Magnetic nanoparticles solid phase extraction for determination of ochratoxin A in cereals using high-performance liquid chromatography with fluorescence detection

High-throughput extraction and automatic purification of alternariol from edible and medicinal herbs based on aptamer-functionalized magnetic nanoparticles

Mycotoxin contamination is widespread in plants and herbs, posing serious threats to the consumer and human health. Of them, alternariol (AOH) has attracted great attention as an "emerging" mycotoxin in medicinal herbs. However, a specific and high-throughput extraction method for AOH is currently lacking. Thus, developing an efficient pre-treatment technique for AOH detection is extremely vital. Here, a novel automated magnetic solid-phase extraction method was proposed for the highly efficient extraction of AOH. Combining the aptamer-functionalized magnetic nanoparticles (AMNPs) and the automatic purification instrument, AOH could be extracted in medicinal herbs in high throughput (20 samples) and a short time (30 min). The main parameters affecting extraction were optimized, and the method was finally carried out by incubation AMNPs with 3 mL of sample solution for 10 min, and then desorption in 75% methanol for liquid-phase detection. Under optimal conditions, good reproducibility, stability, and selectivity were realized with an adsorption capacity of 550.84 ng/mg. AOH extraction in three edible herbs showed good resistance to matrix interference with recovery rates from 86% to 111%. In combination with AMNPs and the automatic purification instrument, high-throughput and labor-free extraction of AOH in different complex matrices was achieved, which could be extended in other complex matrices.

Recent Advances in Mycotoxin Determination in Fish Feed Ingredients

Low-cost plant-based sources used in aquaculture diets are prone to the occurrence of animal feed contaminants, which may in certain conditions affect the quality and safety of aquafeeds. Mycotoxins, a toxic group of small organic molecules produced by fungi, comprise a frequently occurring plant-based feed contaminant in aquafeeds. Mycotoxin contamination can potentially cause significant mortality, reduced productivity, and higher disease susceptibility; thus, its timely detection is crucial to the aquaculture industry. The present review summarizes the methodological advances, developed mainly during the past decade, related to mycotoxin detection in aquafeed ingredients, namely analytical, chromatographic, and immunological methodologies, as well as the use of biosensors and spectroscopic methods which are becoming more prevalent. Rapid and accurate mycotoxin detection is and will continue to be crucial to the food industry, animal production, and the environment, resulting in further improvements and developments in mycotoxin detection techniques.

Application of Fe3O4@CNFs combined with deep eutectic solvent-based dual microextraction: a novel and green strategy for rapid determination of pesticides in edible oil samples

A novel, green, and effective strategy employing Fe₃O₄-modified carbon nanofibers (CNFs) combined with deep eutectic solvent (DES) is proposed as an extraction agent to extract five pesticides in edible oil samples via dual microextraction modes, followed by high-performance liquid chromatography for determination. The Fe₃O₄@CNFs nanomaterial and a sequence of hydrophilic DES were prepared at first and then characterized by multiple techniques. Subsequently, the extraction performance of DES and Fe₃O₄@CNFs-DES was compared and Fe₃O₄@CNFs-DES exhibited better extraction ability. After that, several influencing parameters such as the composition of DES, the amount of Fe₃O₄@CNFs-DES, the dispersion methods, and the extraction time were investigated and optimized. Eventually, Fe₃O₄@CNFs as the solid adsorbent combined with tetrabutylammonium chloride-lactic acid-based DES as the extraction solvent were selected to extract target pesticides from oil samples. The established method received good linearity in the range 25-1000 ng·g^-1. The limits of detection for all analytes were in the range 2.25-7.50 ng·mL^-1. Satisfactory recoveries of target pesticides were obtained (ranging from 82 to 117%) with a relative standard deviation of 0.26-9.46%. The proposed method has been successfully applied to the rapid detection of target pesticides in oil samples, demonstrating its great potential for quick screening and analysis.

An Immuno-Separated Assay for Ochratoxin Detection Coupled with a Nano-Affinity Cleaning-Up for LC-Confirmation

An immuno-separated assay for ochratoxin A detection coupled with a nano-affinity cleaning up for LC-confirmation was developed. Firstly, ochratoxin A was modified to quantum dot beads for immuno-fluorescent reporters. Secondly, Fe3O4 magnetic nanoparticles were conjugated with protein G for immuno-magnetic adsorbents. The immuno-separation of fluorescent reporters by magnetic adsorbents could be completed by ochratoxin A, so the fluorescent reporters released from the immune complex indicate a linear correlation with the concentration of ochratoxin A. Furthermore, the immuno-separated ochratoxin A can be eluted from magnetic adsorbent for LC-conformation. The optimized assay showed results as follows: the quantitative range of the immuno-separated assay was 0.03–100 ng mL−1 of ochratoxin A. The recoveries for spiked samples ranged from 78.2% to 91.4%, with the relative standard deviation (RSD) being 11.9%~15.3%. Statistical analysis indicated no significant difference between the HPLC-FLD results based on commercial affinity column and by nano-affinity cleaning up.

Solid-phase extraction techniques based on nanomaterials for mycotoxin analysis: An overview for food and agricultural products

Mycotoxin contamination is a globally concerned problem for food and agricultural products since it may directly or indirectly induce severe threats to human health. Sensitive and selective screening is an efficient strategy to prevent or reduce human and animal exposure to mycotoxins. However, enormous challenges exist in the determination of mycotoxins, arising from complex sample matrices, trace-level analytes, and the co-occurrence of diverse mycotoxins. Appropriate sample preparation is essential to isolate, purify, and enrich mycotoxins from complicated matrices, thus decreasing sample matrix effects and lowering detection limits. With the cross-disciplinary development, new solid-phase extraction strategies have been exploited and integrated with nanotechnology to meet the challenges of mycotoxin analysis. This review summarizes the advance and progress of solid-phase extraction techniques as the methodological solutions for mycotoxin analysis. Emphases are paid on nanomaterials fabricated as trapping media of SPE techniques, including carbonaceous nanoparticles, metal/metal oxide-based nanoparticles, and nanoporous materials. Advantages and limitations are discussed, along with the potential prospects. This article is protected by copyright. All rights reserved.

One-pot, facile synthesis and fast separation of a UiO-66 composite by a metalloporphyrin using nanomagnetic materials for oxidation of olefins and allylic alcohols

One-pot facile synthesis of a new composite based on the incorporation of a metalloporphyrin within the UiO-66 metal–organic framework is reported.

Development of extraction separation technology based on deep eutectic solvent and magnetic nanoparticles for determination of three sex hormones in milk

A rapid, reliable and eco-friendly method for the determination of three sex hormones in five kinds of milk was developed and validated by combining vortex-assisted liquid-liquid microextraction (VALLME) and magnetic solid-phase extraction (MSPE). Deep eutectic solvents (DESs) such as choline chloride/urea were considered as the extraction solvent in VALLME and multi-walled carbon nanotubes (MMWCNTs) were used as the adsorbent which could adsorb DESs on the surface. The optimum experimental conditions were as follows: amount of MMWCNTs for 10 mg, volume of acetone for 4 mL, no sodium chloride and extraction pH at 7. After the optimization of several main variables, satisfactory sensitivity levels were achieved as low as 1.0-1.3 ng mL^-1 and 2.5-4.5 ng mL^-1 for the limit of method detections and the limit of method quantitation, respectively. The recoveries of the three hormones in different milk samples were in the range of 80.1%-116.4%. Consequently, this method is suitable for monitoring the trace amount of sex hormones in milk matrices.

Deep eutectic solvent-based magnetic colloidal gel assisted magnetic solid-phase extraction: A simple and rapid method for the determination of sex hormones in cosmetic skin care toners

A simple rapid and efficient deep eutectic solvent-based magnetic colloidal gel (DES-MCG) assisted magnetic solid-phase extraction (MSPE) method followed by high performance liquid chromatography with a diode array detector (HPLC-DAD) was established for determination of four sex hormones (including ethinylestradiol, norgestrel, megestrol acetate and medroxyprogesterone acetate) in cosmetic skin care toners. The DES-MCG with the desirable advantages of high adsorbing ability was prepared by combining choline chloride/urea deep eutectic solvent and magnetic multiwalled carbon nanotubes (MMWCNTs). The synthesized DES-MCG was characterized using fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). The cosmetic skin care toners were concentrated by a rotary evaporator and the obtained solutions were further purified by DES-MCG assisted magnetic solid-phase extraction. Response surface methodology (RSM) was applied for efficient optimization of the main variables in the extraction procedure. Under the optimized conditions, method detection limits and method quantitation limits were in the range of 1.2-6.6 ng mL^-1 and 4.4-26.6 ng mL^-1, respectively. The recoveries of the four sex hormones in different cosmetic skin care toners ranged from 80.1% to 118.8% and the precisions were no more than 0.35%. The developed method was successfully applied for the determination of sex hormones in cosmetic skin care toners.

Label-Free Quantifications of Multiplexed Mycotoxins by G-Quadruplex Based on Photonic Barcodes

Multiplexed quantification of mycotoxins is of great significance in food safety. Here, novel photonic crystal (PhC) barcodes with G-quadruplex aptamer encapsulated for label-free multiplex mycotoxins quantification are developed. The probes are immobilized on PhC barcodes to form a molecular beacon (MB), which contains the sequences of mycotoxin aptamers and a G-quadruplex. In the presence of the target, the hairpin structure of MB would open and the region of the G-quadruplex is exposed, which subsequently combines with Thioflavin T (ThT) to produce fluorescence. The relative fluorescence intensity increased as the mycotoxins concentration increased in a linear range from 1.0 pg/mL to 100 ng/mL. Moreover, the multiplexed mycotoxins quantification could be achieved by tuning the structural color of the PhC barcodes. We demonstrate that this method with high accuracy and specificity for multiplexed detection of mycotoxins, with the sensitivity of the detection as low as 0.70 pg/mL. Our results show that G-quadruplex-encapsulated PhC barcodes offer a novel simple and label-free pathway toward the multiplex screen assay of mycotoxins for food safety.

Occurrence of mycotoxins in rice consumed by Iranians: a probabilistic assessment of risk to health

Risks based on cancer and non-cancer endpoints, to Iranians from exposure to several mycotoxins (aflatoxin B1, ochratoxin, deoxynivalenol and T-2 toxin) following consumption of rice were evaluated. Point estimates of hazard were made for each mycotoxin and a hazard index (HI) and probabilistic estimates were based on results of Monte Carlo Simulations (MCS). All known 17 peer-reviewed studies, published in databases included in Science Direct, PubMed, Scopus and Web of Science, as well as grey literature published in Google Scholar from 2008 to 2017 were considered. The 95^th and 50^th centiles of Hazard Index (HI) in Iranians due to ingestion of rice were estimated to be 2.5 and 0.5, respectively. The 95^th and 50^th centiles of people with positive surface antigens for hepatitis B (HBsAg+) risk characterisation for AFB₁ in Iranian consumers of rice were 81 and 79.1, respectively. The 95^th and 50^th centiles for risks of Iranians negative for the surface antigen of hepatitis B HBsAg (HBsAg-) were 4.4 and 2.6, respectively. Based on results of the MCS for risks to cancer effects, the 95^th and 50^th centiles of margins of exposure (MOE) were 233 and 231, respectively. Therefore, it is recommended to update agricultural approaches and storage methods and implement monitoring and regulations based on risks to health posed by consumption of rice by the Iranian population.

Remote Trice Light, Temperature, and pH-actuation of Switchable Magneto-Plasmonic Nanocarriers for Combinational Photothermal and Controlled/Targeted Chemotherapies

Three magneto-plasmonic nanohybrids were synthesized using Au- and Ag-coated Fe₃O₄ nanoparticles (NPs)-modified dual pH- and temperature-responsive triblock copolymer of poly (butyl methacrylate-co-acrylamide-co-methacrylic acid) to serve as drug carriers with potential of using in both photothermal and controlled/targeted chemotherapies. The internal superparamagnetic core gives the carriers targeted-delivery characteristics, and surface plasmon resonance-based noble metallic Au/Ag shells give them on-demand photothermal and photo-triggering release properties. To investigate the effect of coating method on the targeting property of synthesized carriers, Au NPs were attached to the magnetic core by 2 different direct/indirect procedures and the properties of the synthesized carriers including swelling ratio and thermal and optical sensitivity and switching were comprehensively investigated in 2 different buffer solutions with pH 5.5 and 7.4 at 37°C. Letrozole was used as a model anticancer drug and its loading and release properties were evaluated for the four nanocarriers. The cytotoxicity of drug-free and letrozole-loaded nanocarriers on normal L929 fibroblast and MDAMB 231 breast cancer cell lines was evaluated in absence/presence of laser radiation. The results revealed that the carriers have the potential of serving as switchable trimodal light/temperature/pH-triggered and targeted/controlled drug delivery platforms for chemophotothermal therapy.

Cetylpyridinium chloride functionalized silica-coated magnetite microspheres for the solid-phase extraction and pre-concentration of ochratoxin A from environmental water samples with high-performance liquid chromatographic analysis

A new method based on cetylpyridinium chloride coated ferroferric oxide/silica magnetic microspheres as an efficient solid-phase adsorbent was developed for the extraction and enrichment of ochratoxin A. The determination of ochratoxin A was obtained by high-performance liquid chromatography with fluorescence detection. In the presence of cetylpyridinium chloride, the adsorption capacity of ferroferric oxide/silica microspheres was 5.95 mg/g for ochratoxin A. The experimental parameters were optimized, including the amounts of ferroferric oxide/silica microspheres (20 mg) and cetylpyridinium chloride (0.18 mL, 0.5 mg/mL), pH value of media (9), ultrasonic time (5 min), elution solvent and volume [2(1 + 1) mL (washed twice, 1 mL each time) 1% acetic acid acetonitrile]. Under optimal experiment conditions, ochratoxin A had good linearity in the range of 2.5-250.0 ng/L in water samples with correlation coefficient of the calibration curve 0.9995. The limit of detection for ochratoxin A was 0.83 ng/L, and the recoveries were 89.8-96.8% with the relative standard deviation of 1.5-3.5% in environmental water samples. Furthermore, ferroferric oxide/silica microspheres show excellent reusability during extraction procedures for no less than six times.

Magnetic molecularly imprinted polymer nanoparticles for simultaneous extraction and determination of 6-mercaptopurine and its active metabolite thioguanine in human plasma

Cytotoxic drugs used in cancer chemotherapy require the continuous monitoring of their plasma concentration levels for dose adjustment purposes. Such condition necessitates the presence of a sensitive technique for accurate extraction and determination of these drugs together with their active metabolites. In this study a novel solid phase extraction technique using magnetic molecularly imprinted nanoparticles (MMI-SPE) is combined with liquid chromatography tandem mass spectrometry (LC-MS/MS) to extract and determine the anti-leukemic agent; 6-mercaptopurine (6-MP) and its active metabolite thioguanine (TG) in human plasma. The magnetic molecularly imprinted nanoparticles (Fe₃O₄@MIP NPs) were synthesized via precipitation polymerization technique and were characterized using different characterization methods A computational approach was adopted to help in the choice of the monomer used in the fabrication process. The Fe₃O₄@MIPs NPs possessed a highly improved imprinting efficiency, fast adsorption kinetics following 2nd order kinetics and good adsorption capacity of 1.0 mg/g. The presented MMI-SPE provided the optimum approach in comparison to other reported ones to achieve good extraction recovery and matrix effect of trace levels of 6-MP and TG from plasma. Chromatographic separation was carried out using a validated LC-MS/MS assay and recovery, matrix effect and process efficiency were evaluated. Recovery of 6-MP and TG was in the range of 85.94-103.03%, while, matrix effect showed a mean percentage recovery of 85.94-97.62% and process efficiency of 85.54-96.18%. The proposed extraction technique is simple, effective and can be applicable to the extraction and analysis of other pharmaceutical compounds in complex matrices for therapeutic drug monitoring applications.

Solid phase extraction as sample treatment for the determination of Ochratoxin A in foods: A review

Ochratoxin A (OTA) is a mycotoxin produced by two main types of fungi, Aspergillus and Penicillium species. OTA is a natural contaminant found in a large number of different matrices and is considered as a possible carcinogen for humans. Hence, low maximum permitted levels in foods have been established by competent authorities around the world, making essential the use of very sensitive analytical methods for OTA detection. Sample treatment is a crucial step of analytical methodology to get clean and concentrated extracts, and therefore low limits of quantification. Solid phase extraction (SPE) is a useful technique for rapid and selective sample preparation. This sample treatment enables the concentration and purification of analytes from the sample solution or extract by sorption on a solid sorbent. This review is focused on sample treatment procedures based on SPE prior to the determination of OTA in food matrices, published from 2010.

High-Throughput Low-Background G-Quadruplex Aptamer Chemiluminescence Assay for Ochratoxin A Using a Single Photonic Crystal Microsphere

We reported a novel hemin-G-quadruplex aptamer chemiluminescence assay platform for ochratoxin A (OTA) using the single silica photonic crystal microsphere (SPCM). The oligonucleotide A sequence containing aptamer sequences of hemin and OTA is immobilized on the surface of SPCM. The other oligonucleotide B sequence containing a partially complementary sequence with one part OTA aptamer and one part hemin aptamer is used as a blocking chain. The hybridization between chain A and chain B will be influenced by the presence or absence of OTA in the system, which will affect the bioactivity of DNAzyme. Thus, the chemiluminescence signal depends on the concentration of OTA in the samples. In the single particle assay platform, the signal/noise is remarkably enhanced, and the background signal can be ignored by separating hemin from the surface of SPCM. The limit of detection of the new method reaches to the pg/mL scale, and the linear detection range is 4 orders of magnitude for OTA. The new assay platform can provide a sensitive, cost-efficient, simple, and high-throughput screening for OTA.

A Rapid Magnetic Solid Phase Extraction Method Followed by Liquid Chromatography-Tandem Mass Spectrometry Analysis for the Determination of Mycotoxins in Cereals

Mycotoxins can contaminate various food commodities, including cereals. Moreover, mycotoxins of different classes can co-contaminate food, increasing human health risk. Several analytical methods have been published in the literature dealing with mycotoxins determination in cereals. Nevertheless, in the present work, the aim was to propose an easy and effective system for the extraction of six of the main mycotoxins from corn meal and durum wheat flour, i.e., the main four aflatoxins, ochratoxin A, and the mycoestrogen zearalenone. The developed method exploited magnetic solid phase extraction (SPE), a technique that is attracting an increasing interest as an alternative to classical SPE. Therefore, the use of magnetic graphitized carbon black as a suitable extracting material was tested. The same magnetic material proved to be effective in the extraction of mycoestrogens from milk, but has never been applied to complex matrices as cereals. Ultra high–performance liquid chromatography tandem mass spectrometry was used for detection. Recoveries were >60% in both cereals, even if the matrix effects were not negligible. The limits of quantification of the method results were comparable to those obtained by other two magnetic SPE-based methods applied to cereals, which were limited to one or two mycotoxins, whereas in this work the investigated mycotoxins belonged to three different chemical classes.

Facile synthesis of Fe3O4/MIL-101 nanocomposite as an efficient heterogeneous catalyst for degradation of pollutants in Fenton-like system

An active Fe₃O₄/MIL-101 hybrid material was prepared via a simple in situ solvothermal method and characterized as a heterogeneous Fenton-like catalyst for Rhodamine B (RhB) degradation.

Preparation of magnetic metal organic framework composites for the extraction of neonicotinoid insecticides from environmental water samples

The process of fabrication of Fe₃O₄/MOF-199 composites and adsorbing pesticides.

Surfactant-enhanced spectrofluorimetric determination of total aflatoxins from wheat samples after magnetic solid-phase extraction using modified Fe₃O₄ nanoparticles

The extraction and preconcentration of total aflatoxins (including aflatoxin B1, B2, G1, and G2) using magnetic nanoparticles based solid phase extraction (MSPE) followed by surfactant-enhanced spectrofluorimetric detection was proposed. Ethylene glycol bis-mercaptoacetate modified silica coated Fe3O4 nanoparticles as an efficient antibody-free adsorbent was successfully applied to extract aflatoxins from wheat samples. High surface area and strong magnetization properties of magnetic nanoparticles were utilized to achieve high enrichment factor (97), and satisfactory recoveries (92-105%) using only 100mg of the adsorbent. Furthermore, the fast separation time (less than 10 min) avoids many time-consuming cartridge loading or column-passing procedures accompany with the conventional SPE. In determination step, signal enhancement was performed by formation of Triton X-100 micelles around the analytes in 15% (v/v) acetonitrile-water which dramatically increase the sensitivity of the method. Main factors affecting the extraction efficiency and signal enhancement of the analytes including pH of sample solution, desorption conditions, extraction time, sample volume, adsorbent amount, surfactant concentration and volume and time of micelle formation were evaluated and optimized. Under the optimum conditions, wide linear range of 0.1-50 ng mL(-1) with low detection limit of 0.03 ng mL(-1) were obtained. The developed method was successfully applied to the extraction and preconcentration of aflatoxins in three commercially available wheat samples and the results were compared with the official AOAC method.

Synthesis of magnetic molecularly imprinted polymers by reversible addition fragmentation chain transfer strategy and its application in the Sudan dyes residue analysis

Magnetic molecularly imprinted polymers (MMIPs) have become a hotspot owing to the dual functions of target recognition and magnetic separation. In this study, the MMIPs were obtained by the surface-initiated reversible addition fragmentation chain transfer (RAFT) polymerization using Sudan I as the template. The resultant MMIPs were characterized by transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometer, and X-ray diffraction. Benefiting from the controlled/living property of the RAFT strategy, the uniform MIP layer was successfully grafted on the surface of RAFT agent-modified Fe3O4@SiO2 nanoparticles, favoring the fast mass transfer and rapid binding kinetics. The developed MMIPs were used as the solid-phase extraction sorbents to selectively extract four Sudan dyes (Sudan I, II, III, and IV) from chili powder samples. The recoveries of the spiked samples in chili powder samples ranged from 74.1 to 93.3% with RSD lower than 6.4% and the relative standard uncertainty lower than 0.029. This work provided a good platform for the extraction and removal of Sudan dyes in complicated matrixes and demonstrated a bright future for the application of the well-constructed MMIPs in the field of solid-phase extraction.

Metal-organic framework UiO-66 modified magnetite@silica core-shell magnetic microspheres for magnetic solid-phase extraction of domoic acid from shellfish samples

Fe3O4@SiO2@UiO-66 core-shell magnetic microspheres were synthesized and characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectrometry, vibrating sample magnetometry, nitrogen adsorption porosimetry and zeta potential analyzer. The synthesized Fe3O4@SiO2@UiO-66 microspheres were first used for magnetic solid-phase extraction (MSPE) of domoic acid (DA) in shellfish samples. Combined with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), a fast, simple and sensitive method for the determination of DA was established successfully. Under the optimized conditions, the developed method showed short analysis time, good linearity (r(2) = 0.9990), low limit of detection (1.45 pg mL(-1); S/N = 3:1), low limit of quantification (4.82 pg mL(-1); S/N = 10:1), and good extraction repeatability (RSD ≤ 5.0%; n = 5). Real shellfish samples were processed using the developed method, and trace level of DA was detected. The results demonstrate that Fe3O4@SiO2@UiO-66 core-shell magnetic microspheres are the promising sorbents for rapid and efficient extraction of polar analytes from complex biological samples.

Development of a nanobody-alkaline phosphatase fusion protein and its application in a highly sensitive direct competitive fluorescence enzyme immunoassay for detection of ochratoxin A in cereal

A rapid and sensitive direct competitive fluorescence enzyme immunoassay (dc-FEIA) for ochratoxin A (OTA) based on a nanobody (Nb)-alkaline phosphatase (AP) fusion protein was developed. The VHH (variable domain of heavy chain antibody) gene of Nb28 was subcloned into the expression vector pecan45 containing the AP double-mutant gene. The Nb28-AP construct was transformed into Escherichia coli BL21(DE3)plysS, and soluble expression in bacteria was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot. Both the Nb properties and AP enzymatic activity were validated by colorimetric and fluorometric analysis. The 50% inhibitory concentration and the detection limit of the dc-FEIA were 0.13 and 0.04 ng/mL, respectively, with a linear range of 0.06-0.43 ng/mL. This assay was compared with LC-MS/MS, and the results indicated the reliability of Nb-AP fusion protein-based dc-FEIA for monitoring OTA contamination in cereal.

Magnetic Solid Phase Extraction Applied to Food Analysis

Magnetic solid phase extraction has been used as pretreatment technique for the analysis of several compounds because of its advantages when it is compared with classic methods. This methodology is based on the use of magnetic solids as adsorbents for preconcentration of different analytes from complex matrices. Magnetic solid phase extraction minimizes the use of additional steps such as precipitation, centrifugation, and filtration which decreases the manipulation of the sample. In this review, we describe the main procedures used for synthesis, characterization, and application of this pretreatment technique which were applied in food analysis.

Ionic-liquid-micelle-functionalized mesoporous Fe3O4 microspheres for ultraperformance liquid chromatography determination of anthraquinones in dietary supplements

A magnetic solid-phase extraction method using ionic liquid (IL)-micelle-functionalized mesoporous Fe3O4 microspheres (MFMs) was proposed for the preconcentration of anthraquinones in dietary supplements. The analytes were then determined by ultraperformance liquid chromatography combined with an ultraviolet detector. The extraction parameters, such as the choice of ILs, the concentrations of ILs and MFMs, the pH of diluent, and the concentration of acetic acid in the eluent, were presented. Under the optimized conditions, the limits of detection and limits of quantitation were 0.4-2.8 ng mL(-1) and 1.4-9.4 ng mL(-1), respectively. The accuracy of the proposed method was investigated by recovery in herb and granules of Radix et Rhizoma Rhei, yielding values between 89.25% and 96.48%. The use of the proposed method in the sample pretreatment of complex dietary supplements is feasible due to the high surface area and excellent adsorption capacity of MFMs after modification with IL.

VHH phage-based competitive real-time immuno-polymerase chain reaction for ultrasensitive detection of ochratoxin A in cereal

Phage display-mediated immuno-polymerase chain reaction (PD-IPCR) is an ultrasensitive detection technology that combines the advantages of immuno-PCR and phage display. The phage particle, which displayed antibody fragments including single-chain fragment variable (scFv), variable domain of heavy-chain antibodies (VHH), and antigen-binding fragment (Fab) on the surface can be directly used in IPCR, supplying both the detection antibody and deoxyribonucleic acid (DNA) template. In this work, we used ochratoxin A (OTA) as a model system to study the capacity of PD-IPCR in the detection of toxic small molecular weight compounds, especially mycotoxins. An alpaca-derived VHH library was constructed and subjected to four cycles of panning. In total, 16 clones with four unique sequences were selected by competitive binding with OTA. The clone VHH-28 resulted in the lowest 50% inhibitory concentration of 0.31 ng/mL in the phage enzyme-linked immunosorbent assay (ELISA) and was selected to develop the VHH phage-based real-time immuno-PCR (RT-IPCR). The detection limit of the VHH phage-based RT-IPCR was 3.7 pg/L, with a linear range of 0.01-1000 pg/mL. This method was compared with conventional ELISA, and validation results indicated the reliability of VHH phage-based RT-IPCR in the detection of OTA in cereal samples. This study provides a new idea for the ultrasensitive detection of mycotoxins and other toxic small molecular weight compounds.

Magnetically assisted solid phase extraction using Fe3O4 nanoparticles combined with enhanced spectrofluorimetric detection for aflatoxin M1 determination in milk samples

A novel, facile and inexpensive solid phase extraction (SPE) method using ethylene glycol bis-mercaptoacetate modified 3-(trimethoxysilyl)-1-propanethiol grafted Fe(3)O(4) nanoparticles coupled with spectrofluorimetric detection was proposed for determination of aflatoxin M1 (AFM1) in liquid milk samples. The method uses the advantage fluorescence enhancement by β-cyclodexterin complexation of AFM1 in 12% (v/v) acetonitrile-water and the remarkable properties of Fe(3)O(4) nanoparticles namely high surface area and strong magnetization were utilized to achieve high enrichment factor (57) and satisfactory extraction recoveries (91-102%) using only 100 mg of magnetic adsorbent. Furthermore, fast separation time of about 15 min avoids many time-consuming column-passing procedures of conventional SPE. The main factors affecting extraction efficiency including pH value, desorption conditions, extraction/desorption time, sample volume, and adsorbent amount were evaluated and optimized. Under the optimal conditions, a wide linear range of 0.04-8 ng mL(-1) with a low detection limit of 0.015 ng mL(-1) was obtained. The developed method was applied for extraction and preconcentration of AFM1 in three commercially available milk samples and the results were compared with the official AOAC method.