A high-throughput nanofibers mat-based micro-solid phase extraction for the determination of cationic dyes in wastewater

Development of a mesoporous polypyrrole nanofiber mat for simultaneous detection of multiple mycotoxins in various foods

Due to health hazards and co-contamination of mycotoxins, efficient separation and detection of multiple mycotoxins in food is highly desirable yet challenging. In this study, we prepared a novel mesoporous polypyrrole nanofiber mat (M-PPy NFM) for extracting multiple mycotoxins from food. The mesoporous effects and multifunctional PPy contribute to higher recovery and purification efficiency of M-PPy NFM for mycotoxins by facilitating hydrogen bonding and π-π interaction. Under optimized conditions, a simple, eco-friendly solid phase extraction (SPE) method coupled with high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) was developed for mycotoxin detection. This innovative method demonstrates good linearity (0.9991-0.9999), low detection limits (0.03-0.33 μg kg-1), satisfactory recoveries (92.0 %-108.0 %) and precision (0.3 %-11.7 %). Notably, it significantly reduces organic solvent consumption to 3.1 mL while minimizing adsorbent usage to 5.0 mg. Moreover, M-PPy NFM could be reused ten times. This study confirms the huge potential of M-PPy NFM for efficient applications in mycotoxin extraction and determination.

Simple and rapid determination of tartrazine in fake saffron using the metal organic framework (Fe SA MOF@CNF) by HPLC/PDA

The present study of a novel metal-organic framework containing Fe single atoms doped on electrospun carbon nanofibers (Fe SA-MOF@CNF) based on dispersive micro solid phase extraction (D-μ-SPE) using HPLC-PDA for detection tartrazine in fake saffron samples was designed. The Fe SA-MOF@CNF sorbent was extensively characterized through various techniques including N2 adsorption-desorption isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The specific area of surface of the sorbent was 577.384 m2/g. The study variables were optimized via the central composite design (CCD), which included a sorbent mass of 15 mg, a contact time of 6 min, a pH of 7.56, and a tartrazine concentration of 300 ng/ml. Under the optimum condition, the calibration curve of this method was linear in the range of 5-1000 ng/mL, with a correlation coefficient of 0.992. The LOD and LOQ values were ranged 0.38-0.74 and 1.34-2.42 ng/ml, respectively. This approach revealed significant improvements, including high extraction recovery (98.64), recovery rates (98.43-102.72%), and accuracy (RSDs < 0.75 to 3.6%). the enrichment factors were obtained in the range of 80.6-86.4 with preconcentration factor of 22.3. Consequently, the D-μ-SPE method based on synthesized Fe SA-MOF@CNF could be recommended as a sustainable sorbent for detecting tartrazine in saffron samples.

Determination of restricted dyes in textile raw material solid wastes by ultra-high performance liquid chromatography-tandem mass spectrometry

A rapid and highly sensitive method for the quantification of 34 restricted dyes (including acid, basic, disperse, direct, and azo dyes) in solid textile raw material wastes was developed by employing ultrasonic extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry(UHPLC-MS/MS). More specifically, the proposed method employed methanol as the extraction solvent, while the mobile phases consisted of acetonitrile and 10 mmol/L ammonium acetate + 0.05% ammonia. A good linearity was achieved over the concentration range of 0.01-200 ng/mL with correlation coefficients (R) between 0.991-0.999, limits of detection (LODs) of 0.25-40.0 µg/kg (S/N = 3) and limits of quantification (LOQs) of 0.84-133.4 µg/kg (S/N = 10). 34 dyes were recovered at three levels ranging from 84.5 to 106.9% with relative standard deviation (RSDs) ranging from 0.59% to 10.61%. Further, the method was applied for the accurate analysis of 32 counts of cotton yarn, waste cotton, and printed fabrics within 15 min. The dyestuffs accurately quantified by this rapid chromatographic procedure covered a wide range of carcinogenic and allergenic dyestuffs listed in the Oeko-Tex Standard 100 (version 02.2023) colourants. The ultrasound technique combined with the ultra-high performance liquid chromatography-tandem mass spectrometry method proposed in this work is thus suitable for the rapid screening, confirmation, and quantitative detection of industrial synthetic dyes within solid waste originating from textile raw materials.

Electrophoretically deposited sulfonated poly(styrene-co-divinylbenzene) on a screw for microextraction of cationic dyes from aqueous solutions

In the present work, a novel solid-phase microextraction on a screw (MES) was employed to extract cationic dyes (malachite green, methylene blue, and rhodamine B) from food samples and fish breeding pool water. The sulfonated poly(styrene-co-divinylbenzene) was electrophoretically deposited on the surface of the grooves of a screw. Then the screw was placed inside a silicon tube as a holder to create a channel to run a test solution through it. The extracted dyes on the coated screw were eluted by a suitable eluent. High-performance liquid chromatography with an ultraviolet/visible detector was utilized for the separation and analysis of the analytes. The effective parameters of the analyte extraction efficiency were optimized. Under optimum conditions, the limits of detection were 0.15 μg/L, and calibration curves were linear in the range of 0.50-250.00 μg/L, with coefficients of determination > 0.989 for all studied dyes. The relative standard deviations of intra and inter-day (n = 3) were in the range of 2.8%-7.0% and 7.0%-9.5%, respectively. The MES was applied as a simple and repeatable method with acceptable relative recoveries (82.0%-103.0%) for the determination of cationic dyes in grape nectar, ice pop, jelly powder, and fish breeding pool water.

Efficient adsorptive removal of aminoglycoside antibiotics from environmental water

Aminoglycoside antibiotics (AGs) in environmental water are emerging pollutants that must be removed to protect human health and the ecosystem. However, removing AGs from environmental water remains a technical challenge due to high polarity, stronger hydrophilicity and unique characteristics of polycation. Herein, a thermal-crosslinked polyvinyl alcohol electrospun nanofiber membrane (T-PVA NFsM) is synthesized and firstly leveraged as the adsorptive removal of AGs from environmental water. The thermal crosslinking strategy is demonstrated to enhance both the water resistance and hydrophilicity of T-PVA NFsM, thereby effectively interacting with AGs with high stability. Experimental characterizations and analog calculations indicate that T-PVA NFsM utilizes multiple adsorption mechanisms, including electrostatic and hydrogen bonding interactions with AGs. As a result, the material achieves 91.09%-100% adsorption efficiencies and a maximum adsorption capacity of 110.35 mg g^-1 in less than 30 min. Furthermore, the adsorption kinetics follow the pseudo-second-order model. After eight consecutive adsorption-desorption cycles, T-PVA NFsM with a simplified recycling process maintains a sustainable adsorption capability. Compared with other forms of adsorption materials, T-PVA NFsM has significant advantages such as less consumption of adsorbent, high adsorption efficiency and fast removal speed. Therefore, T-PVA NFsM-based adsorptive removal holds promise for eliminating AGs from environmental water.

Post-synthetic modification of a magnetic covalent organic framework with alkyne linkages for efficient magnetic solid-phase extraction and determination of trace basic orange II in food samples

Efficient magnetic solid phase extraction using covalent organic frameworks (COFs) can find important applications in food safety. In this work, a sulfonate-functionalized magnetic COF (Fe₃O₄@COF-SO₃Na) was synthesized by self-polycondensation of two-in-one monomer 1,6-bis(4-formylphenyl)-3,8-bis((4-aminophenyl) ethynyl)) pyrene (BFBAEPy) on the surface of aminated Fe₃O₄ and a thiol-yne click reaction. It was further adopted as an adsorbent for the efficient magnetic solid-phase extraction (MSPE) of basic orange II. The selective adsorption experiment indicated that it displayed selective adsorption ability to basic orange II due to the ion exchange, hydrogen bonds, and π-π interactions. Under the optimized conditions, the proposed MSPE method coupled with HPLC-DAD showed excellent linearity in the range of 0.05-0.5 µg/mL (R² = 0.9997) for basic orange II. The lower limits of detection (LODs) for basic orange II were 1.0-1.4 µg/L for three food samples: yellow croaker, paprika and dried bean curd. The recoveries were 90.1-98.8% with relative standard deviations (RSDs) below 4.2%. Therefore, this work provides an effective strategy to modify magnetic COFs as absorbents in MSPE. Due to the tunability of functional groups in thiol‑yne click reactions, the functional groups of magnetic COFs can be readily designed to enrich their multifunctional applications. Meanwhile, this work proposed a new method to detect trace amounts of basic orange II in food samples.

Solid Phase Extraction for the Determination of Methylene Blue Using Lignocellulosic Biosorbent in Aqueous Solutions

The recent introduction of a large number of synthetic dyes, which are toxic, mutagenic, and carcinogenic, has made the situation worse by disrupting normal aquatic life. For this reason, the detection and removal of dyestuffs in wastewater become important. In this study, for the extraction of methylene blue, used as solid phase extraction adsorbent, lignocellulosic biosorbent of tea waste activated with ZnCl₂ was prepared. The factors affecting its extraction were studied in detail. To determine the sensitivity and certainty of the solid phase extraction process; optimized to have an adsorbent amount (75 mg), wash solvent (3 mL water), loading volume (20 mL), elution solvent methanol/acetic acid (80:20, v/v), and eluent volume (8 mL). As a result of the optimization processes, rates ranging from 94.4% to 98.9% recovery were obtained in methylene blue extraction in aqueous solutions. According to the results obtained, this method can be extensively applied in the efficient removal of colored contaminants.

Simultaneous Determination of Nine Quinolones in Pure Milk Using PFSPE-HPLC-MS/MS with PS-PAN Nanofibers as a Sorbent

In this study, a packed-fiber solid-phase extraction (PFSPE)-based method was developed to simultaneously detect nine quinolones, including enrofloxacin (ENR), ciprofloxacin (CIP), ofloxacin (OFL), pefloxacin (PEF), lomefloxacin (LOM), norfloxacin (NOR), sarafloxacin (SAR), danofloxacin (DAN), and difloxacin (DIF), in pure milk, using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). Polystyrene (PS) and polyacrylonitrile (PAN) were combined to form PS-PAN composite nanofibers through electrospinning. The nanofibers were used to prepare the home-made extraction columns, and the process was optimized and validated using blank pure milk. The analytical method showed high accuracy, and the recoveries were 88.68–97.63%. Intra-day and inter-day relative standard deviations were in the ranges of 1.11–6.77% and 2.26–7.17%, respectively. In addition, the developed method showed good linearity (R² ≥ 0.995) and low method quantification limits for the nine quinolones (between 1.0–100 ng/mL) for all samples studied. The nine quinolones in the complex matrix were directly extracted using 4.0 mg of PS-PAN composite nanofibers as a sorbent and completely eluted in 100 μL elution solvent. Therefore, the developed PFSPE-HPLC-MS/MS is a sensitive and cost-effective technique that can effectively detect and control nine quinolones in dairy products.

Urea-linked covalent organic framework functionalized polytetrafluoroethylene film for selective and rapid thin film microextraction of rhodamine B

Incorporation of highly selective and stable adsorbent with facile extraction technology is desired in practical analysis. Here we show the rational preparation of a urea-linked covalent organic framework functionalized polytetrafluoroethylene film (COF-117-PTFE) with ordered porous structure, rich functional groups, and large surface area-to-volume ratio as the effective adsorbent for convenient, selective and rapid thin film microextraction (TFME) of rhodamine B (RB). The COF-117-PTFE based TFME coupled with high performance liquid chromatography-fluorescence detector (HPLC-FLD) successfully realized the determination of RB with the limit of detection of 0.007 μg L^-1, the linear range of 0.1 - 100 μg L^-1. The relative standard deviation (RSD) of intraday (n = 5) and interday (n = 5) for the determination of 10 μg L^-1 RB were 2.3% and 6.8%, respectively. The absolute recoveries were 80.3%, 71.2% and 67.9% in river water, chili powder and Sichuan pepper powder, respectively. The recoveries for RB spiking in complicated real samples (dry chili, chili powder, dry Sichuan pepper, Sichuan pepper powder and river water) ranged from 90.4% to 107.5%. The developed COF-117-PTFE based TFME-HPLC-FLD method is promising in practical application. This work reveals the high potential of functionalized COF film as the adsorbent for effective extraction of trace contaminants in complicated samples.

Rapid Purification of Fucoxanthin from Phaeodactylum tricornutum

Fucoxanthin is a natural marine xanthophyll and exhibits a broad range of biological activities. In the present study, a simple and efficient two-step method was used to purify fucoxanthin from the diatom, Phaeodactylum tricornutum. The crude pigment extract of fucoxanthin was separated by silica gel column chromatography (SGCC). Then, the fucoxanthin-rich fraction was purified using a hydrophile-lipophile balance (HLB) solid-phase extraction column. The identification and quantification of fucoxanthin were determined by high-performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS). This two-step method can obtain 92.03% pure fucoxanthin and a 76.67% recovery rate. In addition, ¹H and ¹³C NMR spectrums were adopted to confirm the identity of fucoxanthin. Finally, the purified fucoxanthin exhibited strong antioxidant properties in vitro with the effective concentration for 50% of maximal scavenging (EC50) of 1,1-Dihpenyl-2-picrylhydrazyl (DPPH) and 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radicals being 0.14 mg·mL^-1 and 0.05 mg·mL^-1, respectively.

Removal of Ionic Dyes by Nanofiber Membrane Functionalized with Chitosan and Egg White Proteins: Membrane Preparation and Adsorption Efficiency

Electrospun polyacrylonitrile (PAN) nanofiber membrane was functionalized with chitosan and proteins for use in the treatment of dye-containing wastewater. The PAN nanofiber membrane was subjected to alkaline hydrolysis, before being grafted with chitosan and subsequently the proteins from chicken egg white. The resultant nanofiber membrane (P-COOH-CS-CEW) was comprehensively characterized using thermogravimetric analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy. The efficiency of P-COOH-CS-CEW in removing cationic dye toluidine blue O (TBO) and anionic dye acid orange 7 (AO7) in aqueous solution was evaluated. Based on the performance of model fitting, Langmuir and pseudo-second-order kinetic model could be used to describe the performance of P-COOH-CS-CEW in the removal of TBO (pH 10) and AO7 (pH 2) from the dye solutions. The adsorbed TBO and AO7 dyes can be completely desorbed by an elution solution made of 50% (v/v) ethanol and 1 M sodium chloride. After five consecutive adsorption-desorption cycles, the efficiency of dye removal by P-COOH-CS-CEW was maintained above 97%.

Magnetic Solid-Phase Extraction Based on Magnetic Sulfonated Reduced Graphene Oxide for HPLC-MS/MS Analysis of Illegal Basic Dyes in Foods

In this study, a magnetic solid-phase extraction (MSPE) method coupled with High-Performance Liquid Chromatography Mass Spectrometry (HPLC–MS/MS) for the determination of illegal basic dyes in food samples was developed and validated. This method was based on Magnetic sulfonated reduced graphene oxide (M-S-RGO), which was sensitive and selective to analytes with structure of multiaromatic rings and negatively charged ions. Several factors affecting MSPE efficiency such as pH and adsorption time were optimized. Under the optimum conditions, the calibration curves exhibited good linearity, ranging from 5 to 60 µg/g with correlation coefficients >0.9950. The limits of detection of 16 basic dyes were in the range of 0.01–0.2 µg/L. The recoveries ranged from 70% to 110% with RSD% < 10%. The results indicate that M-S-RGO is an efficient and selective adsorbent for the extraction and cleanup of basic dyes. Due to the MSPE procedures, matrix effect and interference were eliminated in the analysis of HPLC–MS/MS without the matrix-matched standards. Thus, validation data showed that the proposed MSPE–HPLC–MS/MS method was rapid, efficient, selective, and sensitive for the determination of illegal basic dyes in foods.

Solvent-free mechanochemical preparation of graphene oxide-Fe3 O4 and its application in magnetic dispersive solid-phase extraction of illegal dyes in food samples

A simple, green, and efficient mechanochemical approach was developed herein to prepare tunable magnetic graphene oxide nanoparticles. The obtained nanoparticles were successfully used as adsorbents in a magnetic dispersive solid-phase extraction method to extract three cationic dyes (i.e., thioflavine T, auramine-O, and basic orange 2) found in food samples. Our proposed approach also utilized high-performance liquid chromatography with ultraviolet detection. Several key variables affecting the extraction recovery were investigated. These included the sample pH, amount of extractant, extraction time, sample volume, elution solvent type and volume, and the stability and reusability of the magnetic graphene oxide nanoparticles. Under optimized conditions, the calibration curve was linear at a concentration range of 0.005-1.0 μg/mL with a correlation coefficient of 0.9992-0.9996. Moreover, the limits of detection were determined at 0.97-1.35 μg/mL. The extraction mechanism was investigated via ultraviolet-visible spectrophotometry and zeta-potential analyses. The developed method was used to analyze the above-mentioned cationic dyes in bean products and yellow fish samples. Notably, satisfactory spiked recoveries ranging from 90.7 to 104.9% were achieved.

Synchronous Construction of Hierarchical Porosity and Thiol Functionalization in COFs for Selective Extraction of Cationic Dyes in Water Samples

Pore size and functionalization are two critical factors for covalent organic frameworks (COFs) as effective adsorbents. However, due to the low crystallinity of COFs, it is a grand challenge to accomplish pore diameter adjustment and functionalization at the same time. In this work, we developed a simple and ingenious strategy, cutting off linkage, to synchronously construct hierarchical porosity and modify thiol groups in COFs under mild conditions. The hybrid COFs containing disulfide bonds were designed and synthesized, and then the disulfide bonds were cleaved by glutathione, resulting in the formation of thiol groups as well as the increase in pore size caused by skeleton defects. The pore diameter of thiol-functionalized hierarchical porous COFs (denoted as HP-TpEDA-SH) was concentrated at 2.6 and 3.5 nm. Thanks to the electrostatic attraction of thiol groups to cationic dyes and the higher number of available adsorption sites, the maximum extraction amounts of methylene blue (MB), malachite green (MG), and crystal violet (CV) by HP-TpEDA-SH were 2.6, 2.1, and 3.3 times those of microporous COFs under optimal extraction conditions, respectively. The proposed analytical method (solid-phase extraction-high-performance liquid chromatography/ultraviolet (SPE-HPLC/UV)) with HP-TpEDA-SH as the adsorbent showed low detection limits of 1.3, 0.13, and 0.12 μg·L^-1 for MB, MG, and CV, respectively. The recoveries of three spiked water samples ranged from 81.5 to 113.8%, with relative standard deviations (RSDs) less than 9.7%. This work not only opened a new avenue for the preparation of functionalized hierarchical porous COFs but also established an effective method for detecting trace cationic dyes in fishery water.

Rapid determination of seven synthetic dyes in casual snacks based on packed-fibers solid-phase extraction coupled with HPLC-DAD

Based on packed-fiber solid-phase extraction and HPLC-DAD, a simple analytical method for the determination of seven synthetic dyes has been successfully developed. Polystyrene/polypyrrole (PS/PPy) fibers were obtained via electro-spinning of polystyrene skeletal nanofibers, followed by the oxidation with FeCl₃ to trigger the polymerization of pyrrole and the deposition of polypyrrole coatings on PS fibrous skeleton fibers. The relationship between the extraction performance of the fibers and the electrospinning process at different humidities was investigated based on morphologic study and BET surface area. In the extraction process, purification, concentration, and desorption could be accomplished in one step. The established method exhibited good sensitivity, selectivity, reproducibility, and good efficiency for synthetic dyes in casual snacks (preserved fruit, flavored yogurt, and fruity hard candy) samples. With optimal conditions, the LODs (S/N = 3) were 2.4 to 21.09 ng mL^-1, and linearities were acceptable in liquid matrix and solid matrices. The recoveries were 93.9-103.9%.

Removal of dye waste by weak cation-exchange nanofiber membrane immobilized with waste egg white proteins

In this research, a protein nanofiber membrane (P-COOH-CEW) was developed to treat the dye waste. Initially, polyacrylonitrile nanofiber membrane (PAN) was prepared by electrospinning, followed by heat treatment, alkaline treatment, and neutralization to obtain weak cation exchange nanofiber membrane (P-COOH). The P-COOH membrane was chemically coated with chicken egg white (CEW) proteins to obtain a 3D structure of complex protein nanofiber membrane (P-COOH-CEW). The composite prepared was characterized with Fourier Transform Infrared analysis (FTIR), Scanning Electron Microscopy (SEM), and thermogravimetric analysis (TGA). Further, the composite was evaluated by investigating the removal of Toluidine Blue O (TBO) from aqueous solutions in batch conditions. Different operating parameters - coupling of CEW, shaking rate, initial pH, contact time, temperature, and dye concentration were studied. From the results, maximum removal capacity and equilibrium association constant was determined to be 546.24 mg/g and 10.18 mg/mg, respectively at pH 10 and 298 K. The experimental data were well fitted to pseudo-second order model. Furthermore, desorption studies revealed that the adsorbed TBO can be completely eluted by using 50% ethanol or 50% glycerol in 1 M NaCl solution. Additionally, the reuse of P-COOH-CEW membrane reported to have 97.32% of removal efficiency after five consecutive adsorption/desorption cycles.

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

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

Sodium 4-styrenesulfonate functionalized nanofibers mat as 96-well plate solid-phase extraction adsorbent for quantitative determination of multiple β-agonists residues in pork samples

In this work, sodium 4-styrenesulfonate functionalized polyacrylonitrile nanofibers mat (SS/PAN NFM) was firstly prepared and applied as 96-well plate solid-phase extraction adsorbent for quantitative determination of seven β-agonists residues in pork samples. The functional modification endowed the SS/PAN NFM with superior adsorption performance for target β-agonists. The adsorption process is spontaneous (ΔG < 0), the initial adsorption rate can reach 6.03-9.09 mg/g/min and the maximum adsorption capacity is calculated to be 48.3 mg/g at 298 K. Moreover, SS/PAN NFM can be reused for 12 times without degradation in adsorption capability. Combined with UPLC-MS/MS, the limits of detection can reach 0.006-0.24 μg/kg, the recoveries ranged from 87.2% to 111% and the relative standard deviations of intra-day and inter-day precisions were in the scope of 1.75%-11.6% and 5.08%-13.5%, respectively. The obtained results fully demonstrated the practicability of this method in preventing the hazard of β-agonists residues.

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

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

Coupling of micro-solid-phase extraction and internal extractive electrospray ionization mass spectrometry for ultra-sensitive detection of 1-hydroxypyrene and papaverine in human urine samples

Quantification of ultra-trace analytes in complex biological samples using micro-solid-phase extraction followed by direct detection with internal extractive electrospray ionization mass spectrometry (μSPE-iEESI-MS) was demonstrated. 1-Hydroxypyrene (1-OHP) and papaverine at attomole levels in human raw urine samples were analyzed under negative and positive ion detection mode, respectively. The μSPE was simply prepared by packing a disposable syringe filter with octadecyl carbon chain (C18)-bonded micro silica particles, which were then treated as the "bulk sample" after the analytes were efficiently enriched by the C18 particles. Under the optimized experimental conditions, the analytes were readily eluted by isopropanol/water (80/20, V/V) at a high voltage of ± 4.0 kV, producing analyte ions under ambient conditions. The limit of detection (LOD) was 0.02 pg/L (9.2 amol) for 1-hydroxypyrene and 0.02 pg/L (5.9 amol) for papaverine. The acceptable linearity (R² > 0.99), signal stability (RSD ≤ 10.7%), spike recoveries (91-95%), and comparable results for real urine samples were also achieved, opening up possibilities for quantitative analysis of trace compounds (at attomole levels) in complex bio-samples. Graphical abstract.

A Rapid Enrichment Technique for the Ultratrace Determination of Nickel in Water Samples Using a Nanofiber-composite Membrane Filter

A new method for the rapid enrichment and highly sensitive determination of nickel ion has been developed by using a nanofiber-composite membrane filter, which was fabricated by stacking a nanofibrous material made of nylon 6 over a water-permeable membrane filter. The noncharged nickel-α-furil dioxime complex was adsorbed on a nanofibrous layer of the membrane filter under significantly higher flow rates than those used for conventional solid-phase extraction techniques. Highly sensitive determinations with detection limits at sub-parts per billion levels were achieved by enrichment from 50 mL of the complex solution, and the enrichment was completed within 3 min. The color that was developed on the membrane filter was successfully subjected to visual colorimetric analysis and quantitative determination by solid-phase spectrophotometry. In addition, colorimetric determination was feasible with a handheld spectrometer after elution of the colored agent with 50 μL of acetone. This combination of rapid enrichment and spectrometric measurement in a small-volume sample provides a useful analytical method suitable for on-site analysis, which requires neither expensive instruments nor high laboratory skills.

Aminated Polyethylene Terephthalate (PET) Nanofibers for the Selective Removal of Pb(II) from Polluted Water

Electrospun nanofibers have been successfully applied to remove toxic and carcinogenic contaminants such as heavy metals from polluted water. In this study, an efficient adsorbent based on poly(ethylene terephthalate) (PET) nanofibers was developed following a cheap, versatile and scalable process. PET nanofibers were first produced by electrospinning, and their surface was chemically functionalized using a simple aminolysis process. The capacity of the resulting material to adsorb Pb(II) from synthetic solutions was evaluated as a function of the contact time, pH, and initial metal ion concentration. The adsorbent system presented a quick kinetic adsorption, reaching an extremely high maximum adsorption capacity of about 50 millimol (mmol) of Pb(II) per gram of adsorbent system after just 30 min. Moreover, the effect of competing metal ions, such as Ni(II), Cd(II) and Cu(II), was studied at different molar ratios. Finally, when tested in continuous flow mode, aminated PET (APET) nanofibers were able to remove 97% of Pb(II) ions in solution, demonstrating their potential for the remediation of heavy metal-contaminated water.

Advances in organic-inorganic hybrid sorbents for the extraction of organic and inorganic pollutants in different types of food and environmental samples

The efficiency of the extraction and removal of pollutants from food and the environment has been an important issue in analytical science. By incorporating inorganic species into an organic matrix, a new material known as an organic-inorganic hybrid material is formed. As it possesses high selectivity, permeability, and mechanical and chemical stabilities, organic-inorganic hybrid materials constitute an emerging research field and have become popular to serve as sorbents in various separaton science methods. Here, we review recent significant advances in analytical solid-phase extraction employing organic-inorganic composite/nanocomposite sorbents for the extraction of organic and inorganic pollutants from various types of food and environmental matrices. The physicochemical characteristics, extraction properties, and analytical performances of sorbents are discussed; including morphology and surface characteristics, types of functional groups, interaction mechanism, selectivity and sensitivity, accuracy, and regeneration abilities. Organic-inorganic hybrid sorbents combined with extraction techniques are highly promising for sample preparation of various food and environmental matrixes with analytes at trace levels.

Nanofibers mat-based solid-phase extraction method for the pretreatment of urine samples and its application in the primary study on the disposition of nonylphenol after long-term low-level exposure in rats

A method was established for the analysis of nonylphenol (NP) in rat urine samples based on a solid-phase extraction (SPE) procedure with an amino functionalized polyacrylonitrile nanofibers mat (NH₂-PAN NF_SM) as sorbent coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The calibration curves prepared in three different days showed good linearity over a wide range of NP concentrations from 0.1 to 100.0ng/mL. It was remarkable that the proposed NH₂-PAN NFsM based SPE method showed superior extraction efficiency with the consumption of only 4mg of sorbent and 500μL of eluent. The eluent without any further concentration was directly analyzed by HPLC-MS/MS. As a result, a simple and effective sample preparation was achieved. In addition, the notable lower detection limit (LOD) of 0.03ng/mL revealed the excellent sensitivity of the proposed method in comparison with that in literatures. The recoveries ranged from 85.0% to 114.8% with the relative standard deviations (RSDs) ranging from 7.5% to 13.7%, which were better than or comparable to those from the published methods, suggesting high accuracy of the proposed method. The proposed method was applied in primary study on the disposition of nonylphenol after long-term low-level exposure in rats, providing information for health risk assessment on the real scenarios of NP exposure. NH₂-PAN NFsM shows great potential as a novel SPE sorbent for the analysis of biological samples.