Aili Sun

Group-selective molecularly imprinted polymer solid-phase extraction for the simultaneous determination of six sulfonamides in aquaculture products.

Group-selective molecularly imprinted polymers (MIPs) made from sulfonamides (SAs) using functional monomer methacrylic acid (MAA) were synthesized. The derived molecularly imprinted solid-phase extraction (MISPE) cartridges were developed for the purification and enrichment of aquatic products. The optimum template molecule and the ratio of the functional monomer to the template for obtaining group selectivity to SAs were sulfadimethoxine (SDM) and 4:1, respectively. The MIPs were characterized by Brunauer-Emmett-Teller (BET), scatchard plot, and chromatography analysis, all of which demonstrate better chromatographic behavior and group-selectivity of MIPs for SAs compared with those of corresponding NIPs. The extraction conditions of MISPE for six SAs were optimized; the method precision and accuracy were satisfactory for the fish and shrimp samples at 0.05, 0.1, and 0.2 mg kg(-1) spiked levels. Recoveries ranging from 85.5% to 106.1% (RSD, 1.2-7.0%, n=3) were achieved. The limits of detection (S/N=3) and quantitation (S/N=10) in the shrimp and fish samples were achieved from 8.4 to 10.9 μg kg(-1) and from 22.4 to 27.7 μg kg(-1), respectively. Therefore, the obtained MIPs and MISPE can be employed for the enrichment and clean-up of SAs. This paper presents a new analytical method which enables the simultaneous determination and quantification of SAs in aquaculture products.

Group-selective enrichment and determination of pyrethroid insecticides in aquaculture seawater via molecularly imprinted solid phase extraction coupled with gas chromatography-electron capture detection

Two types of molecularly imprinted polymers (MIPs) for the simultaneous determination of six pyrethroid insecticides have been developed using deltamethrin (D-MIPs) and cypermethrin (C-MIPs) as template molecules. A comparison of the performance of D-MIPs, C-MIPs, and the corresponding non-imprinted polymers (NIPs) were conducted. Stronger group-selective interactions between the C-MIPs and the six pyrethroid insecticides were achieved. The MISPE method based on the C-MIPs displayed higher extraction recoveries (86.4-96.0%) with RSD values ranging from 2.4 to 7.8% for the six pyrethroid insecticides in aquaculture seawater. After the C-MIP cartridge procedure, the limits of detection and quantification for fenvalerate, deltamethrin, cypermethrin, cyfluthrin, and bifenthrin were in the 16.6-37.0 and 55.3-109.1 ng L⁻¹ ranges, respectively, and 0.68 and 2.26 μg L⁻¹ for phenothrin, respectively. The proposed MISPE method coupled with gas chromatography-electron capture detection was successfully used for the determination of the six pyrethroid insecticides in aquaculture seawater.

Characterisation and application of molecularly imprinted polymers for group-selective recognition of antibiotics in food samples

Group-selective molecularly imprinted polymers (MIPs) for amphenicol antibiotics, including chloramphenicol (CAP), thiamphenicol (TAP), florfenicol (FF), and florfenicol amine (FFA), were developed for the first time using TAP as the template molecule. The characteristics of the obtained MIPs were systematically evaluated by chromatographic methods and frontal analysis, demonstrating that the MIPs had excellent chromatographic behaviors, good selectivity, and high-binding capability. A molecularly imprinted solid-phase extraction (MISPE) procedure was developed based on the chromatography results. The MIPs exhibited better group selectivity for CAP, TAP, FF, and FFA than non-imprinted polymers (NIPs) under the optimized washing conditions of 10% acetonitrile in PBS buffer (25 mmol L(-1), pH = 5). Compared with conventional solid-phase extraction, significant recoveries ranging from 92.4% to 98.8% with lower relative standard deviation values in the range of 3.2-7.3% for both intraday- and interday-assays were obtained. The limits of detection (LODs) of MISPE for CAP, TAP, FF, and FFA in shrimp were found to be 0.016, 0.093, 0.102, and 0.029 μg kg(-1), respectively. The results acquired in this study contribute to the strategic development of MIPs and MISPE methods for the multi-residual recognition of antibiotics from complex matrices.

Highly permselective membrane surface modification by cold plasma-induced grafting polymerization of molecularly imprinted polymer for recognition of pyrethroid insecticides in fish.

Specific molecularly imprinted membranes (MIMs) for pyrethroid insecticides were developed and characterized for the first time in this study by cold plasma-induced grafting polymerization using methacrylic acid as a functional monomer and cypermethrin (CYP) as a template. The nonimprinted membranes (NIMs) were also synthesized using the same procedure without the template. Meanwhile, AFM, XPS, ATR-FTIR, contact angle, and permselectivity experiments were conducted to elucidate the imprinting and recognition properties of MIMs. Results demonstrated that MIMs exhibited excellent imprinting effect and high permselectivity. A molecularly imprinted-membrane-assisted solvent extraction (MI-MASE) method based on the MIMs was established. The operating conditions were optimized for group-selective extraction of the five pyrethroid insecticides. Compared with NIMs, higher extraction recoveries (83.8% to 100.6%) of the five pyrethroid insecticides by gas chromatography-electron capture detector (GC-ECD) were obtained using MIMs at three spiked levels in fish samples; the RSD values were lower than 8.3%. The limits of detection (LOD) and quantification (LOQ) defined as the concentrations at which the signal-to-noise (S/N) ratio is 3:1 and 10:1, respectively, were in the range of 0.26 to 0.42 μg/kg and 0.77 to 1.27 μg/kg, respectively. No matrix effect of the developed MI-MASE was observed by gas chromatography/tandem mass spectrometry (GC/MS/MS). These results demonstrated a highly selective, efficient, and environment-friendly MI-MASE technique for preconcentration and purification of pyrethroid insecticides from seafood, followed by GC-ECD and GC/MS/MS. The excellent applicability and potential of MI-MASE for routine monitoring of pyrethroid pesticides in food samples has also been confirmed.

Simultaneous analysis of polychlorinated biphenyls and organochlorine pesticides in seawater samples by membrane-assisted solvent extraction combined with gas chromatography-electron capture detector and gas chromatography-tandem mass spectrometry.

A highly efficient and environment-friendly membrane-assisted solvent extraction system combined with gas chromatography-electron capture detector was applied in the simultaneous determination of 17 polychlorinated biphenyls and organochlorine pesticides in seawater samples. Variables affecting extraction efficiency, including extraction solvent used, stirring rate, extraction time, and temperature, were optimized extensively. Under optimal extraction conditions, recoveries between 76.9% and 104.6% in seawater samples were achieved, and relative standard deviation values below 10% were obtained. The limit of detection (signal-to-noise ratio=3) and limit of quantification (signal-to-noise ratio=10) of 17 polychlorinated biphenyls and organochlorine pesticides in seawater ranged from 0.14ngL(-1) to 0.36ngL(-1) and 0.46ngL(-1) to 1.19ngL(-1), respectively. Matrix effects on extraction efficiency were evaluated by comparing with the results obtained using tap water. The extraction effect of developed membrane-assisted solvent extraction method was further demonstrated by gas chromatography-tandem mass spectrometry which can provide structural information of the analytes for more accurate identification, and results identical to those produced by gas chromatography-electron capture detector were obtained. These findings demonstrate the applicability of the developed membrane-assisted solvent extraction determination method for coupling to gas chromatography-electron capture detector or tandem mass spectrometry for determining polychlorinated biphenyls and organochlorine pesticides in seawater samples.

Determination of Chloramphenicol Residues in Foods by ELISA and LC-MS/MS Coupled with Molecularly Imprinted Solid Phase Extraction

The combination of molecularly imprinted solid-phase extraction (MISPE) with ELISA and LC-MS/MS was developed for the detection of chloramphenicol (CAP) in honey samples. Significant recoveries of 99.1 ± 7.1 and 98.8 ± 8.2% were obtained for intra- and inter-assay determination by ELISA determination, respectively. The limit of detection of CAP was 0.034 μg kg−1 and the limit of quantification was 0.046 μg kg−1. Determination and validation of CAP by using LC-MS/MS were performed following the same extraction and purification process as for the ELISA. The results demonstrated that the CAP samples purified by using MISPE were simultaneously applicable to analysis by ELISA and LC-MS/MS.

Development and application of a novel fluorescent nanosensor based on FeSe quantum dots embedded silica molecularly imprinted polymer for the rapid optosensing of cyfluthrin

A novel molecularly imprinted silica layer appended to FeSe quantum dots (MIP-FeSe-QDs) was fabricated and utilized as a recognition element to develop a selective and sensitive fluorescent nanosensor for cyfluthrin (CYF) determination. The MIP-FeSe-QDs were characterized by fluorescence spectrometry, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. Excellent selectivity and high sensitivity of MIP-FeSe-QDs to CYF molecules were observed based on the fluorescence quenching of FeSe-QDs. Under optimal conditions, a good linear relationship was found between fluorescence quenching effect and increased CYF concentration within 0.010-0.20mg/L, with a correlation coefficient of 0.9911. The practicality of the developed sensor method for CYF detection in fish and sediment samples was further validated. Good recoveries ranging from 88.0% to 113.9% with<6.8% relative standard deviations were obtained. The detection limits of CYF in sediment and fish samples were 1.3 and 1.0µg/kg, respectively. This study established a novel, rapid fluorescent nanosensor detection method based on MIP-QDs for successfully analyzing CYF in fish and sediment samples.

Development and evaluation of a DNA microarray assay for the simultaneous detection of nine harmful algal species in ship ballast and seaport waters

Rapid, high-throughput and reliable methods are urgently required to accurately detect and monitor harmful algae, which are responsible for algal blooms, such as red and green tides. In this study, we successfully developed a multiplex PCR-based DNA microarray method capable of detecting nine harmful algal species simultaneously, namely Alexandrium tamarense, Gyrodinium instriatum, Heterosigma akashiwo, Karenia mikimotoi, Prorocentrum donghaiense, Prorocentrum minimum, Ulva compressa, Ulva ohnoi and Ulva prolifera. This method achieved a limit of detection (LOD) of 0.5 ng of genomic DNA (orders of magnitude of the deci-nanogram range) in the tested algae cultures. Altogether, 230 field samples from ship ballast waters and seaport waters were used to evaluate the DNA microarray. The clinical sensitivity and specificity of the DNA microarray assay in detecting field samples were 96.4% and 90.9%, respectively, relative to conventional morphological methods. This indicated that this high-throughput, automatic, and specific method is well suited for the detection of algae in water samples.

Determination of lipophilic marine toxins in fresh and processed shellfish using modified QuEChERS and ultra-high-performance liquid chromatography-tandem mass spectrometry.

A simple QuEChERS method coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed to improve the extraction efficiency of lipophilic marine toxins (yessotoxins, dinophysistoxins, okadaic acid, azazspiracids, and spirolides) in fresh and processed shellfish products. The proposed method included freezing and dispersive solid-phase extraction with graphene oxide as the sorbent to clean complex matrices containing lipids (e.g., free fatty acids) and pigments. Quantification was performed using matrix-matched calibration curves. Recoveries were 85%-117.4% and the relative standard deviation for precision was less than 10% for marine toxins in fresh and processed shellfish products. The limits of detection (signal-to-noise = 3) and quantification (signal-to-noise = 10) were 0.10-1.47 and 0.32-4.92 μg/kg, respectively. The validated QuEChERS method, coupled with UPLC-MS/MS, was applied successfully to determine lipophilic marine toxins in fresh and processed shellfish samples.

An Electrochemiluminescence Sensor Based on Nafion/Magnetic Fe3O4 Nanocrystals Modified Electrode for the Determination of Bisphenol A in Environmental Water Samples.

The well-dispersive and superparamagnetic Fe3O4-nanocrystals (Fe3O4-NCs) which could significantly enhance the anodic electrochemiluminescence (ECL) behavior of luminol, were synthesized in this study. Compared to ZnS, ZnSe, CdS and CdTe nanoparticles, the strongest anodic ECL signals were obtained at +1.6 V on the Fe3O4-NCs coated glassy carbon electrode. The ECL spectra revealed that the strong ECL resonance energy transfer occurred between luminol and Fe3O4-NCs. Furthermore, under the optimized ECL experimental conditions, such as the amount of Fe3O4-NCs, the concentration of luminol and the pH of supporting electrolyte, BPA exhibited a stronger distinct ECL quenching effect than its structural analogs and a highly selective and sensitive ECL sensor for the determination of bisphenol A (BPA) was developed based on the Fe3O4-NCs. A good linear relationship was found between the ECL intensity and the increased BPA concentration within 0.01–5.0 mg/L, with a correlation coefficient of 0.9972. The detection limit was 0.66 × 10−3 mg/L. Good recoveries between 96.0% and 105.0% with a relative standard deviation of less than 4.8% were obtained in real water samples. The proposed ECL sensor can be successfully employed to BPA detection in environmental aqueous samples.