HPLC determination of aflatoxin M1 in liquid milk and milk powder using solid phase extraction on OASIS HLB

Method development with high-throughput enhanced matrix removal followed by UHPLC-QqQ-MS/MS for analysis of grape polyphenol metabolites in human urine

Grape and grape derived products contain many bioactive phenolics which have a variety of impacts on health. Following oral ingestion, the phenolic compounds and their metabolites may be detectable in human urine. However, developing a reliable method for the analysis of phenolic compounds in urine is challenging. In this work, we developed and validated a new high-throughput, sensitive and reproducible analytical method for the simultaneous analysis of 31 grape phenolic compounds and metabolites using Oasis PRiME HLB cleanup for sample preparation combined with ultra-performance liquid chromatography with triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). Using this new method, the accuracy achieved was 69.3 % ∼ 134.9 % (except for six compounds), and the recovery achieved was 52.4 % ∼ 134.7 % (except for two very polar compounds). For each of the 31 target analytes, the value of intra-day precision was less than 14.3 %. The value of inter-day precision was slightly higher than intra-day precision, with a range of 0.7 % ∼ 19.1 %. We report for the first time on the effect of gender and BMI on the accuracy and recovery of human urine samples, and results from analysis of variance (ANOVA), and principal component analysis (PCA) indicated there was no difference in the value of accuracy and recovery between different gender or BMI (>30) using our purposed cleanup and UHPLC-QqQ-MS/MS method. Overall, this newly developed method could serve as a powerful tool for analyzing grape phenolic compounds and metabolites in human urine samples.

Food authentication, current issues, analytical techniques, and future challenges: A comprehensive review

Food authentication and contamination are significant concerns, especially for consumers with unique nutritional, cultural, lifestyle, and religious needs. Food authenticity involves identifying food contamination for many purposes, such as adherence to religious beliefs, safeguarding health, and consuming sanitary and organic food products. This review article examines the issues related to food authentication and food fraud in recent periods. Furthermore, the development and innovations in analytical techniques employed to authenticate various food products are comprehensively focused. Food products derived from animals are susceptible to deceptive practices, which can undermine customer confidence and pose potential health hazards due to the transmission of diseases from animals to humans. Therefore, it is necessary to employ suitable and robust analytical techniques for complex and high-risk animal-derived goods, in which molecular biomarker-based (genomics, proteomics, and metabolomics) techniques are covered. Various analytical methods have been employed to ascertain the geographical provenance of food items that exhibit rapid response times, low cost, nondestructiveness, and condensability.

Hollow-structured molecularly imprinted polymers enabled specific enrichment and highly sensitive determination of aflatoxin B1 and sterigmatocystin against complex sample matrix

The biotoxins with high toxicity have the potential to be manufactured into biochemical weapons, seriously threatening international public security. Developing robust and applicable sample pretreatment platforms and reliable quantification methods has been recognized as the most promising and practical approach to solving these problems. Through the integration of the hollow-structured microporous organic networks (HMONs) as the imprinting carriers, we proposed a molecular imprinting platform (HMON@MIP) with enhanced adsorption performance in terms of specificity, imprinting cavity density as well as adsorption capacity. The HMONs core of MIPs provided a hydrophobic surface that enhanced the adsorption of biotoxin template molecules during the imprinting process, resulting in an increased imprinting cavity density. The HMON@MIP adsorption platform could produce a series of MIP adsorbents by changing the biotoxin template, such as aflatoxin and sterigmatocystin, and showed promising generalizability. The limits of detection (LOD) of the HMON@MIP-based preconcentration method for AFT B1 and ST were 4.4 and 6.7 ng L^-1, respectively, and the method was applicable to food sample with satisfied recoveries of 81.2-95.1%. And the specific recognition and adsorption sites left on HMON@MIP by the imprinting process can achieve outstanding selectivity for AFT B1 and ST. The developed imprinting platforms hold great potential for application in the identification and determination of various food hazards in complex food sample matrices and contribute to precise food safety inspection.

Simultaneous Dual-Sensing Platform Based on Aptamer-Functionalized DNA Hydrogels for Visual and Fluorescence Detection of Chloramphenicol and Aflatoxin M1

In this study, a chloramphenicol and aflatoxin M1 aptamer-functionalized DNA hydrogel was designed for the simultaneous detection of chloramphenicol and aflatoxin M1 for the first time. The acrydite-modified chloramphenicol aptamer sequence was used to synthesize the DNA hydrogel and for visual detection of chloramphenicol depending on the gel-to-sol transition of the target-responsive DNA hydrogel. The DNA hydrogel formulation was set as follows: 60% of each linear polyacrylamide-DNA conjugate and 40% of acrylamide and chloramphenicol aptamer/DNA strand-1 at a molar ratio of 1:1, and the lowest concentration of chloramphenicol leading to gel dissociation was 1.0 nM at 25 °C. Furthermore, the formalized aptamer-functionalized DNA hydrogel was used to detect aflatoxin M1 by measuring the recovery of the fluorescence signal that was quenched when the FAM-labeled aflatoxin M1 aptamer and BHQ1-labeled DNA strand-2 were hybridized to form a double-stranded DNA in the network of hydrogel. The detection platform was successfully applied to the detection of chloramphenicol and aflatoxin M1, both in aqueous solution and in milk. The aptamer-functionalized DNA hydrogel had detection (LOD) and quantification limits (LOQ) for aflatoxin M1 as 1.7 and 5.2 nM, respectively. Using two aptamer sequences with high affinity and specificity, the dual-sensing platform based on the DNA hydrogel achieved higher selectivity for chloramphenicol and aflatoxin M1, which demonstrated its potential as a reliable simultaneous detection platform against two different targets for monitoring food safety.

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.

Aptamer-Based Fluorescence Quenching Approach for Detection of Aflatoxin M1 in Milk

Aflatoxin M1 (AFM1), one of the most toxic mycotoxins, is a feed and food contaminant of global concern. In this study, we developed a fast and simple method for detection of AFM1 based on a structure-switching signaling aptamer. This aptasensor is based on the change in fluorescence signal due to formation of an AFM1/aptamer complex. To generate the aptasensor, the specific aptamer was modified with FAM (carboxyfluorescein), and their complementary DNAs (cDNA) were modified with a carboxytetramethylrhodamine (TAMRA) quenching group. In the absence of AFM1, the aptamers were hybridized with cDNA, resulting in quenching of the aptamer fluorescence due to the proximity of the aptamer's fluorophore to the quenching group on the cDNA. On the other hand, in the presence of AFM1, a structural switch in the aptamer was induced by formation of an AFM1/aptamer complex. Changes in the structure of the aptamer led to the release of the cDNA, causing the generation of a fluorescence signal. Thus, AFM1 concentrations could be quantitatively monitored based on the changes in fluorescences. Under optimized conditions, this assay exhibited a linear response to AFM1 in the range of 1-100 ng/mL and a limit of detection of 0.5 ng/mL was calculated. This proposed aptasensor was applied to milk samples spiked with a dilution series of AFM1, yielding satisfactory recoveries from 93.4 to 101.3%. These results demonstrated that this detection technique could be useful for high-throughput and quantitative determination of mycotoxin levels in milk and dairy products.

Detection of Aflatoxins in Different Matrices and Food-Chain Positions

Aflatoxins, produced mainly by filamentous fungi Aspergillus flavus and Aspergillus parasiticus, are one of the most carcinogenic compounds that have adverse health effects on both humans and animals consuming contaminated food and feed, respectively. Aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2) as well as aflatoxin G1(AFG1) and aflatoxin G2 (AFG2) occur in the contaminated foods and feed. In the case of dairy ruminants, after the consumption of feed contaminated with aflatoxins, aflatoxin metabolites [aflatoxin M1 (AFM1) and aflatoxin M2 (AFM2)] may appear in milk. Because of the health risk and the official maximum limits of aflatoxins, there is a need for application of fast and accurate testing methods. At present, there are several analytical methods applied in practice for determination of aflatoxins. The aim of this review is to provide a guide that summarizes worldwide aflatoxin regulations and analytical methods for determination of aflatoxins in different food and feed matrices, that helps in the decision to choose the most appropriate method that meets the practical requirements of fast and sensitive control of their contamination. Analytical options are outlined from the simplest and fastest methods with the smallest instrument requirements, through separation methods, to the latest hyphenated techniques.

Aptamer-Based Biosensor for Detection of Mycotoxins

Mycotoxins are a large type of secondary metabolites produced by fungi that pose a great hazard to and cause toxic reactions in humans and animals. A majority of countries and regulators, such as the European Union, have established a series of requirements for their use, and they have also set maximum tolerance levels. The development of high sensitivity and a specific analytical platform for mycotoxins is much in demand to address new challenges for food safety worldwide. Due to the superiority of simple, rapid, and low-cost characteristics, aptamer-based biosensors have successfully been developed for the detection of various mycotoxins with high sensitivity and selectivity compared with traditional instrumental methods and immunological approaches. In this article, we discuss and analyze the development of aptasensors for mycotoxins determination in food and agricultural products over the last 11 years and cover the literatures from the first report in 2008 until the present time. In addition, challenges and future trends for the selection of aptamers toward various mycotoxins and aptasensors for multi-mycotoxins analyses are summarized. Given the promising development and potential application of aptasensors, future research studies made will witness the great practicality of using aptamer-based biosensors within the field of food safety.

A Novel Graphene Oxide-Based Aptasensor for Amplified Fluorescent Detection of Aflatoxin M1 in Milk Powder

In this paper, a rapid and sensitive fluorescent aptasensor for the detection of aflatoxin M1 (AFM1) in milk powder was developed. Graphene oxide (GO) was employed to quench the fluorescence of a carboxyfluorescein-labelled aptamer and protect the aptamer from nuclease cleavage. Upon the addition of AFM1, the formation of an AFM1/aptamer complex resulted in the aptamer detaching from the surface of GO, followed by the aptamer cleavage by DNase I and the release of the target AFM1 for a new cycle, which led to great signal amplification and high sensitivity. Under optimized conditions, the GO-based detection of the aptasensor exhibited a linear response to AFM1 levels in a dynamic range from 0.2 to 10 μg/kg, with a limit of detection (LOD) of 0.05 μg/kg. Moreover, the developed aptasensor showed a high specificity towards AFM1 without interference from other mycotoxins. In addition, the technique was successfully applied for the detection of AFM1 in infant milk powder samples. The aptasensor proposed here offers a promising technology for food safety monitoring and can be extended to various targets.

Determination of aflatoxin M1 using an aptamer-based biosensor immobilized on the surface of dendritic fibrous nano-silica functionalized by amine groups

Aflatoxins are potential food pollutants produced by fungi. Among them, aflatoxin M1 (AF M1) is the most toxic. A great deal of concern is associated with AF M1 toxicity. Aflatoxins are potential food pollutants produced by fungi. Among them, aflatoxin M1 (AF M1) is the most toxic. A great deal of concern is associated with AF M1 toxicity. In the present work, a novel aptamer-based bioassay was developed for monitoring aflatoxin M1 (AF M1) in real samples. A chitosan-modified graphene quantum dot (GQD-CS) nanocomposite was used as a biocompatible substrate coated with dendritic fibrous nanosilica functionalized by amine groups (KCC-1-NH₂-Tb). Accordingly, an innovative biocompatible polymeric matrix was prepared for aptamer immobilization. The unique oligonucleotide of AF M1 (5'-ATC CGT CAC ACC TGC TCT GAC GCT GGG GTC GAC CCG GAG AAA TGC ATT CCC CTG TGG TGT TGG CTC CCG TAT) labelled by toluidine blue was immobilized on the engineered interface. Hence, a novel aptamer-based bioassay was formed for the highly sensitive quantitation of AF M1 using cyclic voltammetry and differential pulse voltammetry techniques. The structure and morphology of GQDs-CS/KCC-1-NH₂-Tb was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, atomic force and scanning electron microscopy and energy-dispersive X-ray spectroscopy. The toxicity tests, which were performed by MTT assays, revealed the biocompatible nature of KCC-1-NH₂-Tb. The engineered aptasensor demonstrated excellent behaviour toward the determination of AF M1, where the low limit of quantification was 10 fM. The proposed aptamer-based bioassay was successfully used for the monitoring of AF M1 in milk samples. This work provides a beneficial reference for the sensing of other toxins in food/pharmaceutical assays and veterinary medicine.

Determination of 4-Hexylresorcinol in Shrimp Samples by Solid Phase Extraction Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

A method for the rapid determination of 4-hexylresorcinol (4-HR) residue in shrimp by solid phase extraction (SPE) ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established. 4-HR was extracted twice with methanol, and the extract was formulated into methanol-water solution (1:1). After being cleaned up and concentrated by a PRIME HLB solid phase extraction column, the sample was analyzed by UPLC-MS/MS and quantitatively determined by an external standard method. The separation was performed with a gradient system consisting of water and acetonitrile as the mobile phase. Monitoring was performed by electrospray ionization (ESI) in negative ion mode using multiple ion reaction monitoring (MRM). Good linearity was obtained in the concentration range of 1.0⁻100.0 μg/L, with correlation coefficients larger than 0.999. The limit of detection (LOD) was 0.25 μg/kg and the limit of quantification (LOQ) was 0.80 μg/kg. The average recoveries of 4-HR at spiked concentrations of 2.40, 6.40 and 16 μg/kg ranged from 81.35% to 94.68% with the relative standard deviations (n = 6) from 3.57% to 6.86%. The results showed that the method is simple, fast, sensitive, reliable, and reproducible; thus, it could be used as a rapid confirmation and quantitative analysis method of 4-HR residue in aquatic products.

Occurrence of aflatoxin M1 in milk samples from Italy analysed by online-SPE UHPLC-MS/MS

The occurrence of aflatoxin M1 in 69 milk samples collected in a south region of Italy in 2016 was evaluated. The samples were analysed using an automated method based on online SPE coupled with UHPLC tandem mass spectrometry. After a salt induced liquid-liquid extraction with acetonitrile to remove protein from milk, the extract was diluted with water and analysed using an automated online SPE MS/MS method. Among the analysed samples no one had AFM1 higher than the legally allowable limits whereas 71.4% of the other analysed samples were above the LOD of the method. The highest contamination level of AFM1 was found in pasteurised milk (44.39 ng kg^-1). The results show the worrying and widespread of AFM1 contamination, highlighting the necessity of monitoring studies in order to evaluate the reduction of the maximum legal limit.

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.

Determination of aflatoxin M1 in milk and dairy products using high performance liquid chromatography-fluorescence with post column photochemical derivatization

The determination of aflatoxin M₁ in milk using high performance liquid chromatography with photochemical post-column derivatization and fluorescence detection is described. The samples were first extracted and clean-up using the immunoaffinity AFLATEST column originally targeted for aflatoxins B₁, B₂, G₁ and G₂. The separation of aflatoxin M₁ were performed using C18 Hypersil gold (150mm×4.6mm, 5μm) column at 40°C under isocratic elution. Fluorescence detector (FLD) was set at 360nm and 440nm as excitation and emission, respectively. The use of methanol to replace acetonitrile as the mobile phase resulted in ∼67% peak area enhancement of AFM₁. The limit of detection (LOD) and quantification (LOQ) of the analytical method after post-column derivatization without evaporation/reconstitution with mobile phase was 0.0085μgL^-1 and 0.025μgL^-1 respectively. However, LOD and LOQ improved to 0.002 and 0.004μgL^-1 respectively with the addition of evaporation/reconstitution step. The method was statistically validated, showing linear response (R²>0.999), good recoveries (85.2-107.0%) and relative standard deviations (RSD) were found to be ≤7%. The proposed method was applied to determine AFM₁ contamination in various types of milk and milk products. Only 2 samples were contaminated with aflatoxin M₁ (10% incidence). However, the contamination level is below the Malaysian and European legislation limits.

Development of Methods for Determination of Aflatoxins

Aflatoxins can cause damage to the health of humans and animals. Several institutions around the world have established regulations to limit the levels of aflatoxins in food, and numerous analytical methods have been extensively developed for aflatoxin determination. This review covers the currently used analytical methods for the determination of aflatoxins in different food matrices, which includes sampling and sample preparation, sample pretreatment methods including extraction methods and purification methods of aflatoxin extracts, separation and determination methods. Validation for analysis of aflatoxins and safety considerations and precautions when doing the experiments are also discussed.

A qPCR aptasensor for sensitive detection of aflatoxin M1

Aflatoxin M1 (AFM1), one of the most toxic mycotoxins, imposes serious health hazards. AFM1 had previously been classified as a group 2B carcinogen [1] and has been classified as a group 1 carcinogen by the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) [2]. Determination of AFM1 thus plays an important role for quality control of food safety. In this work, a sensitive and reliable aptasensor was developed for the detection of AFM1. The immobilization of aptamer through a strong interaction with biotin-streptavidin was used as a molecular recognition element, and its complementary ssDNA was employed as the template for a real-time quantitative polymerase chain reaction (RT-qPCR) amplification. Under optimized assay conditions, a linear relationship (ranging from 1.0 × 10(-4) to 1.0 μg L(-1)) was achieved with a limit of detection (LOD) down to 0.03 ng L(-1). In addition, the aptasensor developed here exhibits high selectivity for AFM1 over other mycotoxins and small effects from cross-reaction with structural analogs. The method proposed here has been successfully applied to quantitative determination of AFM1 in infant rice cereal and infant milk powder samples. Results demonstrated that the current approach is potentially useful for food safety analysis, and it could be extended to a large number of targets.

Aflatoxin M1 in milk and milk products: a short review

Aflatoxin M1 (AFM1) is associated with carcinogenicity, genotoxicity, mutagenicity, and teratogenicity and as a result, represents a human health problem worldwide. This review will detail the toxicity, analytical methodology, occurrence, and prevention and control of AFM1 in milk and milk products. The probable daily intakes (PDI) per bodyweight (bw) worldwide ranged from 0.002 to 0.26 ng/kg bw/day for AFM1. Nevertheless, the high occurrence of AFM1 demonstrated in this review establishes the need for monitoring to reduce the risk of toxicity to humans. The recommended extraction method of AFM1 from milk is liquid-liquid with acetonitrile because of the acceptable recoveries (85-97%), compatibility with the environment, and cleanest extracts. The recommended analytical technique for the determination of AFM1 in milk is the high performance-liquid chromatography-fluorescence detector (HPLC-FLD), achieving a 0.001 µg/kg detection limit. The HPLC-FLD is the most common internationally recognised official method for the analysis of AFM1 in milk. The suggested extraction and analytical method for cheese is dichloromethane (81-108% recoveries) and ELISA, respectively. This review reports the projected worldwide occurrence of AFM1 in milk of 2010-2015. Of the 7,841 samples, 5,873 (75%) were positive for AFM1, 26% (2,042) exceeded the maximum residue levels (MRL) of 0.05 µg/kg defined by the European Union and 1.53% (120) exceeded the MRL of 0.5 µg/kg defined by the US Food and Drug Administration. The most effective way of preventing AFM1 occurrences is to reduce contamination of AFB1 in animal feed using biological control with atoxigenic strains of Aspergillus flavus, proper storage of crops, and the addition of binders to AFB1-contaminated feed. Controllable measures include the addition of binders and use of biological transforming agents such as lactic acid bacteria applied directly to milk. Though the one accepted method for the control of AFM1 in milk and milk products is the enforcement of governmental MRL.

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.

Simultaneous determination of aflatoxin B1 and M1 in milk, fresh milk and milk powder by LC-MS/MS utilising online turbulent flow chromatography

A novel, fully automated method based on dual-column switching using online turbulent flow chromatography followed by LC-MS/MS was developed for the determination of aflatoxin B1 and M1 in milk, fresh milk and milk powder samples. After ultrasound-assisted extraction, samples were directly injected into the chromatographic system and the analytes were concentrated on the clean-up loading column. Through purge switch, analytes were transferred to the analytical column for subsequent detection by mass spectrometry. Different types of TurboFlow(TM) columns, transfer flow rates and transfer times were optimised. Method limits of detection obtained for AFB1 and AFM1 were 0.05 μg kg(-1), and limits of quantification were 0.1 μg kg(-1). Recoveries of aflatoxin B1 and M1 were in range of 81.1-102.1% for all samples. Matrix effects of aflatoxin B1 and M1 were in range of 63.1-94.3%. The developed method was successfully used for the analysis of aflatoxin B1 and M1 in real samples.

Recent mycotoxin survey data and advanced mycotoxin detection techniques reported from China: a review

Mycotoxin contamination in agro-food systems has been a serious concern over the last few decades in China, where the Ministry of Health has set maximum limits for mycotoxins in different agro-products. Overall survey data show that aflatoxin contamination in infant cereals, edible oils, raw milk, ginger and its related products are far below Chinese regulatory limits. The absence of aflatoxin M1 contamination in infant milk powders indicates a high standard of control. Aflatoxins in liquorice roots and lotus seeds have been reported for the first time. For deoxynivalenol, high levels were found in wheat grown in the Yangtze Delta region, which is more prone to rainfall, supporting Fusarium infection. The emerging mycotoxins beauvericins and enniatins have been reported in the medicinal herbs in China. Ochratoxin A in wine was below the European Union regulatory limits, but fumonisins in maize need to be monitored and future regulatory control considered. Overall from all the survey data analysed in this review, it can be concluded that 92% of the samples analysed had mycotoxin levels below the Chinese regulatory limits. In terms of detection techniques in recent years, immuno-based assays have been developed largely due to their excellent sensitivity and ease of use. Assays targeting multiple mycotoxins like aflatoxins, ochratoxin A, zearalenone and deoxynivalenol have been reported using microarrays and suspension arrays targeting in particular maize, rice and peanuts. Aptamer-based assays against ochratoxin A and aflatoxins B1 and B2 have been developed involving fluorescence detection; and surface plasmon resonance immunosensors have been developed targeting wine, maize, wheat, wild rye, hay and peanut oil with high sensitivity (> 0.025 ng l(-1)). Commercialisation of these technologies is much needed for wider usage in the coming years.

Sample-pretreatment-free based high sensitive determination of aflatoxin M1in raw milk using a time-resolved fluorescent competitive immunochromatographic assay

A highly-sensitive TRFICA was developed to detect AFM₁in raw milk samples within 6 minutes without any sample pretreatments.

Enhanced spectrofluorimetric determination of aflatoxin M1 in liquid milk after magnetic solid phase extraction

A simple and sensitive method using magnetic solid phase extraction (MSPE) followed by spectrofluorimetric detection has been developed for separation and determination of aflatoxin M1 (AFM1) in liquid milk. The method is based on the extraction of AFM1 on the modified magnetic nanoparticles (MMNPs) and subsequent derivatization of extracted AFM1 to AFM1 hemi-acetal derivative (AFM2a) by reaction with trifluoroacetic acid (TFA) for spectrofluorimetric detection. Magnetic nanoparticles (MNPs) coated by 3-(trimethoxysilyl)-1-propantiol (TMSPT) and modified with 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) were used as adsorbent in MSPE procedure. Influential parameters affecting the extraction efficiency were investigated and optimized. Under the optimum conditions the calibration curve for AFM1 determination showed good linearity in the range 0.030-10.0 μg L(-1) (R(2) = 0.9991). The repeatability and reproducibility (RSD%) for 0.050 μg L(-1) of AFM1 were 4.5% and 5.3%, respectively and limit of detection limit (S/N = 3) was estimated to be 0.010 μg L(-1). The developed method was successfully applied for extraction of AFM1 from spiked liquid milk and natural contaminated liquid milk. The good spiked recoveries ranging from 91.6% to 96.1% were obtained. The results demonstrated that the developed method is simple, inexpensive, accurate and remarkably free from interference effects.

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.

Determination of aflatoxin M1 in liquid milk using high performance liquid chromatography with fluorescence detection after magnetic solid phase extraction

A new and sensitive method based on magnetic solid phase extraction (MSPE) with antibody-free modified magnetic nanoparticles (MMNPs) followed by high performance liquid chromatography with post-column derivatization and fluorescence detection (HPLC-PCD-FD) has been developed for the separation and determination of aflatoxin M₁ (AFM₁) in liquid milk.