Development and validation of the one-step purification method coupled to LC-MS/MS for simultaneous determination of four aflatoxins in fermented tea

Molecularly imprinted dispersive micro solid-phase extraction coupled with high-performance liquid chromatography for the determination of four aflatoxins in various foods

A new dummy template-based molecularly imprinted dispersive micro solid-phase extraction (MI-d-µSPE) coupled with HPLC-FLD developed for the simultaneous determination of four aflatoxins (B1, B2, G1, G2) in various food matrices. The synthesized MIP was used as a dispersive solid-phase extraction (dSPE) sorbent for aflatoxins extraction. The chemometric approach was used to identify the optimum conditions of dSPE. The results showed the amount of MIP sorbent (55 mg), adsorption time (12.5 min), and %ACN (75%) were significant extraction parameters. The method has a detection limit in the range of 0.059-0.208 µg kg-1 and a quantification limit in the range of 0.197-0.694 µg kg-1 for aflatoxins. The intra- and inter-day precision was less than 5%, and recoveries were 79.1-109.4%. The expanded uncertainty of the developed method was found to be 2.9-22.8%. The new MI-d-µSPE with HPLC-FLD method was applied for 37 food matrices.

Fluorescent Selectivity-Enhanced FRET Based on 3D Photonic Crystals for Multianalyte Sensing

Fluorescence resonance energy transfer (FRET) finds widespread utility in biochemical sensing, single-molecule experiments, cell physiology, and various other domains due to its inherent simplicity and high sensitivity. Nevertheless, the efficiency of energy transfer between the FRET donor and acceptor is significantly contingent on the local photonic environment, a factor that limits its application in complex systems or multianalyte detections. Here, a fluorescent selectivity-enhanced acridine orange (AO)-aflatoxins (AFs) FRET system based on a range of 3D topological photonic crystals (PCs) was developed with the aim of enhancing the selectivity and discrimination capabilities of FRET. By exploring the angle-dependent characteristics of the photonic stopband, the stopband distribution across different 3D topological PCs pixels was investigated. This approach led to selective fluorescence enhancement in PCs that matched the stopbands, enabling the successful discrimination of six distinct aflatoxins and facilitating complex multianalysis of moldy food samples. In particular, the stopband, which was strategically positioned within the blue-purple structural color range, exhibited a strong alignment with the fluorescence peaks of both the FRET donor and acceptor. This alignment allowed the 3D three-pointed star PCs to be effectively employed for the identification of mixed samples containing six distinct aflatoxins as well as the detection of real aflatoxin samples present in moldy potatoes, bread, oats, and peanuts. Impressively, this approach achieved a remarkable accuracy rate of 100%. This innovative strategy not only presents a novel avenue for developing a multitarget discrimination analysis system but also offers a convenient pretreatment method for the quantitative detection of various aflatoxins.

Novel functional DNA-linked immunosorbent assay for aflatoxin B1 with dual-modality based on hybrid chain reaction

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins, which is frequently detected in agricultural products. Herein, a novel functional DNA -linked immunosorbent assay (DLISA) with dual-modality based on hybrid chain reaction (HCR) has been successfully developed for ultrasensitive detection of AFB1. The strategy relies on AFB1 immune-bridged occurrence of HCR and the salt-induced aggregation of gold nanoparticles (AuNPs). An aptamer-initiator stand (Apt-Ini stand) is designed for the AFB1 recognition and the activation of HCR, which can recognize the matched hairpins and cause the crossing-opening of H1 and H2, producing a long double-stranded DNA polymer. The addition of SYBR Green I achieves the fluorescent signal output. Remaining less DNA hairpins were added and stuck on the surface of AuNPs, which were insufficient to protect the AuNPs, resulting in the salt-induced aggregation with the color change from red to blue. The dual-modality provides limits of detections of 1.333 × 10-14 g/mL and 2.471 × 10-15 g/mL, respectively. This DLISA with dual-modality provides not only a colorimetry that can meet the needs of on-the-spot preliminary inspection, but also a fluorescence assay that can acquire the precise results.

Quantitative analysis and survey of 9,10-anthraquinone contaminant in Chinese Liupao tea

Recently, 9,10-anthraquinone (AQ) contamination in Chinese Liupao tea has attracted much attention because the tea for export must meet the EU limit (10 µg kg^-1). In this study, a method was developed in which the sample was extracted with n-hexane-acetone solution, then purified with Florisil adsorbent, detected by GC-MS/MS and contamination levels of AQ determined using an internal standard. This method was found to be more suitable for Liupao tea and other dark tea complex substrates than the QuEChERS procedure. The sample pre-treatment method was optimized with respect to extraction reagent and clean-up column adsorbent and n-hexane-acetone selected as the optimal extraction solvent. When the content of Florisil in the column was 1.0 g, the optimum clean-up was achieved. The new method reduced the limit of quantification (LOQ) of AQ to 10 μg kg^-1, and accuracy was also further improved. The recovery of AQ-fortified tea samples containing 20-100 µg·kg^-1 was 94.5-100.4%, and the relative standard deviation (RSD) was less than 1.3%. In a small survey, 98 Liupao tea samples on the market were tested by the new method. It was found that 61 samples were positive (occurrence rate 63.3%), and thus exceeded the EU limit (10 µg kg^-1). This study also found that the contamination of AQ in Liupao tea increased with the length of ageing. The source of AQ in the Liupao tea ageing process will be the focus of further research.

Zanthoxylum bungeanum as a natural pickling spice alleviates health risks in animal-derived foods via up-regulating glutathione S-transferase, down-regulating cytochrome P450 1A

Endogenous aflatoxin B1 (AFB1) was quantified in five hundred and forty Hengshan goat meat samples (0.00 ± 23.09 μg kg^-1). Zanthoxylum bungeanum (Z. bungeanum), as a natural pickling spice, can ameliorate the flavor of animal-derived food (goat meat). Yet, considering the direct administration of Z. bungeanum in AFB1-contaminated goat meat, the degradation mechanisms of AFB1 remain elusive. Here, UHPLC-Q-Orbitrap HRMS-based integrative metabolomics (LOQ: 1.74-59.54 μg kg^-1) and proteomics analyses were executed to determine the effects of Z. bungeanum in the biotransformation of AFB1. Z. bungeanum (1.50 %, w/w) application mediated the metabolism of xenobiotics by cytochrome P450, significantly down-regulated cytochrome P450 1A and stimulated the up-regulation of glutathione S-transferase levels in AFB1-contaminated goat meat, leading to degradation of AFB1 (20.00-3.39 μg kg^-1). Metabolomics assays indicated that Z. bungeanum up-regulated l-histidine (1.43-2.21 mg kg^-1) and l-arginine, manifesting potential applications for the contribution of Z. bungeanum to the nutritional value of goat meat.

One sample multi-point calibration curve as a novel approach for quantitative LC-MS analysis: the quantitation of six aflatoxins in milk and oat-based milk as an example

Preparing of calibration curves are critical steps for accurate quantitative LC-MS bioanalysis. Traditional multi-sample external calibration curve (MSCC) is labor-intensive and prone to error. In this study, a novel strategy of one sample multi-point calibration curve (OSCC) using multiple isotopologue reaction monitoring (MIRM) was proposed and validated using LC-MS for the quantitation of six aflatoxins in milk and oat-based milk samples. The developed MIRM-OSCC methodology is comprehensively validated and the results indicated that the established method exhibits good performance in selectivity, sensitivity, accuracy and precision. Furthermore, the OSCC could realize sample dilution by monitoring the MIRM channel with less intensity for samples beyond the upper limit of quantification, without the need of sample dilution, which improves the assay throughput. Considering the advantages of excluding the MSCC preparation and sample dilution in OSCC, this strategy can be widely applied in various fields such as drugs, food safety and environmental analysis.

Stability Evaluation of Aflatoxin B1 Solution Certified Reference Material via Ultra-High Performance Liquid Chromatography Coupled with High-Resolution Mass Spectrometry

Aflatoxin B₁ (AFB₁) solution certified reference materials (CRMs) have been widely utilized in the measurements of AFB₁ contaminations in foods and agricultural products. It is of great importance to evaluate the stability of AFB₁ solution CRMs in different matrices for their practical applications. In this study, the stability of AFB₁ solution CRM was investigated and its degradation products under various conditions were elucidated using ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry for the first time. Exposure to high temperatures and UV light irradiation accelerated the degradation of AFB₁ solution significantly, and the degradation products were largely dependent on the solvents. Two degradation pathways were proposed based on the degradation products. The addition reaction, oxidation reaction, and modification of the methoxy group are the major processes involved in the degradation of the AFB₁ solution. The results of this study indicate that the property value of the acetonitrile solution of AFB₁ can be well retained when it is stored at temperatures lower than 60 °C, and the exposure to UV light irradiation is avoided.

Recent advances in simultaneous detection strategies for multi-mycotoxins in foods

Mycotoxin contamination has become a challenge in the field of food safety testing, given the increasing emphasis on food safety in recent years. Mycotoxins are widely distributed, in heavily polluted areas. Food contamination with these toxins is difficult to prevent and control. Mycotoxins, as are small-molecule toxic metabolites produced by several species belonging to the genera Aspergillus, Fusarium, and Penicillium growing in food. They are considered teratogenic, carcinogenic, and mutagenic to humans and animals. Food systems are often simultaneously contaminated with multiple mycotoxins. Due to the additive or synergistic toxicological effects caused by the co-existence of multiple mycotoxins, their individual detection requires reliable, accurate, and high-throughput techniques. Currently available, methods for the detection of multiple mycotoxins are mainly based on chromatography, spectroscopy (colorimetry, fluorescence, and surface-enhanced Raman scattering), and electrochemistry. This review provides a comprehensive overview of advances in the multiple detection methods of mycotoxins during the recent 5 years. The principles and features of these techniques are described. The practical applications and challenges associated with assays for multiple detection methods of mycotoxins are summarized. The potential for future development and application is discussed in an effort, to provide standards of references for further research.

Mycotoxins in Wheat Flours Marketed in Shanghai, China: Occurrence and Dietary Risk Assessment

The risk of exposure to mycotoxins through the consumption of wheat flours has long been a concern. A total of 299 wheat flours marketed in Shanghai Province of China were surveyed and analyzed for the co-occurrence of 13 mycotoxins through an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. The detection rates of mycotoxins in wheat flours ranged from 0.7~74.9% and their average contamination levels in wheat flours (0.2~57.6 µg kg^-1) were almost lower than the existing regulations in cereals. However, their co-contamination rate was as high as 98.1%, especially Fusarium and Alternaria mycotoxins. Comparative analysis of different types of wheat flours showed that the average contamination levels in refined wheat flours with low-gluten were lower. Based on these contamination data and the existing consumption data of Shanghai residents, point evaluation and the Monte Carlo assessment model were used to preliminarily evaluate the potential dietary exposure risk. The probable daily intakes of almost all mycotoxins, except for alternariol, were under the health-based guidance values for 90% of different consumer groups. Health risks of dietary exposure to alternariol should be a concern and further studied in conjunction with an internal exposure assessment.

Dispersive micro solid phase extraction based ionic liquid functionalized ZnO nanoflowers couple with chromatographic methods for rapid determination of aflatoxins in wheat and peanut samples

Aflatoxins (AFs) contaminate agricultural products in a wide range of ways during their harvesting, storage and transport. Therefore, the detection of AFs has certain practical significance. Herein, a dispersive micro solid phase extraction (D-µSPE) technology was constructed based on 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF₆]) fabricated ZnO nanoflowers for AFs extraction from food matrix before HPLC procedure. The key parameters affecting the extraction efficiency were studied. Under optimal experimental conditions, the method showed excellent linearity with high correlation coefficients (≥0.994). LOD and LOQ were 0.034 and 0.114 μg/kg for AFB1, 0.024 and 0.082 μg/kg for AFB2, 0.067 and 0.226 μg/kg for AFG1 and 0.025 and 0.084 μg/kg for AFG2. The recovery of actual samples spiked with analytes (at 5, 15 and 20 μg/kg) were from 93.8 to 105.1%. Overall, an accurate AFs analysis method was developed and could be applied to the determination of AFs in various food and agricultural products.

Electrochemical immunosensor based on AuNPs/Zn/Ni-ZIF-8-800@graphene for rapid detection of aflatoxin B1 in peanut oil

Peanut oil is a basic food raw material in life. However, aflatoxin contamination in peanut oil is considered to be one of the most serious food safety problems in the world. Based on AuNPs/Zn/Ni-ZIF-8-800@graphene composite, a simple, efficient and sensitive electrochemical immunosensor was developed to detect aflatoxin B1 (AFB1) in peanut oil. The bare glassy carbon electrode was modified by graphene, bimetallic organic framework material (Zn/Ni-ZIF-8-800), chitosan and gold nanoparticles. The electrochemical immunosensor was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) and cyclic voltammetry (CV), and the electrochemical signal changes after antibody and AFB1 binding were investigated in detail. Under the optimal conditions, the linear range of the electrochemical immunosensor was 0.18-100 ng/mL, and the detection limit was 0.18 ng/mL. In addition, the prepared sensor has high selectivity and long-term stability, which lays a foundation for the simple, rapid and sensitive detection of AFB1 in peanut oil.

Mycotoxins along the tea supply chain: A dark side of an ancient and high valued aromatic beverage

ABSTRACTSTea (Camellia sinensis L.) is a high valued beverage worldwide since ancient times; more than three billion cups of tea are consumed each day. Leaf extracts of the plant are used for food preservation, cosmetics, and medicinal purposes. Nevertheless, tea contaminated with mycotoxins poses a serious health threat to humans. Mycotoxin production by tea fungi is induced by a variety of factors, including poor processing methods and environmental factors such as high temperature and humidity. This review summarizes the studies published to date on mycotoxin prevalence, toxicity, the effects of climate change on mycotoxin production, and the methods used to detect and decontaminate tea mycotoxins. While many investigations in this domain have been carried out on the prevalence of aflatoxins and ochratoxins in black, green, pu-erh, and herbal teas, much less information is available on zearalenone, fumonisins, and Alternaria toxins. Mycotoxins in teas were detected using several methods; the most commonly used being the High-Performance Liquid Chromatography (HPLC) with fluorescence detection, followed by HPLC with tandem mass spectrometry, gas chromatography and enzyme-linked immunosorbent assay. Further, mycotoxins decontamination methods for teas included physical, chemical, and biological methods, with physical methods being most prevalent. Finally, research gaps and future directions have also been discussed.

Application of a Validated Method for the Identification and Quantification of Mycotoxins in Wines Using UPLC-MS/MS

The aim of the present study was to develop a rapid, simple and reliable method for the identification and quantification of six mycotoxins in wine using liquid chromatography with electrospray ionization tandem mass spectrometry. The analytical method was fully validated, and calibration curves were made with correlation coefficients >0.9970. A short analysis time and acceptable extraction efficiency were achieved by a direct extraction method of analytes (ochratoxin A, aflatoxin B1, B2, G1, G2 and Zearalenone) with acetonitrile. LOD values were from 0.03 to 0.27 μg kg−1, and LOQ values were from 0.08 to 0.81 μg kg−1, with recoveries at various values from 77 to 108%. The expanded uncertainty was 5–21% expressed at a coverage level of k = 2, at a confidence level of approximately 95%. The performance criteria of the method were fully met according to European legislation (EC) 401/2006. The method was successfully applied to wine samples from Cyprus. The method was simple, low cost, quick, accurate, and sensitive.

Development of a Novel UPLC-MS/MS Method for the Simultaneous Determination of 16 Mycotoxins in Different Tea Categories

The contamination of potential mycotoxins in tea production and consumption has always been a concern. However, the risk monitoring on multiple mycotoxins remains a challenge by existing methods due to the high cost and complex operation in tea matrices. This research has developed a simple ultra-performance liquid chromatography-tandem mass spectrometry strategy based on our homemade purification column, which can be applied in the detections of mycotoxins in complex tea matrices with high-effectively purifying and removing pigment capacity for 16 mycotoxins. The limits of detection and the limits of quantification were in the ranges of 0.015~15.00 and 0.03~30.00 µg·kg⁻¹ for 16 mycotoxins, respectively. Recoveries from mycotoxin-fortified tea samples (0.13~1200 µg·kg⁻¹) in different tea matrices ranged from 61.27 to 118.46%, with their relative standard deviations below 20%. Moreover, this method has been successfully applied to the analysis and investigation of the levels of 16 mycotoxins in major categories of tea and the monitoring of multiple mycotoxins in processed samples of ripened Pu-erh. In conclusion, the proposed strategy is simple, effective, time-saving, and low-cost for the determination of a large number of tea samples.