties, it is attractive to increase the COF surface coverage of the COF-based monolithic column. Herein, a novel monolithic column with multiple COF surface layers was prepared via an in-situ surface self-assembly strategy to increase the COF surface coverage. For this preparation, the poly (p-phenylenediamine) (PPDA) fibers were first grafted onto the parent monolith. Then, due to the abundant NH2-anchor sites of the PPDA fiber, a large number of COF microspheres were self-assembled on PPDA fibers, and further interlinked with each other to form multiple COF surface layers on the monolith, which further improve the COF surface coverage. Various characterization techniques were employed to confirm this successful preparation. Benefiting from the enhanced COF surface coverage, the developed monolith exhibited superior extraction ability towards benzodiazepines (BZDs), which are central nervous system depressants that are tightly controlled by governments. The hydrophobic and π-π stacking interactions should be the main adsorption mechanism for in-tube SPME of BZDs. Under the optimal SPME conditions, a simple in-tube SPME-HPLC-DAD method was established for the detection of trace BZDs in saliva, with a wide linear range (5 ∼ 300 ng/mL), excellent sensitivity (LODs ≤ 2 ng/mL) and satisfactory recoveries (81.4% ∼ 98.0%). This research provided a versatile route to fabricate the COF-based monolith with high surface coverage, demonstrating its great potential in efficient sample preparation.

Adoption of new strategy for molecularly imprinted polymer based in-tube solid phase microextraction to improve specific recognition performance and extraction efficiency

In-tube solid phase microextraction (IT-SPME) utilizing molecularly imprinted polymers (MIPs) as extraction phase has received wide attention due to various merits. However, low extraction efficiency and unsatisfactory recognition performance have limited its extensive application. To circumvent the limitations, a new strategy that implementation of magnetic fields during extraction stage was introduced to improve the extraction efficiency and recognition performance of MIPs-based IT-SPME. Firstly, using 2,4-dinitroaniline (2,4-DNA) as model template, a MIP mingled with magnetic nanoparticles (Fe3O4) was in-situ prepared in a capillary and employed as the microextraction column of IT-SPME. In the second step, a magnetic coil was wrapped the as-prepared MIP-based microextraction column so as to produce variable magnetic fields in extraction step. Results revealed that the application of magnetic field during the adsorption step improved the specific extraction performance towards template. The extraction efficiency and imprinting factor towards 2,4-DNA increased from 58% and 2.5 to 81% and 3.1, respectively. Practicality of the introduced magnetism-assisted IT-SPME technique based on MIP was demonstrated by on-line hyphenating with HPLC/DAD to quantify trace 2,4-DNA in a variety of environmental waters. High sensitivity (limit of detection was 0.060 μg/L), good precision (RSDs were below 10%) and satisfactory recoveries (82.1–111%) were obtained. Furthermore, the possible selective extraction mechanism under magnetic fields was deduced.

MXene nanosheets woven in polyacrylonitrile nanofiber yarns aligned spider web as a highly efficient sorbent for in-tube solid phase microextraction of beta-blockers from biofluids

The use of electrospinning has received much attention in the production of nanofiber webs due to its advantages such as flexibility and simplicity. The direct electrospinning of nanofibers in an aligned or twisted form and the production of nanofiber yarns can turn nanofibers into woven fabrics, which leads to an increase in the diversity of nanofiber applications and improves their end-use possibilities. In this work, a victorious nanofiber yarn spinning system was used with the help of a rotating funnel. Yarn formation was studied using a composited polyacrylonitrile (PAN)/MXene polymer solution ejected from two oppositely charged nozzles. Finaly their application for packed-in-tube solid-phase microextraction of β-blocker drugs from biofluids was demonstrated. The separation and quantification of analytes were performed by HPLC-UV instrument. The 3D-yarn PAN/MXene sorbent exhibited high flexibility, porosity, sorbent loading, mechanical stability, and a long lifetime. The characterization of the final nanofiber was carried out utilizing Fourier-transform infrared spectroscopy, field emission scanning electron microscope, energy-dispersive X-ray mapping, transmission electron microscope and X-ray diffraction analysis. Various parameters that affect the extraction efficiency, such as extraction time, pH, ionic strength and flow rate of sample solution, and type, volume and flow rate of eluent, were investigated and optimized. Under optimized conditions, the limits of detection were obtained in the range of 1.5–3.0 μg L−1. This method demonstrated appropriate linearity for β-blockers in the range of 5.0–1000.0 μg L−1, with coefficients of determination greater than 0.990. The inter- and intra-assay precisions (RSDs, for n = 3) are in the range of 2.5–3.5%, and 4.5–5.2%, respectively. Finally, the validated method was put in an application for the analysis of atenolol, propranolol and betaxolol in human urine and saliva samples at different hours and acceptable relative recoveries were obtained in the range of 89.5% to 110.4%.

Determination of antioxidant activity by in situ synthesis of AgNPs using in-tube SPME coupled on-line to capillary liquid chromatography

A chromatographic system based on in-tube SPME coupled to capillary LC-DAD has been used to study the synthesis of silver nanoparticles using polyphenols in different scenarios: excess of the reducing agent or of the silver salt, addition of the cationic surfactants, and thermal synthesis. The optimized synthesis conditions allowed to quantify the polyphenols used as reducing agents, such as Trolox and chlorogenic acid. Two chromatographic peaks with different absorption spectrum were monitored during the syntheses. Depending on the molar relationship, a linear relation between the area of the chromatographic peaks and the concentration of the silver or polyphenol was established. For stabilization of silver nanoparticles, different cationic surfactants were used allowing to evaluate the role of anion (chloride and bromide) and of the alkyl chain. The proposed methodology can be used to determine chlorogenic acid up to 3 mM with a detection limit of 34 μM at λ= 400 nm. Chlorogenic acid was determined in dietary products with successful results. Precision (RSD=10%) and recovery (97–100%) were also satisfactory.Graphical

Recent Trends in Graphene-Based Sorbents for LC Analysis of Food and Environmental Water Samples.

This review provides an overview of recent advancements in applying graphene-based materials as sorbents for liquid chromatography (LC) analysis. Graphene-based materials are promising for analytical chemistry, including applications as sorbents in liquid chromatography. These sorbents can be functionalized to produce unique extraction or stationary phases. Additionally, graphene-based sorbents can be supported in various materials and have consequently been applied to produce various devices for sample preparation. Graphene-based sorbents are employed in diverse applications, including food and environmental LC analysis. This review summarizes the application of graphene-based materials in food and environmental water analysis in the last five years (2019 to 2023). Offline and online sample preparation methods, such as dispersive solid phase microextraction, stir bar sorptive extraction, pipette tip solid phase extraction, in-tube solid-phase microextraction, and others, are reviewed. The review also summarizes the application of the columns produced with graphene-based materials in separating food and water components and contaminants. Graphene-based materials have been reported as stationary phases for LC columns. Graphene-based stationary phases have been reported in packed, monolithic, and open tubular columns and have been used in LC and capillary electrochromatography modes.