Solid-phase Extraction Adsorbent Research Articles

Methylated magnetic covalent organic framework for sample preparation and LC-MS/MS detection of 12 tadalafil analogs in dietary supplements

Tadalafil analogs are often illegally added to dietary supplements such as herbal beverages, protein powders and tablet foods. Due to the complexity of the matrices, effective extraction of tadalafil analogs is the key to achieve accurate quantification. Therefore, it is of great significance to establish a rapid and effective method for the analytical determination of tadalafil analogs in complex matrices. In this study, a novel methylated magnetic covalent organic framework, Fe3O4@TFPB-OT, was successfully synthesized under mild conditions. Fe3O4@TFPB-OT demonstrated robust adsorption capabilities, with capacities ranging from 52.4 to 90.9 mg/g for the tadalafil analogs. Several pre-enrichment parameters were optimized, including adsorbent dosage, extraction time, pH, shaking time, elution solvent, and desorption time. The applicability of Fe3O4@TFPB-OT was evaluated as effective adsorbents for the magnetic solid-phase extraction (MSPE) of 12 tadalafil analogs in dietary supplements. Combined with high-performance liquid chromatography-tandem mass spectrometry, the limits of detection (LODs) of this method ranged from 0.005 to 0.05 μg/L in liquid matrices and from 0.005 to 0.05 μg/kg in solid matrices, showing good sensitivity and recoveries ranged from 56.1 % to 90.9 %with relative standard deviations lower than 3.9 %, demonstrating good accuracy and precision. Additionally, the adsorbent retained its effectiveness after at least ten reuse cycles, indicating significant reusability. This study provides an effective method for the analysis and detection of tadalafil analogs in dietary supplements and has great potential for application.

Solid phase extraction-surface enhanced Raman spectroscopy (SPE-SERS) test of antibiotic residues in Milk based on au@ MIL-101 NPs

A SPE-SERS method was developed for the detection of several antibiotic residues in dairy products. Gold nanoparticles (Au NPs) encapsulated with an ultrathin Cr-MIL-101 shell (Au@Cr-MIL-101 NPs) have been synthesized, and the thickness of Cr-MIL-101 shell can be precisely controlled to 3 nm. As a superior solid phase extraction (SPE) adsorbent, Cr-MIL-101 acts as a shell layer to effectively enrich antibiotics within the localized surface plasmon resonance (LSPR) field of Au NPs, which enhances the SERS signal and eliminates background interference. The method can achieve highly sensitive and high-throughput detection for tetracycline hydrochloride, sulfapyridine and benzylpenicillin sodium in dairy products, and the detection limits (LOD) are as low as 2.237, 2.644 and 4.662 ppb respectively. The recoveries of antibiotic residues in spiked dairy products ranged from 72.31 % to 146.7 % with matrix effects (ME) of −15.13 % to 28.68 %. Thus, this method holds significant promise for rapid detection of antibiotics in milk.

Extraction of methamphetamine and pseudoephedrine by modified graphene oxide solid phase extraction method coupled to HPLC-UV in urine sample.

Methamphetamine, pseudoephedrine, and related drugs are among the first drugs used for the stimulation of the central nervous system. In this study, two adsorbents based on graphene oxide (GO) were synthesized and used for the analysis of methamphetamine and pseudoephedrine. The prepared nano-adsorbents based on GO in this study were coated by polyaniline (PANI) and Fe3O4/C-nanodot/GO (magnetic adsorbent). The average size of nanoparticles (GO/PANI) was 18.43nm. The specific surface area and pore size diameter of Fe3O4/C-nanodot/GO were 22.71 m2 g- 1 and 15.23nm, respectively. Experimental variables affecting the extraction efficiency of the analytes such as pH of the sample solution, amount of adsorbent, extraction time, and type of eluents were investigated and optimized by response surface methodology. Under optimum conditions, GO/PANI and Fe3O4/C-nanodot/GO were considered appropriate solid phase extraction adsorbents for HPLC-based analyses of the studied drugs in human urine samples. However, GO/Fe3O4 nano adsorbent (Fe3O4/C-nanodot/GO) showed superior working condition than GO/PANI. The validated proposed analytical methods can be used for the quantitative determination of methamphetamine and pseudoephedrine in actual samples.

Cost-effective synthesis and application of Cu²⁺-doped melamine formaldehyde resin for enhanced tetracycline enrichment in environmental water

Tetracycline antibiotics (TCs) are typically present at low residue levels in environmental water, necessitating enrichment prior to analysis. In this study, a Cu2+-doped melamine formaldehyde resin (Cu-MFR) was synthesized to enhance the adsorption efficiency for TCs, leveraging the formation of stable Cu2+-TC complexes on the sorbent surface. Then it was used as an adsorbent in solid-phase extraction (SPE) for the enrichment of four TCs from water samples. The optimized parameters for Cu-MFR in the analysis of TCs in environmental water enabled linear detection ranges from 0.20 to 50 ng/mL, with relative recoveries ranging from 79.5 % to 97.6 % and relative standard deviations ≤ 10.0 %, using high-performance liquid chromatography-tandem high-resolution mass spectrometry (HPLC-HRMS). The limits of detection for the four TCs were determined to be between 0.11 and 0.16 ng/mL, indicating its potential for practical application in real sample analysis.

Highly sensitive detection of organophosphorus pesticides in water using a carboxyl-functionalized magnetic covalent organic framework

The development of novel methods for the precise quantification of organophosphate pesticides (OPPs), with enhanced accuracy, sensitivity, and efficiency, is crucial for environmental monitoring and human health risk assessment. In this study, Fe3O4@SiO2@COF-COOH magnetic core–shell nanoparticles were synthesized by coating a carboxyl-functionalized covalent organic framework (COF-COOH) onto the surface of amino-modified silica-coated iron(III) oxide particles (Fe3O4@SiO2-NH2). The incorporation of carboxyl groups, covalent organic framework and magnetic properties imparted superior performance to the adsorbent in magnetic solid-phase extraction (MSPE) of polar compounds from complex sample matrices. An analytical method based on Fe3O4@SiO2@COF-COOH coupled with GC–MS/MS was developed for the determination of eight organophosphate pesticide residues in river water near farmland. The established method displays good linearity in the range of 0.1–500 ng/mL for four OPPs and 1–2000 ng/mL for the other four, with correlation coefficients between 0.9903–0.9983. The LODs (S/N = 3) and LOQs (S/N = 10) were determined to be in the ranges of 0.53–9.6 ng/L and 1.8–31.9 ng/L, respectively. The adsorption mechanism was characterized by density functional theory calculations. Furthermore, the established method was successfully applied to analyze the distribution of trace OPPs in real river water samples collected from various cities in Henan Province. Its rapid, straightforward, and efficient ability to enrich trace levels of OPPs from complex real-world samples makes it a valuable tool for environmental monitoring, food safety, and human health management.

Enhanced Pb(II) extraction using a novel chitosan/pectin/carbon composite adsorbent for solid-phase extraction

ABSTRACT This research aimed to present the development of chitosan/pectin/carbon (CPC) materials as adsorbents in the solid-phase extraction (SPE) of Pb(II) from river water samples. The CPC adsorbent shows active groups effectively binding Pb(II) ions. The characterisation included using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDX) to analyse functional groups and evaluate surface morphology with elemental composition. SPE parameters were systematically optimised to enhance adsorption-desorption efficiency, including pH 4.0, Pb(II) concentration of 5 mg L−1, flow rate of 13.3 mL min−1, elution flow rate of 12.8 mL/min using nitric acid (HNO3), a sample volume of 25 mL, eluent volume of 1 mL and concentration at 1.0 M. The results showed that the implementation of the refined CPC-based SPE method for Pb(II) analysis in water samples obtained a recovery range of 101% to 103%, accompanied by a significant 25-fold concentration enrichment of Pb(II). Moreover, the adsorption concentration increased from undetectable levels to 1.27–2.48 mg L−1, reporting the efficacy of the CPC-based SPE method for sensitive and accurate Pb(II) analysis in environmental samples.

Highly selective guanidine-linked covalent organic framework for efficient removal of perfluoroalkyl carboxylic acids from water samples

In this study, guanidine-linked covalent organic framework (TPDGCl) was synthesized via a solvothermal method. The presence of guanidine groups in its structure facilitates electrostatic interactions and provides hydrogen bonding sites, enabling the selective enrichment of perfluoroalkyl carboxylic acids (PFCAs) from environmental water samples. The material exhibits rapid kinetic mass transfer, which facilitates the efficient removal of samples containing PFCAs from aqueous solutions within 5 min. Furthermore, TPDGCl exhibits several advantageous properties, including high selectivity for PFCAs, a high adsorption capacity (2005 mg/g), excellent chemical stability, and remarkable recyclability (five cycles). Additionally, density functional theory (DFT) studies have demonstrated that the adsorption of PFCAs on TPDGCl is enhanced by ion exchange, hydrophobic interactions, hydrogen bonding interactions and ordered channel structures. Finally, TPDGCl was used as an adsorbent for dispersive solid-phase extraction (d-SPE), in combination with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), to develop an analytical method for the efficient extraction and sensitive detection of PFCAs. The developed method exhibits highly sensitivity, with detection and quantification limits of 0.64–0.85 ng/L and 2.6–3.4 ng/L, respectively. The recoveries of actual water samples ranged from 75.4% to 113.7%. Moreover, TPDGCl effectively reduces the levels of PFCAs in real water samples to less than 70 ng/L within only 1 h. These results indicate that TPDGCl is an effective adsorbent for removing PFCAs from environmental water samples.

A hierarchical porous Fe3O4-COOH@H-ZIF-67 composite as magnetic solid-phase extraction adsorbent for benzimidazole pesticides

A hierarchical porous structural magnetic zeolite imidazolate framework-67 composite (Fe3O4-COOH@H-ZIF-67) was prepared through directly mixing the H-ZIF-67 and glutaric anhydride functionalized Fe3O4 nanospheres, of which the H-ZIF-67 was synthesized through a double template pore size regulation method. The successful preparation of Fe3O4-COOH@H-ZIF-67 composite was confirmed based on the material characterization using different techniques. The prepared composite was applied in the efficient removal of four benzimidazole pesticides (BZDs) in water using magnetic solid-phase extraction (MSPE) process. The results of static and dynamic adsorption experiments indicate that the adsorption of BZDs on Fe3O4-COOH@H-ZIF-67 follow pseudo-second-order kinetics, the Langmuir model fitted well with the adsorption data (R2 are all higher than 0.9969), and the maximum adsorption capacity for BZDs are 7.44–31.11 mg/g. Meanwhile, the adsorption mechanism study indicate that both hydrogen bonding and coordination play important roles during the adsorption process of BZDs. Finally, the developed MSPE method was combined with HPLC analysis and applied in the removal of BZDs from simulated pesticides wastewater. The removal rate was 82.76–96.18 %, and the treated samples met the requirements of the maximum residue limits of CBZ in the national standard GB 21523–2008. In addition, the adsorbent can be used at least three times and the extraction efficiency changed within 3 % after being stored in dry atmosphere at room temperature for 90 days. The results of this work manifested that Fe3O4-COOH@H-ZIF-67 composite can be used for removal and analysis of BZDs in complex samples.

Preparation and evaluation of polymeric ionic liquid functionalized microparticles as the efficient adsorbent for pipette tip solid phase extraction of sulfonamides

Sulfonamides (SAs) residues are commonly found in environmental samples, which is highly concerning for public safety and environmental protection. The detection of SAs is quite important but challenging. In this work, a kind of polymeric ionic liquid functionalized microparticles (PIL-FM) was synthesized via a simple free radical polymerization reaction, and applied as the adsorbent for pipette tip solid phase extraction (PT-SPE) of three SAs from river water, milk powder and honey samples. The adsorption performance of PIL-FM on SAs were evaluated using adsorption kinetics and adsorption isotherms, and the results showed that PIL-FM had the best selectivity for SMZ with the maximum adsorption capacity was as high as 45.05 mg·g−1. The extraction process was optimized and the adsorption mechanism was preliminarily discussed. PIL-FM has the excellent selectivity for SAs mainly because of the strong π-π interaction, and the electrostatic repulsion between them in the elution step also has a positive impact. Under optimal conditions, combined with HPLC, this PT-SPE method had wide linearity (0.2–100 μg·L−1, R2 ≥ 0.9998) and low limits of detection (0.06–0.08 μg·L−1). The intra-day and inter-day repeatability were found to be 3.7 %–4.6 % and 4.5 %–6.2 %, respectively. The suggested PT-SPE method is simple, low cost, rapid, and efficient to extract SAs, and can be applied for the monitoring of SAs residues in the aquatic environment and in food.

Polypyrrole as Adsorbent in Magnetic Solid Phase Extraction for Progesterone Determination from Human Plasma.

A straightforward and effective chromatographic method has been created for the analysis of progesterone from human plasma using a composite based on polypyrrole/magnetic nanoparticles in the sample preparation procedure. The quantification of progesterone is necessary due to its importance in human development and fertility. The employed conditions used acetonitrile:ultrapure water (70:30, v/v) as the mobile phase at 1.0 mL min-1 and an octadecyl silane column (Phenomenex Gemini, 250 mm × 4.6 mm, 5 μm) at a wavelength of 235 nm. The composite and its precursors were synthesized and properly characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy/energy dispersive spectroscopy, thermogravimetric analysis, and point of zero charge. The main factors affecting the extraction recovery of progesterone from pool human plasma samples employing magnetic solid phase extraction have been studied, such as sample pH (without adjustment), sample volume (1000 μL), washing solvent (ultrapure water), eluent (acetonitrile), eluent volume (1000 μL), and amount of adsorbent (10 mg). The extraction recoveries ranged from 98% to 102%, and linearity ranged from 5 to 3000 ng mL-1. The correlation coefficient (r) was ≥0.99, and acceptable relative standard deviation (precision), relative error (accuracy), and p-values (robustness) were observed. Lastly, the plasma samples from pregnant women were successfully analyzed by the validated method.

Development of amphiphilic hypercrosslinked porous polymers for magnetic extraction of multiple environmental pollutants in water

Under the principle of similar compatibility, researchers have developed various polarity extractants corresponding to a class of chemicals. Separating different polarities chemicals with one extractant effectively has become a novel research trend in separation science. Given the complexity of environmental sample matrices and the significant differences in polarity and solubility of various compounds, the introduction of hydrophilic groups to hydrophobic material skeletons can lead to sorbents with hydrophilic-lipophilic balance (HLB) property and thus improve their extraction performance for substances with different polarities. In this work, a hypercrosslinked polymer (HCPPz-TPB), designated as HLB, was synthesized by incorporating polar pyrazine and nonpolar triphenylbenzene molecules within each other. Subsequently, a core-shell magnetic composite material was obtained by encapsulating magnetic Fe3O4 nanoparticles in HCPPz-TPB. The material was applied as an adsorbent for magnetic solid phase extraction (MSPE) and combined with a high-performance liquid chromatography-photodiode array detector (HPLC-PDA) to enrich, separate, and detect seven polar contaminants in environmental water samples. The proposed approach, Fe3O4@SiO2@HCPPz-TPB−MSPE-HPLC-PDA, is characterized by its outstanding high sensitivity, low detection limits, wide linear range, and good reproducibility. The method demonstrated satisfactory linearity in the range of 0.05–2 μg mL-1 with R2 values between 0.9969 and 0.9997; the limits of detection (LOD) were observed to be within the range of 0.0019–0.016 μg L-1, and limits of quantification (LOQ) was observed to be within the range of 0.0064–0.054 μg L-1 range with good precision. The recoveries of the different contaminants in the environmental samples ranged from 83.61 to 116.46% (RSD≤10.56, n = 5). The new hydrophilic-lipophilic balance extractant is highly efficient, sensitive, and precise for extracting different polar pollutants. The findings demonstrate that the Fe3O4@SiO2@HCPPz-TPB display a remarkable affinity for multiple targets, driven by complex interactions including multi-stackings and hydrogen bonding as a sorbent. The synthesized Fe3O4@SiO2@HCPPz-TPB may be employed in diverse applications, including extraction, removal, and determination of diverse trace multi-target analytes in complex media.

Surface amphiphilic hybrid porous polymers based on cage-like organosiloxanes for pipette tip solid-phase extraction of microcystins in water

The occurrence of microcystins (MCs) during harmful algal blooms (HABs) represents a major threat to freshwater environments. In this work, a novel surface amphiphilic hybrid porous polymers based on cage-like organosiloxanes (PCSs) was prepared for the enrichment of MCs. The copolymerization of bifunctional amphiphilic monomers, 2-methacryloyloxyethyl phosphorylcholine (MPC) and N-benzylquininium chloride (BQN), with the cross-linker methacryl substituted polyhedral oligomeric silsesquioxane (POSS) was achieved in an ionic liquid-based porogenic medium. The hierarchical porous structure, a variety of surface functional groups and weak hydrophilicity were well characterized on the prepared materials using scanning electron microscopy, nitrogen adsorption/desorption analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential analysis and water contact angle testing, respectively. The as-prepared surface amphiphilic PCSs was used as an adsorbent for pipette tip solid-phase extraction (PT-SPE) to enrich microcystins (MCs) from surface waters before their analysis by capillary electrochromatography (CEC) and liquid chromatography-mass spectrometry (LC-MS). Under the optimal conditions, the established PT-SPE-LC-MS method exhibited a wide linear range (10–10,000 ng L−1), low limits of detection (4.0–8.0 ng L−1) and satisfactory recoveries (89.5–102.8 %) for MCs. An adsorption mechanism involving electrostatic interactions, hydrogen bonding, hydrophilic interactions, and π-π stacking has been proposed. The findings suggest that the use of surface amphiphilic PCSs materials as adsorbents in the PT-SPE platform facilitates efficient enrichment of MCs for subsequent chromatographic analysis. These investigations offer a new perspective on the simple and uncomplicated pretreatment of complex environmental samples.

Preparation of Polydopamine-Based Electrospun Nanofibers as an Efficient Adsorbent for Solid-Phase Extraction of Trace Mycotoxins Followed by HPLC

Preparation of Polydopamine-Based Electrospun Nanofibers as an Efficient Adsorbent for Solid-Phase Extraction of Trace Mycotoxins Followed by HPLC

Preparation of an imidazolium-based poly(ionic liquid) functionalized magnetic three-dimensional graphene oxide for magnetic solid phase extraction of pyrethroids from tea samples

In this work, an imidazolium-based poly(ionic liquid) (poly(1-dodecyl-3-vinyl-imidazolium bromide) functionalized magnetic three-dimensional graphene oxide (Fe3O4@3D-GO@poly(ImC12+Br−)) was synthesized via a vacuum freezing-drying method and used as a magnetic solid phase extraction (MSPE) adsorbent for the efficient extraction of pyrethroid pesticides from tea samples. The prepared Fe3O4@3D-GO@poly(ImC12+Br−) was confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), vibrating sample magnetometer (VSM) and X-ray photoelectron spectrogram (XPS). Due to its large specific surface area and the ability to offer multiple intermolecular interactions, including π-π stacking, hydrophobic and hydrogen bond interactions, the prepared Fe3O4@3D-GO@poly(ImC12+Br−) showed high extraction efficiency for pyrethroids. The experimental parameters were optimized by a combination of single-factor method and Box-Behnken design to improve the extraction efficiency. Under the optimum conditions, coupled with high performance liquid chromatography (HPLC), a sensitive analytical method was developed for the determination of pyrethroids, and the proposed method showed wide linear ranges (1.00–100 μg L−1) with correlation coefficients (R) ranging from 0.9980 to 0.9994, low limits of detection (0.100 μg L−1) and good repeatability with intra-day relative standard deviations (RSDs) in the range of 2.90–5.53 % and inter-day RSDs in the range of 1.83–7.76 %. Moreover, the developed method was successfully applied to the determination of pyrethroids in tea samples and satisfactory recoveries ranging from 82.37 % to 114.34 % were obtained. The results showed that the developed Fe3O4@3D-GO@poly(ImC12+Br−) was an ideal, effective and selective material for the extraction and enrichment of pyrethroids from tea samples.

High throughput detection of veterinary drug residues in chicken and eggs

Co-extraction of multiple types of target substances is the key to achieve high throughput detection. In this work, PDA@MOF-808/PAN NFsM was prepared by co-modified polyacrylonitrile nanofiber membrane (PAN NFsM) with polydopamine (PDA) and metal-organic framework-808 (MOF-808), and its potential as a solid-phase extraction (SPE) adsorbent was investigated by using the most typical nine veterinary drug residues in eggs and chicken as model target substances. The results show that PDA@MOF-808/PAN NFsM could effectively co-extract all the target substances (adsorption efficiency ranged from 81.46 % to 96.78 %), and had good capability of sample matrix purification (matrix effect was lower than −15.26 %), so a new SPE method has been established. Combined with UPLC-MS/MS, the detection limits were 0.3 to 3.1 μg/kg, the recoveries were between 71.02 % and 106.48 %, and the relative standard deviations were lower than 12.03 %, indicating that the method has considerable good sensitivity, accuracy and precision.

COF-COOH@MIP as solid-phase extraction adsorbent for selective and sensitive detection of metamitron in environmental water

Metamitron (MET) is a selective herbicide widely used in agriculture but can persist in the environment and potentially contaminate water resources. This study reports the successful synthesis of a composite adsorbent, COF-COOH@MIP, specifically designed for MET preconcentration via solid-phase extraction (SPE) before high-performance liquid chromatography (HPLC) analysis. COF-COOH@MIP integrates the advantages of covalent organic frameworks (COFs) with their high surface area and stability and molecularly imprinted polymers (MIP) with their tailored recognition cavities. The adsorbent achieved a maximum adsorption capacity of 4.67 μg mg−1. The SPE column packed with COF-COOH@MIP demonstrated excellent reusability, with recovery rates of MET around 100 % after six consecutive cycles. The limit of detection (LOD) and limit of quantification (LOQ) of the established method were remarkably low, at 2.94 ng mL−1 and 9.80 ng mL−1, respectively. The linearity was credible within 0.03-400 μg mL−1 (R2 = 0.9999). The method’s applicability to real-world samples was validated by analyzing water from a farm, a ditch, and a river. This method offers a valuable tool for environmental monitoring programs to safeguard water quality from MET pollution.

Cyano-functionalized porous hyper-crosslinked cationic polymers for efficient preconcentration and detection of phenolic endocrine disruptors in fresh water and fish

Sensitively analyzing phenolic endocrine-disrupting chemicals (EDCs) in environmental substrates and aquatic organisms provides a significant challenge. Here, we developed a novel porous hyper-crosslinked ionic polymer bearing cyano groups (CN-HIP) as adsorbent for the highly efficient solid phase extraction (SPE) of phenolic EDCs in water and fish. The CN-HIP gave an excellent adsorption capability for targeted EDCs over a wide pH range, and the adsorption capacity was superior to that of several common commercial SPE adsorbents. The coexistence of electrostatic forces, hydrogen bond, and π-π interactions was confirmed as the main adsorption mechanism. A sensitive quantitative method was established by coupling CN-HIP based SPE method with high-performance liquid chromatography for the simultaneously determining trace bisphenol A, bisphenol F, bisphenol B and 4-tert-butylphenol in fresh water and fish. The method afforded lower detection limits (S/N = 3) (at 0.03–0.10 ng mL−1 for water and 0.8–4.0 ng g−1 for fish), high accuracy (the recovery of spiked sample at 88.0%–112 %) and high precision (the relative standard deviation < 8.5 %). This work provides a feasible method for detecting phenolic EDCs, and also opens a new perspective in developing functionalized cationic adsorbent.

Fabrication of sulfur-based functionalized activated carbon as solid phase extraction adsorbent for selective analysis of selenite in water

Based on the important feature of sulfur with excellent selectivity toward selenite in the presence of selenate, a simple and low-cost adsorbent of solid phase extraction known as sulfur loading activated carbon (SAC-6) was successfully prepared and applied for selenite (Se(IV)) analysis in water. Microstructure and morphological characteristics of SAC-6 had been identified by XRD, TEM, BET and FT-IR. In the static adsorption experiments, Se(IV) could be separated in a wide range of pH values (pH=3–11). The retention process of Se(IV) onto SAC-6 was characterized as spontaneous exothermic reaction. An obvious change of adsorption mechanism occurred in static and dynamic adsorption processes shown that the behaviors followed monolayer and hybrid adsorption. The theoretical maximum adsorption capacity of SAC-6 calculated by Langmuir-Freundlich was 13.48 mg/g. The microcolumn filled with SAC-6 was applied to extract Se(IV) in water solution. The detection limit of Se(IV) analytical procedure was confirmed as 0.27 μg/L within a linear range of 10–1000 μg/L. A good precision with relative standard deviation of 1.34 % (100 μg/L, n = 6) was achieved. The high adaptability and accuracy of SAC-6 microcolumn was validated by analyzing natural water samples and certified reference materials. Our work successfully excavated the application value of the sulfur selectivity, and also provided a new adsorbent for Se(IV) extraction and analysis.

Determination of Free Fatty Acids in Krill Oil during Storage Based on NH2-MMS.

In this study, amino-modified micro-mesoporous silica (NH2-MMS) with hierarchical pores was prepared by modifying micro-mesoporous silica ZSM-5 with 3-aminopropyltriethoxysilane and used as an adsorbent in solid-phase extraction to analyze free fatty acids (FFAs) in krill oil during storage for an initial time. The Brunner Emmet Teller adsorption experiment and Fourier transform infrared spectroscopy demonstrate that NH2-MMS, with a hierarchical pore structure, was successfully synthesized. The adsorption experiments, especially static adsorption, indicate that the absorption ability of the prepared NH2-MMS, with a hierarchical pore structure, toward FFAs was better than that of traditional amino-modified mesoporous silica (SBA-15) with a mesoporous structure at all temperature and concentrations. Fairly low limits of detection (0.06-0.15 μg g-1), acceptable recoveries (85.16-94.31%), and precision (0.08-5.26%) were attained under ideal circumstances. Moreover, NH2-MMS has the advantages of easy preparation and being environmentally friendly. As a result, this method offers an alternative to the current method for determining FFAs in different kinds of oil specimens.

Silver Core Coated with Molecularly Imprinted Polymer as Adsorbent in Pipet-Tip Solid Phase Extraction for Neonicotinoids Determination from Coconut Water.

In this work, we report an innovative adsorbent named Ag-MPS@MIP that has a core@shell structure, i.e., silver nanoparticles modified with 3-methacryloxypropyltrimethoxysilane as the core and molecularly imprinted polymer based on methacrylic acid as its shell. Thiamethoxam, imidacloprid, and acetamiprid were extracted from coconut water samples using Ag-MPS@MIP in pipet-tip solid phase, prior to high-performance liquid chromatography analysis. The separation was carried out on isocratic mode using a mobile phase consisting of C18 column (Phenomenex, 150 mm × 4.6 mm, 5 μm), ultrapure water acidified with 0.3% phosphoric acid:acetonitrile (78:22, v/v), flow rate at 1.0 mL min-1, injection volume of 10 μL, temperature of 25 °C, and wavelength at 260 nm. The adsorbent and precursor materials were properly characterized by different instrumental techniques. The main factors affecting the recovery of analytes from coconut water samples by pipet-tip solid phase were optimized, such as sample volume (250 μL), sample pH (pH = 5.0), ionic strength (1%, m/v), washing solvent (300 μL ultrapure water), volume and type of eluent (500 μL methanol), amount of adsorbent (15 mg), cycle of percolation-dispensing (1×), and reuse (5×). Thereby, the neonicotinoids presented extraction recoveries between 82.80 and 96.36%, enrichment factor of 5, linearity ranged from 15 to 4000 ng mL-1, correlation coefficient (r) > 0.99, limit of detection of 5 ng mL-1, satisfactory selectivity, stability, and proper precision (RSD%: 0.52-9.64%) and accuracy (RE%: -5.19-6.45%). The method was successfully applied to real samples of coconut water.