Pipette-tip Solid-phase Extraction Research Articles

The Application of Pipette-Tip and Magnetic Dummy-Template Molecularly Imprinted Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography with Diode Array and Spectrofluorimetric Detection for the Determination of Coumarins in Cosmetic Samples

In this study, adsorbents based on molecularly imprinted polymers (MIPs) in two solid-phase extraction application forms, pipette tip and magnetic extraction, were used for the selective extraction of coumarins. The pipette-tip solid-phase extraction reduced solvent volumes; the magnetic MIP extraction was simple and effective for phase separation. Parameters affecting extraction, such as the amount of adsorbent, type of washing solvent, volume of the elution solvent, and extraction times for magnetic extraction, were optimized. The MIP-based adsorbents displayed high selectivity and extraction efficiency, resulting in recoveries ranging from 70.3 to 102.0% (RSD % less than 5.5%) for five coumarins under study, 6,7-dihydroxycoumarin-6-β-D-glucoside, coumarin, 7-methoxycoumarin, 6-methylcoumarin, and dicoumarol. The extracts were analyzed by high-performance liquid chromatography with diode array (DAD) and fluorescence (FLD) detectors, reaching limits of quantification of 0.5 and 0.9 µg·mL−1 for coumarin and dicoumarol detected by DAD and 0.001–0.012 µg·mL−1 for the other prohibited simple coumarins when used as a fragrance (detected by FLD). The proposed method was validated and its applicability was shown for the analysis of cosmetic samples like shower gel and perfume.

Determination of alectinib and its active metabolite in plasma by pipette-tip solid-phase extraction using porous polydopamine graphene oxide adsorbent coupled with high-performance liquid chromatography-ultraviolet detection

Alectinib is known as an effective targeted drug, which has excellent therapeutic effect on non-small cell lung cancer and can significantly prolong the survival of patients. Therapeutic drug monitoring is necessary due to the photo-instability of alectinib and the individual differences in patients. In this work, a porous polydopamine graphene oxide composite (PDAG) was prepared by a simple surface modification method. A PDAG-based pipette-tip solid-phase extraction (PT-SPE) coupled with HPLC-UV detection was proposed for the separation and detection of alectinib and its active metabolite M4 in plasma. The method was methodologically validated and showed good linearity in the range of 50–5000 ng mL−1 (R2 > 0.9995). The limit of detection (LOD) was 4.8 ng mL−1 and 3.9 ng mL−1 for alectinib and M4, respectively, and the limit of quantitation (LOQ) was 16.1 ng mL−1 and 13.1 ng mL−1, respectively. The intra-day and inter-day precision expressed by coefficient of variation was less than 4.8 %. The recovery of this method ranged from 84.9 % to 103.5 % with a standard deviation of less than 4.3 %. In conclusion, the established method is accurate, stable and inexpensive, and can be used to monitor the levels of alectinib and M4 in plasma, which provide technical and data support for exploring optimal individualized remedial dosing regimens.

Adaptive polarity of graphene oxide anchored silica doped with C18 for effective enrichment of aflatoxins from foodstuff

Selecting adsorbent with appropriate polarity is a practicable way to improve the enrichment efficiency for aflatoxins (AFs) during the solid phase extraction in sample pretreatment. In this study, graphene oxide anchored silica was prepared and applied to dop with C18 with suitable polarity for effective pre-concentration and purification of AFs from foodstuff. With systematic optimizing, GO anchored silica/C18 (1/1, w/w) exhibited excellent extraction performance for AFs. As the medium, a facile and efficient pipette-tip solid-phase extraction (PT-SPE) technique was developed for enrichment of AFs. Coupling with high-performance liquid chromatography fluorescence detection (HPLC-FLD), the developed analysis method illustrated the lower limits of detection of 0.075 ng/g and 0.17 ng/g for AFG2, AFB2 and AFG1, AFB1 (R2 > 0.99). The recoveries were calculated as 71.27 ∼ 94.52 % for the spiking level of 1, 5, and 20 ng/g with the intra-day and inter-day precision of 1.30 to 4.01 and 3.56 to 5.78, respectively. Hence, the developed PT-SPE-HPLC-FLD determination method was sensitive, accurate, and convenient for quantitative analysis of AFs at trace contents in foodstuff.

Mechanochemical synthesis ionic covalent organic frameworks/cotton composites for pipette tip solid-phase extraction of domoic acid in seafood

Pipette tip solid-phase extraction (PT-SPE) as a miniaturized solid-phase extraction technique have a wide range of applications in the field of sample pretreatment. In this study, ionic covalent organic frameworks@cotton (iCOF@cotton) were facilely synthesized by mechanochemical grinding method only in half an hour, and used as the adsorbents of PT-SPE. The synthesized iCOF@cotton not only had high specific surface area, suitable pore structure and cationic charge groups of iCOF that can extract polar targets quickly, but also reduced the problem of high back pressure of PT-SPE by the addition of cotton, thus accelerating extraction time. Combined with high performance liquid chromatographic tandem mass spectrometry (HPLC-MS/MS), an efficient and sensitive method was established for detection of domoic acid (DA, a toxin produced by algae). Under the optimal conditions, the proposed analysis method displayed excellent analytical performance, including broad range of linearity (10–1000 pg mL−1), low limit of detection (LOD, 5 pg mL−1), high correlation coefficient (0.9993), satisfactory precision (RSDs ≤6.4 %). In addition, the developed method was applied to the detection of DA in marine samples, and detected trace DA (18.6 pg mL−1) with satisfactory recovery (85.7%–107.2 %). The above results indicated that the prepared iCOF@cotton have great potential as the adsorbents for PT-SPE.

Simultaneous determination of three biomarkers of non-small cells lung cancer in urine by pipette-tip solid-phase extraction coupled with liquid chromatography tandem mass spectrometry

Simultaneous determination of multiple biomarkers can improve the effectiveness and accuracy of cancer diagnosis. Cortisol, cortisone, and 4-methoxyphenylacetic acid (4-Me) are metabolic biomarker group with high specificity and sensitivity for the diagnosis of non-small cells lung cancer (NSCLC), and the development of their simultaneous determination method is desired. Herein, a simple, sensitive, and low-cost method involving pipette-tip solid-phase extraction (PT-SPE) using anion exchange adsorbent (MAX) coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed for the simultaneous determination of three biomarkers (cortisol, cortisone, and 4-Me) in human urine. The sample (0.1 mL), adsorbent (1.5 mg) and organic reagent (3.5 mL) of MAX-PT-SPE are less consumed, and have the advantages of easy access to raw materials, simple assembly, convenient on-site instant extraction, low pollution, and low cost. The limits of detection of the three biomarkers were 0.006-0.024 ng mL-1, the recoveries of three spiked levels (2, 50, and 500 ng mL-1) were 91.0%-99.3%, with the relative standard deviations (RSDs) ≤ 5.9%. Finally, the MAX-PT-SPE-LC-MS/MS method achieved the quantitative analysis of cortisol, cortisone, and 4-Me in urine of different patients of NSCLC. This method is expected to be used in the non-invasive auxiliary diagnosis of NSCLC, and it provides a new strategy for multi-molecular diagnosis and multi-omics combined diagnosis.

Preparation and evaluation of a tryptophan based hypercrosslinked porous polymer as an efficient adsorbent for pipette tip solid-phase extraction of sulfonamides

A novel tryptophan-based porous polymer is designed and synthesized via a facile one-step hypercrosslinking polymerization process, and applied as sorbent for extraction of trace sulfonamides in foodstuffs. The developed polymer has high surface area, large conjugate system, and abundant functional groups (e.g., π-π stacking, hydrogen bonding, hydrophobic and electrostatic attraction interactions), which endow it with superior affinity and high adsorption capacity for sulfonamides (16.16–59.29 mg g−1). The optimized SPE method is coupled with HPLC-DAD to create a sensitive and efficient protocol that provides good linearity (R2 ≥ 0.9979), low limits of detection, satisfactory recoveries (92.5–109.5 %) and high precisions (RSDs < 8.24). In addition, the newly proposed method greatly reduces the amount of adsorbent (2.0 mg) and organic solvent (2.0 mL) used. Adsorption kinetics, isotherms, and simulation calculations studies further reveal the presence of monolayer adsorption, chemical adsorption process, and multiple interactions. Thus, this work presents a polymer capable of multiple interactions for the pretreatment of trace sulfonamides in foodstuffs.

Metal-organic frameworks modified melamine foam in pipette-tip for rapid solid-phase extraction of organophosphorus pesticides in fruits and vegetables.

In this work, metal-organic frameworks (MOFs) including Fe-MIL-101 and Ti-MIL-125 were prepared and fixed on the melamine foam (MF) by polyvinylidene fluoride (PVDF) to prepare MF/PVDF/MOFs, which was used as adsorbents in pipette-tip solid-phase extraction (PT-SPE) for rapid extraction of organophosphorus pesticides (OPPs). Then, a gas chromatograph-flame thermionic detector (GC-FTD) was used for simultaneous analysis of Dimethoate (DMT), Iprobenfos (IBF), Parathion-methyl (PAM), and Chlorpyrifos (CPF). The morphology, crystal structure, and functional groups of MF/PVDF/MOFs were characterized, indicating that Ti-MIL-125 and Fe-MIL-101 were successfully synthesized and distributed on MF. The Fe-MIL-101 and Ti-MIL-125 showed good extraction ability for OPPs, which was mainly due to the π-π interaction and the multiple porous structures. Under the optimal conditions, the limit of detection (LODs) of four OPPs was 0.03-0.14μg L-1 and the RSDs were less than 9.9%. The developed PT-SPE method showed a short extraction time (<3min). The recoveries in fruits and vegetables (Celery, cabbages, and oranges) ranged from 75.3%-118.8% (RSDs<9.6%). The prepared MF/PVDF/MOFs demonstrated the efficient extraction performance of OPPs, contributing to the rapid pretreatment of OPPs from food and the environment.

Synthesis of azo-linked covalent organic polymers for pipette tip solid-phase extraction of sedative residues from animal tissues samples.

Azo-linked covalent organic polymers (ACOPs) were synthesized by a simple azo reaction, with 2,2'-bis(trifluoromethyl)benzidine and 1,3,5-trihydroxybenzene as the monomers. The preparation process was mild, green, and environmental-friendly, avoiding the use of high temperature, metal catalysis, and harmful organic reagent. The obtained ACOPs were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and Brunauer-Emmett-Teller. With the prepared ACOPs as adsorbent, a method of pipette tip solid-phase extraction-liquid chromatography-tandem mass spectrometry detection (PTSPE-LC-MS/MS) was proposed for the analysis of target sedatives in animal tissues. Furthermore, the parameters for the extraction of five sedatives, including the amount of adsorbent, pH value, ion strength, elution solvent and volume, were investigated. Under the optimized conditions, the linear dynamic range was found from 0.1 to 10.0μg kg-1, and the limits of detection were ranged from 0.02 to 0.1μg kg-1. The method was assessed by the analysis of target sedatives in animal tissues, and the recoveries for the spiked pork muscle and pork liver samples were 84-102% and 83-101%, respectively. The results show that the developed method of PTSPE-LC-MS/MS with ACOPs as adsorbent is efficient for the analysis of trace sedatives in animal tissues.

Determination of Benzimidazoles in Chicken and Egg Samples by Urea-Based Covalent Organic Polymer (UCOP) Pipette Tip–Solid-Phase Extraction (PT–SPE) and High-Performance Liquid Chromatography–Tandem Mass Spectrometry (HPLC–MS)

A urea-based covalent organic polymer (UCOP), was synthesized using 1,4-phenylene diisocyanate (PPDI) and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl) trianiline (TTTA) and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nitrogen adsorption-desorption isotherm analysis. The prepared material was employed as an adsorbent for pipette tip–solid-phase extraction (PT–SPE) for benzimidazoles before high-performance liquid chromatography–tandem mass spectrometry analysis (HPLC–MS). The parameters affecting the isolation efficiency, including salt concentration, sample pH, mass of adsorbent, and types and volumes of eluent, were optimized. Using these conditions, PT–SPE provided good linearity from 0.1 to 10 μg kg−1 with low limits of detections (LODs) of 0.02 μg kg−1 together with good precision (relative standard deviations from 4.2 to 8.3%) and accuracy (recoveries from 76.2 to 84.8%). The results demonstrate that the urea-based covalent organic polymer has the potential for the enrichment of trace benzimidazoles.

Preparation of acidity-sensitive N-isopropylacrylamide and methacrylic acid copolymer monolithic column for the pipette tip solid phase extraction of phenols

An acidity-sensitive poly(N-isopropylacrylamide-methyl acrylic acid-co-divinyl- benzene) monolith was prepared in situ in a pipette tip for solid phase extraction of phenol, m-cresol, o-nitrophenol, 2,4-dichlorophenol and p-tert-butylphenol. The monolith was characterized by FT-IR, BET (surface area = 266.56 m2/g) and thermogravimetric analysis (thermally stable up to 350 °C). The introduction of methyl acrylic acid enhanced the stability in the strong alkaline condition. The adsorption experiments and density function theory calculations indicated NIPAM was the main adsorption sites and the adsorption mechanism of phenol on the monolith was hydrophobic interaction, H-bond interaction, C − H···π interaction of isopropyl group of NIPAM with the phenyl group of phenols. Based on these features and under the optimal extraction conditions, a pipette tip solid phase extraction coupled to high-performance liquid chromatography with ultraviolet detection method was developed for the determination of 5 phenols in the diffusion of polycarbonate cups. Due to the usage of 0.1 M NaOH as the eluent, the method presented selectivity for phenols based on the acidity-sensitive of the monolith. Wide linear range (0.6–200 µg/L), low detection limits (0.2–0.3 µg/L), good reproducibility (%RSD less than 9.8%) and satisfactory recoveries (86.3–114.1%) were obtained. The proposed method was suitable for quantitative analysis of phenollic in water samples.

Deep eutectic solvent loaded onto graphene oxide as a novel phase for pipette-tip micro-solid phase extraction of levofloxacin from seawater and body fluid samples

ABSTRACT In this research, applicability of an environmentally friendly deep eutectic solvent (DES) for pipette-tip micro-solid phase extraction and preconcentration of levofloxacin prior to its quantification by spectrophotometry at the wavelength of 240 nm is presented. Carvone:thymol (1:1 molar ratio) DES was prepared and coated on graphene oxide and applied as adsorbent. This adsorbent was characterised utilising Fourier transform infrared and field emission scanning electron microscopy, which showed a uniform layer of DES coated on graphene oxide. 5.0 mg of this adsorbent was packed into a 100 µL pipette-tip and was applied to miniaturised pipette-tip solid-phase extraction of levofloxacin. Parameters affecting microextraction including kind and volume of elution solvent, pH, amount of sorbent, sample volume, and number of aspirating/dispensing cycles were investigated and optimised using one-variable-at-a-time procedure, central composite design, and Box-Behnken design response surface methodologies. The developed method required only 5.0 mg of adsorbent and 150 µL of methanol:acetone (2:1) (elution solvent) to achieve a low detection limit of 0.3 µg/L with a linear range of 1–500 µg/L. High enrichment factor of 65.3 with a good precision (RSD ≤ 4.7%) was also achieved. The proposed method was successfully applied to determine levofloxacin in pills, blood, urine and a few seawater samples.

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.

Preparation of wax-based molecularly imprinted monolith for pipette-tip solid-phase extraction: a hybrid method.

The development of molecularly imprinted monolith (MIM) for pipette-tip solid-phase extraction (PT-SPE) forsample pretreatmentis challenging. In this work, a wax-based molecularly imprinted monolith (WMIM) was successfully prepared with a hybrid method by integration of the traditional packing SPE column and MIM, including preparation of the salt column inside the pipette, polymerization of wax-based imprinted column (WIC) outside the pipette, and immobilization of WIC inside the pipette tip. To ensure the penetration of samples and solvents during the PT-SPE, micrometer-range interconnected macropores were tailor-made via the salt-template sacrifice method. Forthe production of high affinity imprinted sites within the WIC, octadecanoic acid was used as functional monomer in the paraffin matrix. In terms of the adsorption property, the synthesized WIC exhibited a specific affinity to cardiovascular drugs, with an imprinting factor (IF) of 4.8 for the target analyte. Moreover, the WMIM-based PT-SPE was coupled with fluorescence spectrophotometry for the target propranolol determination (the excitation and emission wavelengths were 294nm and 343nm, respectively). This analytical method showed high recovery of target detection in different real samples (R > 90%), good sensitivity, and accuracy (R2 = 0.99, LOD = 0.03ngmL-1). We believe this work could provide a significant contribution for the fabrication of MIM and promote an emerging trend of developing elution-free materials for sample pretreatment.

Migration detection of six aromatic amines in polyamide food contact materials by HPLC after molecularly imprinted polymer pipette tip solid phase extraction

Some food contact materials (FCMs) may contain aromatic amines (AAs), which would migrate to food and pose a serious threat to human health. An extraction and determination method for AAs was established using pipette tip solid-phase extraction (PTSPE) combined with high performance liquid chromatography-photodiode array detector (HPLC-PAD). The PTSPE was based on molecularly imprinted polymer (MIP) monolith, which was synthesized in situ polymerization using benzidine as template molecule and 4-vinylpyridine as functional monomer. It was applied for selective extraction of six AAs from FCMs, including benzidine, 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 2-methoxy-5-methylaniline, 3,3′-dimethoxybenzidine, 4,4′-methylenedianiline and 4-aminobiphenyl. The MIP monolith showed highly specific recognition and good adsorption ability for the six AAs, the imprinting factor for 4,4′-methylenedianiline can reach 4.29 and the adsorption capacity for 4-aminobiphenyl can reach 112.3 mg g−1. The linear range of the determination method for the six AAs was 0.60–500 µg kg−1 (R2＞0.997), the limits of quantitation was 0.60–4.50 µg kg−1 and the limits of detection (S/N = 3) was 0.20–1.50 µg kg−1. The MIP-PTSPE-HPLC-PAD method was applied for the migration detection of six AAs from polyamide kitchenware and the absolute recovery were 81.7–110.9%.

Dual-template hydrophilic imprinted resin as an adsorbent for highly selective simultaneous extraction and determination of multiple trace plant growth regulators in red wine samples

In recent years, numerous plant growth regulators have been found in foods and have a toxicity to human health, so its simultaneous multiple monitoring is urgently. For the first time, a rapid, accurate, and high-selective method was established to extract and determine multiple plant growth regulators simultaneously in red wines using a new dual-template hydrophilic molecularly imprinted resin (DHMIR) as an adsorbent of pipette tip solid-phase extraction coupled with HPLC. The as-prepared DHMIR combined the advantages of the hydrophilicity of hydrophilic resin and multi-imprinted recognition of dual-template molecular imprinting, overcoming the poor imprinted recognition ability of traditional imprinting materials in water and low extraction efficiency to multiple targets. Under the optimized conditions, the proposed method exhibited high sensitivity (2.29–3.94 ng mL−1) and recoveries (80.9–109.0 %) using only 15 mg DHMIR. This study provides an effective strategy for rapid, accurate, low-cost, and high-selective determination of the multiple analytes in food samples.

Recent Advances in Molecularly Imprinted Polymers for Antibiotic Analysis.

The abuse and residues of antibiotics have a great impact on the environment and organisms, and their determination has become very important. Due to their low contents, varieties and complex matrices, effective recognition, separation and enrichment are usually required prior to determination. Molecularly imprinted polymers (MIPs), a kind of highly selective polymer prepared via molecular imprinting technology (MIT), are used widely in the analytical detection of antibiotics, as adsorbents of solid-phase extraction (SPE) and as recognition elements of sensors. Herein, recent advances in MIPs for antibiotic residue analysis are reviewed. Firstly, several new preparation techniques of MIPs for detecting antibiotics are briefly introduced, including surface imprinting, nanoimprinting, living/controlled radical polymerization, and multi-template imprinting, multi-functional monomer imprinting and dummy template imprinting. Secondly, several SPE modes based on MIPs are summarized, namely packed SPE, magnetic SPE, dispersive SPE, matrix solid-phase dispersive extraction, solid-phase microextraction, stir-bar sorptive extraction and pipette-tip SPE. Thirdly, the basic principles of MIP-based sensors and three sensing modes, including electrochemical sensing, optical sensing and mass sensing, are also outlined. Fourthly, the research progress on molecularly imprinted SPEs (MISPEs) and MIP-based electrochemical/optical/mass sensors for the detection of various antibiotic residues in environmental and food samples since 2018 are comprehensively reviewed, including sulfonamides, quinolones, β-lactams and so on. Finally, the preparation and application prospects of MIPs for detecting antibiotics are outlined.

Restricted access polypyrrole employed in pipette-tip solid-phase extraction for determination of nimodipine and nicardipine in breast milk.

A HPLC-UV method for the determination of nimodipine and nicardipine in breast milk using restricted access polypyrrole as an adsorbent in pipette-tip solid-phase extraction (PT-SPE) has been developed. The chromatographic conditions were a C18 column (150 mm × 4.60 mm, 5 μm) using methanol : acetonitrile : ultrapure water (55 : 30 : 15, v/v/v) at a flow rate of 1.0 mL min-1 and detection at 236 nm. The adsorbents have been synthesized and characterized by using Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, surface analysis, wettability and point zero charge, and were then applied in sample preparation. The main parameters that affect analyte recovery from breast milk by PT-SPE were optimized and the analytical method showed recoveries around 100%, linearity from 3 to 3000 ng mL-1, and correlation coefficients (r) ≥ 0.99 for the two analytes, in addition to adequate precision, accuracy and robustness. Finally, the validated method has been successfully applied in analyses of breast milk from volunteers.

Ti4+ modified melamine foam in the pipette tip for effective solid-phase extraction of glyphosate in aqueous samples

Glyphosate, a widely used herbicide, is prone to residue in the environment that may cause harm to humans. In this work, titanium ion-modified melamine foams (MF/PDA/Ti4+) were prepared as sorbents to achieve rapid extraction of glyphosate by pipette-tip solid-phase extraction (PTSPE). The MF/PDA/Ti4+ was characterized by SEM, EDS, XPS, and TGA, and its adsorption properties were evaluated by adsorption kinetics and isotherm experiments. The porous structure and good mechanical properties of MF made the MF/PDA/Ti4+ fill into the pipette-tip easily and could achieve low back pressure. The developed PTSPE method showcased short extraction time (<2 min) for glyphosate and the limits of detection (LOD, 3σ/k) was 4.9 μg/L. It was applied in aqueous samples (tap water, lake water, tea drink, and orange juice) with recoveries ranging from 82.8 % to 108.2 % and the relative standard deviation (RSD, n = 3) was less than 7.7 %, demonstrating broad perspectives on the extraction of glyphosate from the aquatic and terrestrial environment.

Novel covalent organic frameworks based electrospun composite nanofiber membranes as pipette-tip strong anion exchange sorbent for determination of inorganic arsenic in rice

Novel covalent organic frameworks (COFs) based PAN@TpBD(NH2)2 electrospun composite nanofiber membranes (ECNMs) were fabricated as strong anion exchange sorbent by implementing electrospinning technology. The finished sorbent was characterized, and key parameters of pipette-tip solid phase extraction (PTSPE) procedures were investigated. Inorganic arsenic (iAs) was successfully separated from rice under the optimal precondition conditions, and quantified by hydride generation-atomic fluorescence spectrometry (HG-AFS). This PTSPE-HG-AFS methodology achieved 0.015 μg L-1 detection limit, 4.67 % relative standard deviation, and 86.48～99.11 % recoveries. In this work, preparation and characterization of this novel COFs-based anion exchange sorbent, PAN@TpBD(NH2)2 ECNMs, is described and its suitability for PTSPE applications is demonstrated.

Carbonized metal-organic framework-74/carbon aerogel composites for the efficient extraction of triazole fungicides from fruits and vegetables

To improve the extraction efficiency, availability, and stability of metal-organic framework (MOF) for pipette-tip solid-phase extraction (PT-SPE), a carbonized MOF-74/carbon aerogel composite (CMOF-74/CA) was developed. A carbon aerogel with a surface area of 547.7 m2 g−1 was prepared by carbonizing a watermelon peel. After that, via a hydrothermal reaction, the MOF-74 was in situ grown on the surface. After the pyrolysis at 700 °C for 2 h, the CMOF-74/CA composite was obtained. Through regulating the concentration of reactants, a series of MOF-74/CA and CMOF-74/CA materials were prepared. These materials were used to extract hexaconazole and diniconazole in fruits and vegetables before gas chromatography-flame ionization detection (GC-FID). The adsorbent type and amount, sample pH, and the desorption solvent type and volume were optimized factor by factor. Under the optimized conditions, a PT-SPE-GC-FID method was established. Moreover, good linearity in the concentration ranges of 0.098–200.0 mg kg−1 and 0.196–200.0 mg kg−1, and detection limits ranging between 0.033 and 0.065 mg kg−1 were achieved for two triazole fungicides (TFs). The relative standard deviations (n = 3) for intra-day and inter-day tests were in the ranges of 3.1–3.2% and 3.0–3.4%, respectively. The method showed satisfactory analytical performance in different samples with good relative recoveries in the range of 72.6–116%. Compared with some methods, it displayed wider linearity, better or comparable sensitivity, and enhanced analytical precision.