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

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

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

Tuning the planarity of molecularly imprinted covalent organic frameworks for selective extraction of ochratoxin A in alcohol samples

Here, we report a monomer planarity modulation strategy for room-temperature constructing molecularly imprinted-covalent organic frameworks (MI-COFs) for selective extraction of ochratoxin A (OTA). 2,4,6-triformylphloroglucinol (Tp) was used as basic building block, while three amino monomers with different planarity were employed as modulators to explore the effect of planarity on the selectivity of MI-COFs. The MI-TpTapa constructed from Tp and the lowest planarity of monomer Tapa gave the highest selectivity for OTA, and was further used as the adsorbent for dispersed-solid phase extraction (DSPE) of OTA in alcohol samples. Coupling MI-TpTapa based DSPE with high-performance liquid chromatography allowed the matrix-effect free determination of OTA in alcohol samples with the limit of detection of 0.023 μg kg-1 and the recoveries of 91.4-97.6%. The relative standard deviation (RSD, n = 6) of intra and inter day was <3.2%. This work provides a new way to construct MI-COFs for selective extraction of hazardous targets.

Innovative approaches for mycotoxin detection in various food categories

Mycotoxins (MTs), produced by filamentous fungi, represent a severe hazard to the health of humans and food safety, affecting the quality of various agricultural products. They can contaminate a wide range of foods, during any processing phase before or after harvest. Animals and humans who consume MTs-contaminated food or feed may experience acute or chronic poisoning, which may result in serious pathological consequences. Accordingly, developing rapid, easy, and accurate methods of MTs detection in food becomes highly urgent and critical as a quality control and to guarantee food safety and lower health hazards. In this review, we highlighted and discussed innovative approaches like biosensors, fluorescent polarization, capillary electrophoresis, infrared spectroscopy, and electronic noses for MT identification pointing out current challenges and future directions. The limitations, current challenges, and future directions of conventional detection methods versus innovative methods have also been highlighted and discussed.

Application of Sorbent-Based Extraction Techniques in Food Analysis

This review presents an outline of the application of the most popular sorbent-based methods in food analysis. Solid-phase extraction (SPE) is discussed based on the analyses of lipids, mycotoxins, pesticide residues, processing contaminants and flavor compounds, whereas solid-phase microextraction (SPME) is discussed having volatile and flavor compounds but also processing contaminants in mind. Apart from these two most popular methods, other techniques, such as stir bar sorptive extraction (SBSE), molecularly imprinted polymers (MIPs), high-capacity sorbent extraction (HCSE), and needle-trap devices (NTD), are outlined. Additionally, novel forms of sorbent-based extraction methods such as thin-film solid-phase microextraction (TF-SPME) are presented. The utility and challenges related to these techniques are discussed in this review. Finally, the directions and need for future studies are addressed.

Simultaneous determination of multiple mycotoxins in corn and wheat by high efficiency extraction and purification based on polydopamine and ionic liquid bifunctional nanofiber mat

Due to the universality and harmfulness of mycotoxin co-contamination in cereals, it is of great significance to simultaneously monitor various mycotoxins co-polluted to ensure food safety and public health. In this work, a nanofiber mat modified by polydopamine and ionic liquid (PDA-IL-NFsM) was prepared and utilized as a solid-phase extraction (SPE) adsorbent for the simultaneous quantitative detection of multiple mycotoxins in corn and wheat. The PDA-IL-NFsM can form multiple retention mechanisms with the targets through hydrogen bond, π-π interaction, electrostatic or hydrophobic interaction, it shows favorable simultaneous adsorption performance (adsorption efficiency mostly higher than 88.27%) for fifteen mycotoxins in seven classes. Moreover, it can significantly reduce the matrix effect (lower than -13.69%), showing a good purification effect on the sample matrix. Based on the superior performance of PDA-IL-NFsM, a simple sample preparation method was established. The sample extract is simply diluted with water for SPE, and the eluent can be directly collected for ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) analysis. The detection limit can reach 0.04-4.21 μg kg^-1, the recovery was 80.09%-113.01%, and the relative standard deviations of intra-day and inter-day precision were 2.80%-14.81% and 0.68%-13.80% respectively. The results show that the proposed method has good sensitivity, accuracy and precision, and has practical application potential.

Development of a Novel Magnetic-Bead-Based Automated Strategy for Efficient and Low-Cost Sample Preparation for Ochratoxin A Detection Using Mycotoxin–Albumin Interaction

The mycotoxin ochratoxin A (OTA) is toxic to humans and frequently contaminates wine and beer. Antibodies are essential recognition probes for the detection of OTA. However, they have several drawbacks, such as high costs and difficulty in preparation. In this study, a novel magnetic-bead-based automated strategy for efficient and low-cost OTA sample preparation was developed. Human serum albumin, which is an economical and stable receptor based on the mycotoxin–albumin interaction, was adapted and validated to replace conventional antibodies to capture OTA in the sample. Ultra-performance liquid chromatography–fluorescence detection was used in combination with this preparation method for efficient detection. The effects of different conditions on this method were investigated. The recovery of OTA samples spiked at three different concentrations ranged from 91.2% to 102.1%, and the relative standard deviations (RSDs) were 1.2%–8.2% in wine and beer. For red wine and beer samples, the LODs were 0.37 and 0.15 µg/L, respectively. This reliable method overcomes the drawbacks of conventional methods and offers significant application prospects.

Ultra-sensitive determination of Ochratoxin A in coffee and tea samples using a novel semi-automated in-syringe based coagulant-assisted fast mycotoxin extraction (FaMEx) technique coupled with UHPLC-MS/MS

In this study, we demonstrated a novel semi-automated in-syringe-based coagulant-assisted liquid-liquid microextraction (IS-CGA-LLME) as fast mycotoxin extraction (FaMEx) technique coupled with ultra-high-performance liquid chromatography connected with a tandem-mass spectrometer (UHPLC-MS/MS) for the quantification of mycotoxin (Ochratoxin A, OT-A) in coffee and tea samples. IS-CGA-LLME is a three-step extraction process that includes extraction of OT-A from sample matrix using low-volume solvent extraction, then the extractant was cleaned-up using a coagulation process, and finally, the decolorized/matrix removed sample solution was processed for LLME for target analyte's pre-concentration. The final extractant was analyzed using UHPLC-MS/MS for OT-A quantification. Under the optimized experimental conditions, highly sensitive detection and quantification limits were obtained at 0.001 and 0.003 ng g^-1 for OT-A with excellent extraction recovery (93-111%) and precision <10%. These results proved that the developed method is a simple, highly sensitive, semi-automated, low-matrix effect and efficient procedure for the determination of mycotoxins in food samples.

Multi-mycotoxin detection and human exposure risk assessment in medicinal foods

Mycotoxin contamination in medicinal foods has attracted increasing global attention. In this study, a simple and sensitive ultrasonication assisted one-step extraction based ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method was developed for simultaneous detection of multi-mycotoxins in five kinds of medicinal foods rich in starch. Under optimal conditions, the developed technique displayed excellent analytical performances. Limits of detection and quantitation for the six mycotoxins were 0.04-0.25 ng/mL and 0.10-0.67 ng/mL, respectively. Average recoveries at three fortified levels ranged from 75.33 % to 118.0 %. Real-world application in 103 batches of medicinal foods displayed that 58 samples were positive with one or more mycotoxins at an occurrence rate of 56.31 % (58/103). Coix seed gave the highest positive rate of 96.15 %, followed by Lily (90 %), Chinese yam (50 %), Lotus seed (34.04 %) and Malt (30 %). Zearalenone had the highest positive rate of 28.16 % with contents in 5 Coix seeds exceeding the maximum residue limit (MRL), followed by aflatoxin B₁ of 27.18 % (28/103) with contents in 7 Coix seed and 10 Lotus seeds over its MRL, and ochratoxin A (OTA) of 11.65 % with contents in 1 Lotus seed and 5 Lily samples greater than its MRL. Exposure risk assessment indicated that Coix seed and Lotus seeds that were susceptible to aflatoxins posed great threats to human health. Long-term consumption of Lily that was easily contaminated with OTA were also harmful. This work provides a robust platform for multi-mycotoxin monitoring in medicinal foods to protect the consumers from potential health risks.

Fast and Accurate Determination of Minute Ochratoxin A Levels in Cereal Flours and Wine with the Label-Free White Light Reflectance Spectroscopy Biosensing Platform

Ochratoxin A (OTA) is one of the most toxic naturally encountered contaminants and is found in a variety of foods and beverages, including cereals and wine. Driven by the strict regulations regarding the maximum allowable OTA concentration in foodstuff and the necessity for on-site determination, the development of fast and sensitive methods for the OTA determination in cereal flours and wine samples, based on white light reflectance spectroscopy, is presented. The method relied on appropriately engineered silicon chips, on top of which an OTA-protein conjugate was immobilized. A polyclonal antibody against OTA was then employed to detect the analyte in the framework of a competitive immunoassay; followed by the subsequent addition of a biotinylated secondary antibody and streptavidin for signal enhancement. A small size instrument performed all assay steps automatically and the bioreactions were monitored in real time as the software converted the spectral shifts into effective biomolecular adlayer thickness increase. The assay developed had a detection limit of 0.03 ng/mL and a working range up to 200 ng/mL. The assay lasted 25 min (less than 1h, including calibrators/antibody pre-incubation) and was accomplished following a simple sample preparation protocol. The method was applied to corn and wheat flour samples and white and red wines with recovery values ranging from 87.2 to 111%. The simplicity of the overall assay protocol and convenient instrumentation demonstrates the potential of the immunosensor developed for OTA detection at the point of need.

Research Advances in the Analysis of Estrogenic Endocrine Disrupting Compounds in Milk and Dairy Products

Milk and dairy products are sources of exposure to estrogenic endocrine disrupting compounds (e-EDCs). Estrogenic disruptors can accumulate in organisms through the food chain and may negatively affect ecosystems and organisms even at low concentrations. Therefore, the analysis of e-EDCs in dairy products is of practical significance. Continuous efforts have been made to establish effective methods to detect e-EDCs, using convenient sample pretreatments and simple steps. This review aims to summarize the recently reported pretreatment methods for estrogenic disruptors, such as solid-phase extraction (SPE) and liquid phase microextraction (LPME), determination methods including gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), Raman spectroscopy, and biosensors, to provide a reliable theoretical basis and operational method for e-EDC analysis in the future.

Rapid screening of neuraminidase inhibitors with the benzoic acid skeleton from Paeonia suffruticosa Andrews by solid-phase extraction with an enzyme activity switch combined with mass spectrometry analysis

It is meaningful for drug discovery to discover lead compounds with specific skeletons from medicinal herbs. Screening bioactive compounds with specific skeletons by a simple and rapid strategy is still a challenging task. Solid-phase extraction (SPE) is a simple and time-saving technique in the laboratory and is often used in the concentration of natural products. It is attractive to apply the SPE in the screening of bioactive compounds with specific skeletons. To achieve this goal, SPE with an enzyme activity (EA) switch combined with mass spectrometry analysis was first proposed. The screening of benzoic acid-derived neuraminidase (NA) inhibitors from the root cortex of Paeonia suffruticosa Andrews (CPSA) was used as an example. The NA and crude extract of CPSA were incubated to form a sample solution. Subsequently, the sample was separated, detected, and collected by the SPE with an EA switch. When the detected values reduced significantly, the EA switch was triggered, and the collection was stopped. The collected eluents were treated for LC-MS/MS analysis. Finally, combining diagnostic ions and mass spectrometry data, two benzoic acid NA inhibitors were successfully screened from CPSA. In this study, the separation, detection, and collection were performed on one instrument system. Compared with the traditional isolation strategy, this strategy with the simpler operation and higher experimental efficiency could be an effective tool for the rapid screening of lead compounds with specific skeletons.

Nanomaterial-based aptamer biosensors for ochratoxin A detection: a review

Ochratoxin A (OTA) is a widely distributed mycotoxin that often contaminates food, grains and animal feed. It poses a serious threat to human health because of its high toxicity and persistence. Therefore, the development of an inexpensive, highly sensitive, accurate and rapid method for OTA detection is imperative. In recent years, various nanomaterials used in the establishment of aptasensors have attracted great attention due to their large surface-to-volume ratio, good stability and facile preparation. This review summarizes the development of nanomaterial-based aptasensors for OTA determination and sample treatment over the past 5 years. The nanomaterials used in OTA aptasensors include metal, carbon, luminescent, magnetic and other nanomaterials. Finally, the limitations and future challenges in the development of nanomaterial-based OTA aptasensors are reviewed and discussed.

The Existing Methods and Novel Approaches in Mycotoxins' Detection

Mycotoxins represent a wide range of secondary, naturally occurring and practically unavoidable fungal metabolites. They contaminate various agricultural commodities like cereals, maize, peanuts, fruits, and feed at any stage in pre- or post-harvest conditions. Consumption of mycotoxin-contaminated food and feed can cause acute or chronic toxicity in human and animals. The risk that is posed to public health have prompted the need to develop methods of analysis and detection of mycotoxins in food products. Mycotoxins wide range of structural diversity, high chemical stability, and low concentrations in tested samples require robust, effective, and comprehensible detection methods. This review summarizes current methods, such as chromatographic and immunochemical techniques, as well as novel, alternative approaches like biosensors, electronic noses, or molecularly imprinted polymers that have been successfully applied in detection and identification of various mycotoxins in food commodities. In order to highlight the significance of sampling and sample treatment in the analytical process, these steps have been comprehensively described.

Recent progress in determination of ochratoxin a in foods by chromatographic and mass spectrometry methods

Ochratoxin A is a highly toxic mycotoxin and has posed great threat to human health. Due to its serious toxicity and wide contamination, great efforts have been made to develop reliable determination methods. In this review, analytical methods are comprehensively summarized in terms of sample preparation strategy and instrumental analysis. Detailed method is described according to the food commodities in the order of cereal, wine, coffee, beer, cocoa, dried fruit and spice. This review mainly focuses on the recent advances, especially reported in the last decade. At last, challenges and perspectives are also discussed to achieve better advancement and promote practical application in this field.

A label-free, direct solid-phase fluorimetric analysis of ochratoxin A in agricultural products with monoclonal antibody-immobilized monolith

We established a method for directly measuring mycotoxin ochratoxin A (OTA) in foods by solid-phase fluorescence of monolith-immobilized antibodies. The antibody was introduced onto only one side of an 8 mm-diameter, 3 mm-thick monolith via covalently immobilized protein G. 4 μg (2.7 × 10^-11 mol) of antibody was immobilized per one monolith. A maximum of 10 μg (2.4 × 10^-11 mol) OTA adsorbed to the activated side of each monolith. The amount of OTA adsorbed and the fluorescence intensity showed good linearity in the range of 0.5-3 ng OTA. Loading the sample solution onto the non-antibody side on the monolith blocked the hydrophobic fluorescent matrices from reaching the immobilized surface of the antibody. The proposed method was able to detect 1 ng OTA/g in solid samples with complex matrices. Mean recoveries obtained at spiked concentration of 3 ng g^-1 OTA/g were 78-90% with relative standard deviations of <7.9%.

Determination of ochratoxin A in coffee and tea samples by coupling second-order multivariate calibration and fluorescence spectroscopy

A new method to quantify the mycotoxin ochratoxin A (OTA) in coffee and tea samples is proposed based on second-order multivariate calibration and excitation-emission fluorescence matrix (EEFM) data. Experimental conditions were optimized by studying the effect of pH and various organized media on the fluorescence signal of OTA. For each analysed matrix (coffee grains and tea leaves), several sample pretreatments and calibration methods (external or standard addition) and data processing by chemometric models (e.g., parallel factor analysis/PARAFAC and multivariate curve resolution-alternating least squares/MCR-ALS) were evaluated and discussed. The MCR-ALS algorithm provided an adequate fit to the data for both samples, while PARAFAC was satisfactory only for the tea samples. Regarding the figures of merit, the limits of detection were in the range of 0.2-0.3 ng mL^-1; furthermore, low relative prediction errors, between 2% and 4%, were achieved in both the fortified and real samples. Accordingly, the proposed methodology was applied to analyse fortified roasted and green coffee and real tea leaf samples. Satisfactory recoveries were achieved (ranging from 92 to 110%), and the obtained concentrations were in agreement with the values obtained by the reference method (based on high-performance liquid chromatography with fluorescence detection/HPLC-FLD). In addition, all samples contained OTA levels lower than the maximum permissible levels. Finally, the proposed strategy allows the use of green analytical chemistry principles; for instance, the use of organic solvents and the generation of waste products were significantly lower than for similar analytical methods reported in the literature.

Pre-Concentration and Analysis of Mycotoxins in Food Samples by Capillary Electrophoresis

Mycotoxins are considered one of the most dangerous agricultural and food contaminants. They are toxic and the development of rapid and sensitive analytical methods to detect and quantify them is a very important issue in the context of food safety and animal/human health. The need to detect mycotoxins at trace levels and to simultaneously analyze many different mycotoxin types became mandatory to protect public health. In fact, European Commission regulations specified both their limits in foodstuffs and official sample preparation protocols in addition to analytical methods to verify their presence. Capillary Electrophoresis (CE) includes different separation modes, allowing many versatile applications in food analysis and safety. In the context of mycotoxins, recent advances to improve CE sensitivity, particularly pre-concentration techniques or miniaturized systems, deserve remarkable attention, as they provide an interesting approach in the analysis of such contaminants in complex food matrices. This review summarizes the applications of CE combined with different pre-concentration approaches, which have been proposed in the literature (mainly) in the last ten years. A section is also dedicated to recent microchip–CE devices since they represent the most promising CE mode for this application.

Evaluation of Two Fully Automated Setups for Mycotoxin Analysis Based on Online Extraction-Liquid Chromatography-Tandem Mass Spectrometry

Mycotoxins are secondary metabolites of fungi species widely known for their potentially toxic effects on human health. Considering their frequent presence in crops and their processed food, monitoring them on food-based matrices is now an important topic. Within such a context, the sample preparation step is usually mandatory before the chromatographic analysis, due to the complexity of matrices such as nuts, cereals, beverages, and others. For these reasons, we herein present the evaluation of two greener setups, based on the automation and miniaturization of the sample preparation step for mycotoxin analysis in different beverages. Firstly, we describe an analytical method based on a multidimensional assembly, coupling a lab-made microextraction column (508 µm i.d. × 100 mm) to a UPLC–MS/MS for the analysis of ochratoxin A in beverages. This configuration used a synthesized sorbent phase containing C18-functionalized graphene–silica particles, which exhibited excellent extraction performance, as well as being reusable and cheaper than commercially available extractive phases. Sequentially, a second setup, based on a multidimensional capillary LC coupled to MS/MS, was assessed for the same purpose. In this case, a graphene oxide-based capillary extraction column (254 µm i.d. × 200 mm) was used as the first dimension, while a C18 analytical capillary column performed the mycotoxin separation in beverages. Although this second one has similarities with the first, we focused mainly on the benefits related to the link between a miniaturized/automated sample preparation device with a capillary LC–MS/MS system, which made our analysis greener. Additionally, the chromatographic efficiency could even be enhanced.

Change of Amino Acid Residues in Idiotypic Nanobodies Enhanced the Sensitivity of Competitive Enzyme Immunoassay for Mycotoxin Ochratoxin A in Cereals

Anti-idiotypic nanobodies, usually expressed by gene engineering protocol, has been shown as a nontoxic coating antigen for toxic compound immunoassays. We here focused on how to increase immunoassay sensitivity by changing the nanobody’s primary sequence. In the experiments, two anti-idiotype nanobodies against monoclonal antibody 1H2, which is specific to ochratoxin A, were obtained and named as nontoxic coating antigen 1 (NCA1) and nontoxic coating antigen 2 (NCA2). Three differences between the nanobodies were discovered. First, there are six amino acid residues (AAR) of changes in the complementarity determining region (CDR), which compose the antigen-binding site. One of them locates in CDR1 (I–L), two of them in CDR2 (G–D, E–K), and three of them in CDR3 (Y–H, Y–W). Second, the affinity constant of NCA1 was tested as 1.20 × 10⁸ L mol⁻¹, which is about 4 times lower than that of NCA2 (5.36 × 10⁸ L mol⁻¹). Third, the sensitivity (50% inhibition concentration) of NCA1 for OTA was shown as 0.052 ng mL⁻¹, which was 3.5 times lower than that of nontoxic coating antigen 2 (0.015 ng mL⁻¹). The results indicate that the AAR changes in CDR of the anti-idiotypic nanobodies, from nonpolar to polar, increasing the affinity constant may enhance the immunoassay sensitivity. In addition, by using the nontoxic coating antigen 2 to substitute the routine synthetic toxic antigen, we established an eco-friendly and green enzyme-linked immunosorbent assay (ELISA) method for rapid detection of ochratoxin A in cereals. The half-maximal inhibitory concentration (IC₅₀) of optimized ELISA was 0.017 ng mL⁻¹ with a limit of detection (LOD) of 0.003 ng mL⁻¹. The optimized immunoassay showed that the average recoveries of spiked corn, rice, and wheat were between 80% and 114.8%, with the relative standard deviation (RSD) ranging from 3.1–12.3%. Therefore, we provided not only basic knowledge on how to improve the structure of anti-idiotype nanobody for increasing assay sensitivity, but also an available eco-friendly ELISA for ochratoxin A in cereals.

Advances in Analysis and Detection of Major Mycotoxins in Foods

Mycotoxins are the most widely studied biological toxins, which contaminate foods at very low concentrations. This review describes the emerging extraction techniques and the current and alternatives analytical techniques and methods that have been used to successfully detect and identify important mycotoxins. Some of them have proven to be particularly effective in not only the detection of mycotoxins, but also in detecting mycotoxin-producing fungi. Chromatographic techniques such as high-performance liquid chromatography coupled with various detectors like fluorescence, diode array, UV, liquid chromatography coupled with mass spectrometry, and liquid chromatography-tandem mass spectrometry, have been powerful tools for analyzing and detecting major mycotoxins. Recent progress of the development of rapid immunoaffinity-based detection techniques such as immunoassays and biosensors, as well as emerging technologies like proteomic and genomic methods, molecular techniques, electronic nose, aggregation-induced emission dye, quantitative NMR and hyperspectral imaging for the detection of mycotoxins in foods, have also been presented.

A rapid HPLC-FLD method for Ochratoxin A detection in pig muscle, kidney, liver by using enzymatic digestion with MISPE extraction

Ochratoxin A (OTA) is a mycotoxin produced as a secondary metabolite by various Aspergillus and Penicillium species with nephrotoxic, carcinogenic, immunotoxic and teratogenic effects. OTA has been found in several food commodities, including cereals, beer, wine and spices. OTA can also be present in animal products (especially in pig derived products) as a result of carryover from contaminated feed. Permitted level of 1 µg/kg OTA in pig meat or pig-derived products was set in Italy, as in other countries. Key parameters which affected MISPE, should be described such as extraction efficiency and were optimized, analyzed by an isocratic HPLC-FLD method. Under the optimized conditions, for all analyzed matrices mean recovery was > 89%. Method can be applied as alternative routine procedure to detect OTA presence in pig products. Points:  *Aim of the study was to develop and validate a quantitative HPLC-FLD method based on MISPE with complex solid matrices (edible tissues) followed by chromatographic analysis.  *The new method was developed and validated in pig complex matrix and is very sensitive LOD and LOQ respectively 0.001 and 0.003 µg/kg.  *This method is relatively simple to use and with good performances. Was possible to reuse MISPE column with a "regeneration" solution, until to 7 times.

BSA-based sample clean-up columns for ochratoxin A determination in wine: Method development and validation

Analytical chromatographic techniques for mycotoxins control are well established, but they often depend on costly immunoaffinity sample clean-up. Serum albumins, particularly that from bovine origin (BSA), have stable binding affinity towards some mycotoxins, and can be cheaper alternative receptors for sample clean-up due to their wide availability. Thus, this work used BSA immobilized in agarose beads as a novel solid-phase extraction method for quantification of ochratoxin A (OTA) in wine. Constructed BSA-agarose columns could extract OTA efficiently from red wine after its dilution (4-fold) in 0.1 M Tris pH 8.0. The method was linear (R² = 0.9999) in the OTA concentration range studied (0.05 to 3.0 μg L^-1), with recovery rates above 98%. It also showed low detection (0.017 μg L^-1) and quantification (0.051 μg L^-1) limits. The efficacy of the BSA-based method was further validated by direct comparison with commercial immunoaffinity columns. Portuguese wines analyzed by both methods had agreeing results.

Fast and simple determination of moroxydine residues in pig and chicken samples by ultra-performance liquid chromatography-tandem mass spectrometry

A general solid-phase extraction (SPE) method using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for the determination of moroxydine residues in pig and chicken samples has been developed. After extraction and purification of real samples, moroxydine residues were detected using a hydrophobic interaction liquid chromatography column with an optimised mobile phase composition. The extraction reagents, the kind of SPE columns and the type of eluents were optimised to achieve the maximum extraction efficiency. The matrix effects from the animal tissue influenced the quality of the quantitative data obtained. Under the optimised conditions, the moroxydine residues in pig and chicken samples spiked at three levels (1.0 μg/kg, 5.0 μg/kg and 10.0 μg/kg) were determined with good recoveries (61.5%-105.4%) and adequate relative standard deviations (3.2%-13.0%). In pig and chicken samples, the limit of detection (LOD) was 0.3 μg/kg, and the limit of quantification (LOQ) was 1.0 μg/kg. A sufficiently linear relationship in the range of 1.0 μg/kg-20.0 μg/kg was achieved with a good correlation coefficient (R² ≥ 0.99).

Development of a Nanobody-AviTag Fusion Protein and Its Application in a Streptavidin-Biotin-Amplified Enzyme-Linked Immunosorbent Assay for Ochratoxin A in Cereal

Ochratoxin A (OTA) is a common food contaminant that threatens consumers' safety and health. A sensitive and selective biotin-streptavidin-amplified enzyme-linked immunosorbent assay (BA-ELISA) for OTA using a nanobody-AviTag fusion protein (Nb-AviTag) was developed in this study. The prokaryotic expression vector Nb28-AviTag-pAC6 for Nb-AviTag was constructed, followed by transformation to the AVB101 cells for antibody expression and in vivo biotinylation. The purified Nb28-AviTag was used to establish the BA-ELISA and the procedures for this Nb-AviTag-based BA-ELISA were optimized. The Nb-AviTag-based BA-ELISA exhibited the half maximal inhibitory concentration (IC₅₀) of 0.14 ng mL^-1 and the limit of detection (LOD = IC₁₀) of 0.028 ng mL^-1 for OTA basing on the optimized experiment parameters. The assay sensitivity was improved 4.6 times and 4.3 times compared to Nb-based ELISA, respectively. This method had LODs of 1.4 μg kg^-1 in barley, 0.56 μg kg^-1 in oats, and 0.84 μg kg^-1 in rice for OTA. The average recovery percent was in a range of 84-137%, and the relative standard derivation percent ranged from 0.64% to 7.8%. The content of OTA in contaminated cereal samples was determined by both the developed Nb-AviTag-based method and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results demonstrated that the Nb-AviTag was a robust and promising bioreceptor in highly sensitive detection of OTA and other low molecular weight compounds using BA system.

Novel haptens and monoclonal antibodies with subnanomolar affinity for a classical analytical target, ochratoxin A

Ochratoxin A is a potent toxic fungal metabolite whose undesirable presence in food commodities constitutes a problem of public health, so it is strictly regulated and controlled. For the first time, two derivatives of ochratoxin A (OTAb and OTAd) functionalized through positions other than the native carboxyl group of the mycotoxin, have been synthesized in order to better mimic, during the immunization process, the steric and conformational properties of the target analyte. Additionally, two conventional haptens making use of that native carboxyl group for protein coupling (OTAe and OTAf) were also prepared as controls for the purpose of comparison. The immunological performance in rabbits of protein conjugates based on OTAb and OTAd overcome that of conjugates employing OTAe and OTAf as haptens. After immunization of mice with OTAb and OTAd conjugates, a collection of high-affinity monoclonal antibodies to ochratoxin A was generated. In particular, one of those antibodies, the so-called OTAb#311, is very likely the best antibody produced so far in terms of selectivity and affinity to ochratoxin A.

Enhanced dispersive solid phase extraction assisted by cloud point strategy prior to fluorometric determination of anti-hepatitis C drug velpatasvir in pharmaceutical tablets and body fluids

An innovative spectrofluorometric method was developed for the analysis of a recently FDA approved anti-hepatitis C velpatasvir (VELP). The developed method was relied on dispersive solid phase extraction (dSPE) using synergistic effect of reduced graphene oxide (RGO) and cobalt hydroxide nanoparticles (CHNPs) in addition to cloud point extraction (CPE) using polyethylene glycol 6000 (PEG 6000) as non-ionic surfactant. This method combines the merits of preconcentration and interferences elimination achieved by dSPE and CPE, respectively. All relevant parameters such as surfactant concentration, ionic strength, pH, incubation time and others were thoroughly investigated and optimized. Fluorometric detection of VELP was carried out at excitation wavelength of 350 nm and emission wavelength of 415 nm. Under the optimum conditions, a linear calibration curve was achieved in the range of 0.5-45 ng mL-1. Limits of detection (LOD) and quantification (LOQ) based on three and ten times the standard deviation of the blank were 0.040 and 0.112 ng mL-1, respectively. This method was successfully applied for determination of VELP in real samples such as tablets, human plasma and urine samples with good recoveries.

High Incidence and Levels of Ochratoxin A in Wines Sourced from the United States

Ochratoxin A (OTA) is one of the most prevalent mycotoxin contaminants of food crops. Among the agricultural products consequently contaminated by OTA is wine. In the present study, a sample of wines sourced from the United States was assessed for OTA. Wines were primarily analyzed by high-performance liquid chromatography with fluorescence detection (HPLC-FD) coupled to a liquid-liquid extraction (LLE) technique which was developed and validated as a simplified sample preparation approach. More than 85% of the wines evaluated were found to contain OTA, at levels above the limit-of-detection (LOD = 0.1 µg L⁻¹), and 76% were above the limit-of-quantitation (LOQ = 0.3 µg L⁻¹) for the LLE/HPLC-FD method. More than two-thirds of the wines above the LOQ were found to exceed 1 µg L⁻¹. Complementary analysis by HPLC coupled to tandem mass spectrometry (HPLC-MS/MS) confirmed OTA in 74% of the OTA-positive wines (i.e., >LOQ by HPLC-FD). Overall, both the occurrence and measured levels of OTA were generally high, specifically relative to previous assessments of OTA in wine, and two of the wines were above the only current (European Union) regulatory limit of two parts-per-billion (ppb, ~2 µg L⁻¹). Possible trends with respect to geographical region and/or growing climate are noted. As the first assessment of U.S. wines in more than a decade, the overall high occurrence and levels of OTA in wine, and possible geographic and climatic trends, point to a need for regular surveillance of wines, as well as investigation of the relevant contributors to OTA occurrence toward mitigating contamination and exposure risks.

State-of-the-Art Chocolate Manufacture: A Review

The aroma, taste, shine, snap, smoothness, "melt-in-your-mouth" sensation, and texture are all qualities that define chocolate, and all depend on how the cocoa and the chocolate itself are processed. Postharvest handling of the cocoa (fermentation, drying, cleaning, storage, and transport) and its transformation into chocolate (roasting, grinding, conching, tempering, molding, and the addition of core and other ingredients), as well as the packaging, storage, transport, and refrigeration of the finished product all have an important influence on the characteristics of chocolate. The aim of this review was to identify and study the key factors, including microbiological aspects that affect the quality of chocolate, from harvesting the beans right up to the manufacture of the finished products.