Novel analytical procedure using a combination of hollow fiber supported liquid membrane and dispersive liquid-liquid microextraction for the determination of aflatoxins in soybean juice by high performance liquid chromatography - Fluorescence detector

Experimental-design-based optimization of dispersive liquid-liquid microextraction coupled with gas chromatography-negative-ion chemical ionization-mass spectrometry for the determination of pyrethroids in agricultural products and drinks

Pyrethroids are synthetic chemicals that account for 16% of the international insecticide market and have been shown to be of varying toxicity to different species. There are various methods available for detecting pyrethroids in agricultural products, but these products must be pre-treated to remove interference from the food matrix, such as through dispersion liquid-liquid microextraction (DLLME). This study employed two experimental design methods to optimize the continuous and discontinuous experimental parameters of DLLME and investigated whether DLLME combined with GC-NICI-MS is effective for detecting pyrethroids in agricultural products. The Taguchi design with an L9(34) orthogonal array and response surface methodology were employed to optimize the discontinuous and continuous parameters of the DLLME process, respectively. To validate the performance of GC-NICI-MS after optimized DLLME, pyrethroids in mixed standard solutions at levels ranging from 0.02 to 50.00 µg/L were measured, and the resultant calibration curves were fitted. Adequate linearity was found for the six investigated pyrethroids (r = 0.9908-0.9960). The limits of detection and quantification ranged from 0.005 to 0.035 µg/L and 0.02 to 0.1 µg/L, respectively. The proposed approach simplifies the optimization of parameters compared to reported methods and achieves considerably lower limits of detection. The concept of mixed application based on the dual experimental design method can be applied to other regulated compounds to enhance the safety of agricultural products. The feasibility of the method was confirmed by successfully detecting pyrethroids in 13 types of teas, fruit, and vegetables.

Determination of mycobiota and aflatoxin contamination in commercial bee pollen from eight provinces and one autonomous region of China

The co-occurrence of fungi and mycotoxins in various foods has been frequently reported in many countries, posing a serious threat to the health and safety of consumers. In this study, the mycobiota in five types of commercial bee pollen samples from China were first revealed by DNA metabarcoding. Meanwhile, the content of total aflatoxins in each sample was investigated by high-performance liquid chromatography with fluorescence detection. The results demonstrated that Cladosporium (0.16 %-89.29 %) was the most prevalent genus in bee pollen, followed by Metschnikowia (0-81.12 %), unclassified genus in the phylum Ascomycota (0-81.13 %), Kodamaea (0-73.57 %), and Penicillium (0-36.13 %). Meanwhile, none of the assayed aflatoxins were determined in the 18 batches of bee pollen samples. In addition, the fungal diversity, community composition, and trophic mode varied significantly among five groups. This study provides comprehensive information for better understanding the fungal communities and aflatoxin residues in bee pollen from different floral origins in China.

A simple fluorometric method for rapid screening of aflatoxins after their extraction by magnetic MOF-808/graphene oxide composite and their discrimination by HPLC

Herein, a high-performance screening tool for the selective and sensitive monitoring of aflatoxins is reported based on their great quenching effect on the blue emission of graphene quantum dots (GQDs). To make a specific determination, a pre-extraction method was also developed using a new nano-sorbent based on the surface-imprinted Zr metal-organic framework on the magnetic graphene oxide (MGO/MOF-808@MIP). The adsorbing efficiency of the prepared composite was remarkably higher than the pristine MOF-808 or bare GO. The presence of GO nanosheets, as well as nanoporous MOF-808 provided a high accessible surface area to form the MIP layer. It provided a great number of MIP sites for high efficient and rapid extraction of aflatoxins. The presence of magnetic nanoparticles in the structure of nanocomposite also facilitated the extraction process using a magnetic solid-phase extraction (MSPE) system. The combination of this specific and high-performance extraction with simple fluorometric detection caused a potent screening tool for aflatoxins. The method was able to monitor the total aflatoxins content of food samples with a linear range of 0.05-8 ng mL^-1, which was more sensitive than the fluorometric system without extraction (5-500 ng mL^-1). More developments were made by the application of a high-performance liquid chromatography (HPLC) method for the discrimination of the extracted aflatoxins. The system showed high sensitivity and selectivity and was able to detect different aflatoxins with an acceptable resolution.

Application of new N- and S-doped amorphous carbon in D-μSPE and its combination with deep eutectic solvent-based DLLME for the extraction of some mycotoxins from soymilk

A new amorphous carbon-based dispersive micro solid-phase extraction method was developed for the extraction and preconcentration of several mycotoxins from soymilk samples. The extracted analytes were concentrated by a deep eutectic solvent-based dispersive liquid-liquid microextraction method, and then, quantified by a high-performance liquid chromatography-fluorescence detector. The sorbent was prepared from β-cyclodextrin and methionine under mild conditions. The sorbent was doped by N and S, which improved its physicochemical properties. The optimization and validation of the method were performed using the "one-variable-at-a-time" method and International Council Harmonization guideline, respectively. Under the optimal conditions, low limits of detection and quantifications in the ranges of 0.08-0.56 and 0.27-1.9 ng L-1 were obtained, respectively. Also, intra- (n = 6) and inter-day (n = 6) precisions showed an acceptable repeatability of the present work as they were in the ranges of 3.9-6.2 and 4.6-8.9% at a concentration of 3 ng L-1 of each analyte, respectively. Finally, the proposed method was performed on different soymilk samples marketed in Tabriz city, and aflatoxin B1 was found in all samples. One soymilk was contaminated by ochratoxin A.

Assessment of trace levels of aflatoxins AFB1 and AFB2 in non-dairy beverages by molecularly imprinted polymer based micro solid-phase extraction and liquid chromatography-tandem mass spectrometry

A selective molecularly imprinted polymer (MIP) adsorbent was synthesised and used in a batch micro-solid phase extraction format for isolating aflatoxins (AFB1, and AFB2) from non-dairy beverages before liquid chromatography-tandem mass spectrometry determination. MIP synthesis (precipitation polymerization in 3 : 1 acetonitrile/toluene as a porogen) was performed with 5,7-dimethoxycoumarin (DMC), methacrylic acid (MAA) and divinylbenzene-80 (DVB) as a dummy template, functional monomer and cross-linker, respectively (1 : 4 : 20 molar ratio). 2,2'-Azobisisobutyronitrile (AIBN) was used as a polymerization initiator. The adsorbent MIP (50 mg) was enclosed in a cone-shaped polypropylene membrane (porous membrane protected molecularly imprinted micro-solid phase extraction), and parameters such as sample pH, mechanical (orbital-horizontal) shaking, the extraction time (loading stage), the composition of the eluting solution, and the desorption time were optimised. The highest extraction yields were obtained by using 5 mL of non-dairy beverages (pH adjusted at 6.0), and mechanical shaking (150 rpm) for 15 min. Elution was performed with 5 mL of an acetonitrile/formic acid (97.5 : 2.5) mixture under ultrasound (325 W, 35 kHz) for 15 min. After eluate evaporation to dryness and re-dissolution in 150 μL of the mobile phase, the pre-concentration factor of the method was 33.3, which yields limits of detection within the 0.085-0.207 μg L^-1 range. In addition, the current proposal was shown to be an accurate and precise method through relative standard deviation of intraday and inter-day assays below 18% and analytical recoveries in the range of 91-104%. However, the method was found to suffer from matrix effects.

Deep eutectic solvent based ultrasound assisted emulsification microextraction for preconcentration and voltammetric determination of aflatoxin B1 in cereal samples

A new and simple deep eutectic solvent based ultrasound-assisted emulsification microextraction (DES-UAEME) procedure has been developed for preconcentration and voltammetric determination of aflatoxin B1 (AFB1) in cereal products. The method is based on the acetonitrile-based extraction of AFB1 from homogenized cereal samples followed by a DES-UAEME procedure for subsequent differential pulse voltammetry (DPV) determination in a microcell. A DES composed of choline chloride and urea (ChCl-Ur) was used as the extraction solvent and electrolyte for DPV detection. Various parameters affecting the extraction efficiency of AFB1 were evaluated and optimized. Under optimum conditions the calibration graph was linear in the range of 0.2-80.0 μg L^-1 (R² = 0.9966) and the limit of detection (3S_b) was estimated to be 0.05 μg L^-1. The intra-day and inter-day precision (RSD%) for determination of 5.0 μg L^-1 AFB1 were 3.4% and 3.9%, respectively. The proposed method was also successfully applied for preconcentration and determination of AFB1 in different cereal samples and good relative recoveries were obtained over a range of 94 to 104%.

A smartphone-based dual detection mode device integrated with two lateral flow immunoassays for multiplex mycotoxins in cereals

In this study, a smartphone-based quantitative dual detection mode device, integrated with gold nanoparticles (GNPs) and time-resolved fluorescence microspheres (TRFMs) lateral flow immunoassays (LFIA) for multiplex mycotoxins in cereals were established. The most frequently used visible light and fluorescence detection modes were integrated in one device. A user-friendly application was self-written to rapidly quantify results. GNPs-LFIA and TRFMs-LFIA were used to detect aflatoxin B1 (AFB1), zearalenone (ZEN), deoxynivalenol (DON), T-2 toxin (T-2), and fumonisin B1 (FB1). The visible limits of detection (vLODs) were 10/2.5/1.0/10/0.5, 2.5/0.5/0.5/2.5/0.5 μg/kg for the two methods, respectively. The quantitative limits of detection (qLODs) were 0.59/0.24/0.32/0.9/0.27, 0.42/0.10/0.05/0.75/0.04 μg/kg, respectively. The recoveries of both LFIAs ranged from 84.0%-110.0%. A parallel analysis in 30 naturally contaminated cereal samples was conducted by liquid chromatography-tandem mass spectrometry (LC-MS/MS), the results showed good consistency, indicating the practical reliability of the established methods. The developed two smartphone-based LFIAs provide a promising technique for multiplex, highly sensitive, and on-site detection of mycotoxins.

An Automated and High-Throughput Immunoaffinity Magnetic Bead-Based Sample Clean-Up Platform for the Determination of Aflatoxins in Grains and Oils Using UPLC-FLD

Sample clean-up remains the most time-consuming and error-prone step in the whole analytical procedure for aflatoxins (AFTs) analysis. Herein, an automated and high-throughput sample clean-up platform was developed with a disposable, cost-effective immunoaffinity magnetic bead-based kit. Under optimized conditions, the automated method takes less than 30 min to simultaneously purify 20 samples without requiring any centrifugation or filtering steps. When coupled to ultra-high performance liquid chromatography with fluorescence detection, this new analysis method displays excellent accuracy and precision as well as outstanding efficiency. Furthermore, an interlaboratory study was performed in six laboratories to validate the novel protocol. Mean recovery, repeatability, reproducibility, and Horwitz ratio values were within 91.9%–107.4%, 2.5%–7.4%, 2.7%–10.6%, and 0.26%–0.90, respectively. Results demonstrate that the developed sample clean-up platform is a reliable alternative to most widely adopted clean-up procedures for AFTs in cereals and oils.

Electrospun polymer composite nanofiber-based in-syringe solid phase extraction in tandem with dispersive liquid-liquid microextraction coupled with HPLC-FD for determination of aflatoxins in soybean

A fast method based on in-syringe solid phase extraction combined with dispersive liquid-liquid microextraction was developed for extraction of aflatoxins prior to HPLC-FD. Electrospun polyurethane nanofibers doped with graphene oxide were collected on a thin metal net sheet without using a binder, placed into a filter holder between filter papers on a syringe tip and used as an efficient adsorbent for the first time. The major parameters affecting whole extraction efficiency were investigated and optimized. Under the optimum conditions, the limits of detection and the limits of quantification were in the range of 0.09-0.15 and 0.3-0.5 µg kg-1, respectively. The linear dynamic range was 0.3-1000 µg kg-1 with determination coefficients of 0.9946-0.9965. The inter- and intra-day precisions were lower than 4.3 and 7.2%, respectively. The method was successfully applied for the determination of aflatoxins B1, B2, G1, and G2 in soybeans and satisfactory relative recoveries of 76-101% were achieved.

Transfer rates of aflatoxins from herbal medicines to decoctions determined by an optimized high-performance liquid chromatography with fluorescence detection method

Objectives

This study aimed to explore the transfer rates of aflatoxins from several contaminated herbal medicines by fungi to their decoctions.

Methods

Five types of commonly used herbal medicines including Lilii Bulbus, Hordei Fructus Germinatus, Nelumbinis Semen, Polygalae Radix and Bombyx Batryticatus were selected as the examples. Raw herbal medicine samples were treated by ultrasonication-assisted extraction with 70% methanol and immunoaffinity column clean-up, and the decoctions were prepared following the commonly used boiling method with water for 2 h. Then, the optimized high-performance liquid chromatography with fluorescence detection (HPLC-FLD) method was validated for the quantitative analysis of four aflatoxins (AFG2, AFG1, AFB2 and AFB1) after postcolumn photochemical derivatization, which was proved to be reliable and sensitive.

Key findings

Aflatoxins were detected to be transferred from the herbal medicines to decoctions with significantly different transfer rates in the five types of herbal medicines. Quietly high transfer rates of 7.26–115.36% for AFG2, 4.37–26.37% for AFB1 and 9.64–47.68% for AFB2 were obtained. AFB1 as the most toxic aflatoxin expressed the lowest transfer rate, but still exhibited high amount in the samples.

Conclusions

Therefore, the monitoring of aflatoxins in herbal medicines and their decoctions is in great urgency to ensure the security of consumers taking decoctions.

A simple solvent based microextraction for high performance liquid chromatographic analysis of aflatoxins in rice samples

This paper describes the development of a simple solvent based microextraction, namely vortex assisted low density solvent-microextraction (VALDS-ME), followed by high performance liquid chromatography-fluorescence detection (HPLC-FD) for the simultaneous determination of four aflatoxins (AFs) including AFB1, AFB2, AFG1 and AFG2 in rice samples. In VALDS-ME, a mixture of low density solvents (1-octanol and toluene) was used as the extraction solvent. The extraction was rapidly achieved with the assistance of vortex agitation and phase separation was easily obtained after the addition of Na₂SO₄. The effects of various parameters on the extraction efficiency were optimized. Under the optimum conditions, high enrichment factors (42-132), low limits of detection (LODs) in the range of 0.0011-0.17μgkg^-1 and good precisions (RSDs lower than 6.2%) were obtained. AFB1 and AFG1 were detected in berry rice sample at 0.26 and 2.1μgkg^-1, respectively. The recoveries in AFs-spiked rice samples ranged from 70% to 104%. Moreover, the present method was comparable to the conventional immunoaffinity chromatography method.

Graphene oxide adsorbent based dispersive solid phase extraction coupled with multi-pretreatment clean-up for analysis of trace aflatoxins in traditional proprietary Chinese medicines

Graphene oxide (GO)-based dispersive solid phase extraction (D-SPE) method combined with multi-step preparation has been proposed for the evaluation of trace aflatoxins in proprietary Chinese medicines (PCM). After being extracted by methanol, the sample was purified based on multi-step preparation, including dehydration with MgSO₄/NaCl and cleanup with neutral alumina. Then GO was used as an adsorbent in D-SPE method for further preconcentration of aflatoxins prior to high performance liquid chromatography-fluorescence detection. The selected conditions were investigated. The Box-Behnken design (BBD) was used to optimize factors affecting adsorption procedure. Under the optimized conditions, good linear relationships had been achieved with the correlation coefficient (R²) varying from 0.9904 to 0.9990. The LODs and LOQs were ranging from 0.020 to 0.041ng/mL and 0.061 to 0.125ng/mL, respectively. The results of the recoveries were 74.0-102.7% for the four aflatoxins, while the precisions from 1.8% to 7.2% were obtained, which indicated that the method was suitable for the analysis of aflatoxins in PCM.

Simultaneous synthesis of a deep eutectic solvent and its application in liquid–liquid microextraction of polycyclic aromatic hydrocarbons from aqueous samples

New generation of solvents, named deep eutectic solvents, were simultaneously synthesized and used as an extraction solvent in a liquid–liquid microextraction method for the extraction and preconcentration of some polycyclic aromatic hydrocarbons.