Analysis for zearalenone and α-zearalenol in cereals and swine feed using accelerated solvent extraction and liquid chromatography with fluorescence detection

Fusarium mycotoxins: The major food contaminants

Mycotoxins, which are secondary metabolites produced by toxicogenic fungi, are natural food toxins that cause acute and chronic adverse reactions in humans and animals. The genus Fusarium is one of three major genera of mycotoxin-producing fungi. Trichothecenes, fumonisins, and zearalenone are the major Fusarium mycotoxins that occur worldwide. Fusarium mycotoxins have the potential to infiltrate the human food chain via contamination during crop production and food processing, eventually threatening human health. The occurrence and development of Fusarium mycotoxin contamination will change with climate change, especially with variations in temperature, precipitation, and carbon dioxide concentration. To address these challenges, researchers have built a series of effective models to forecast the occurrence of Fusarium mycotoxins and provide guidance for crop production. Fusarium mycotoxins frequently exist in food products at extremely low levels, thus necessitating the development of highly sensitive and reliable detection techniques. Numerous successful detection methods have been developed to meet the requirements of various situations, and an increasing number of methods are moving toward high-throughput features. Although Fusarium mycotoxins cannot be completely eliminated, numerous agronomic, chemical, physical, and biological methods can lower Fusarium mycotoxin contamination to safe levels during the preharvest and postharvest stages. These theoretical innovations and technological advances have the potential to facilitate the development of comprehensive strategies for effectively managing Fusarium mycotoxin contamination in the future.

Zearalenone (ZEN) in Livestock and Poultry: Dose, Toxicokinetics, Toxicity and Estrogenicity

One of the concerns when using grain ingredients in feed formulation for livestock and poultry diets is mycotoxin contamination. Aflatoxin, fumonisin, ochratoxin, trichothecene (deoxynivalenol, T-2 and HT-2) and zearalenone (ZEN) are mycotoxins that have been frequently reported in animal feed. ZEN, which has raised additional concern due to its estrogenic response in animals, is mainly produced by Fusarium graminearum (F. graminearum), F. culmorum, F. cerealis, F. equiseti, F. crookwellense and F. semitectums, and often co-occurs with deoxynivalenol in grains. The commonly elaborated derivatives of ZEN are α-zearalenol, β-zearalenol, zearalanone, α-zearalanol, and β-zearalanol. Other modified and masked forms of ZEN (including the extractable conjugated and non-extractable bound derivatives of ZEN) have also been quantified. In this review, common dose of ZEN in animal feed was summarized. The absorption rate, distribution (“carry-over”), major metabolites, toxicity and estrogenicity of ZEN related to poultry, swine and ruminants are discussed.

Rapid and sensitive detection of mycotoxins by advanced and emerging analytical methods: A review

Quantification of mycotoxins in foodstuffs is extremely difficult as a limited amount of toxins are known to be presented in the food samples. Mycotoxins are secondary toxic metabolites, made primarily by fungal species, contaminating feeds and foods. Due to the presence in globally used grains, it is an unpreventable problem that causes various acute and chronic impacts on human and animal health. Over the previous few years, however, progress has been made in mycotoxin analysis studies. Easier techniques of sample cleanup and advanced chromatographic approaches have been developed, primarily high-performance liquid chromatography. Few extremely sophisticated and adaptable tools such as high-resolution mass spectrometry and gas chromatography-tandem MS/MS have become more important. In addition, Immunoassay, Advanced quantitative techniques are now globally accepted for mycotoxin analysis. Thus, this review summarizes these traditional and highly advance methods and their characteristics for evaluating mycotoxins.

On-line extraction coupled to liquid chromatographic analysis of hydrophobic organic compounds from complex solid samples-Application to the analysis of UV filters in soils and sediments

This work investigates the applicability of on-line extraction (OLE) directly coupled to liquid chromatography (LC) for the dynamic extraction of hydrophobic organic compounds from complex solid samples. The method operates within the existing apparatus of the LC by replacing the valve loop with an extraction vessel comprised of an empty guard column loaded with the sample. In this manner, extraction is accomplished by the mobile phase as it flows through the extraction vessel under high pressure without the need for additional apparatus other than those comprising the LC system or additional sample pretreatment steps. The experimental parameters affecting the extraction efficiency of the method were investigated and discussed in relation to both the extraction performance and the chromatographic efficiency. The method was optimized and applied for the first time to the extraction of hydrophobic UV filters from spiked soil and sediment samples yielding recoveries between 59 and 117% and reproducibility from 4.8 to 14.3%, which are comparable to those reported from more advanced sample preparation methods.

Rapid determination of Alternaria mycotoxins in tomato samples by pressurised liquid extraction coupled to liquid chromatography with fluorescence detection

A sensitive and reliable method using pressurised liquid extraction (PLE) followed by molecularly imprinted solid phase extraction (MISPE) and high performance liquid chromatography with fluorescence detection (HPLC-FLD) has been developed for the analysis of alternariol (AOH) and alternariol monomethyl ether (AME) in tomato samples. Influence of several extraction parameters that affect PLE efficiency were evaluated for the simultaneous extraction of both mycotoxins in the selected samples. AOH and AME were optimally extracted using MeOH/water (25:75, v/v) at 70°C as solvent, a pressure of 1000 psi and a single extraction cycle. The resulting PLE extracts were pre-concentrated by molecularly imprinted solid phase extraction (MISPE) cartridges followed of analysis by HPLC with fluorescence detection (λ_exc = 258, λ_em = 440 nm). The proposed method was applied to the analysis of AOH and AME in fortified tomato samples (20-72 µg· kg-1) with recoveries of 84-97% (RSD < 8%, n = 6) for AOH and 67-91% (RSD < 13%, n = 6) for AME. The detection limit for AOH and AME were 7 and 15 µg· kg^-1, respectively. The ensuing PLE-MISPE-HPLC-FLD method was validated for the analysis of both mycotoxins in tomato samples in accordance with European Commission Decision 2002/657/EC.

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.

Validation of a UHPLC-MS/MS method for quantification of zearalenone, α-zearalenol, β-zearalenol, α-zearalanol, β-zearalanol and zearalanone in human urine

Humans can be exposed to mycotoxins through the diet. Evaluation of exposure levels to mycotoxins can be performed by direct determination in urine. The present work proposes a sensitive ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the determination of zearalenone (ZON) and its five metabolites (α-zearalenol [α-ZOL], β-zearalenol [β-ZOL], α-zearalanol [zeranol, α-ZAL], β-zearalanol [teranol, β-ZAL] and zearalanone [ZAN]) in human urine samples. The method involves the enzymatic hydrolysis of the samples, extraction of the analytes using liquid-liquid extraction (LLE) with ethyl acetate/formic acid (99:1 v/v) and a cleanup step using hexane, prior to their quantification by UHPLC-MS/MS, using an electrospray ionization (ESI) interface in the negative mode. Zearalenone-d6 (ZON-d6) was used as surrogate. The limits of detection and the limits of quantification ranged from 0.03 to 0.3ngmL(-1) and from 0.1 to 1.0ngmL(-1), respectively. The method was validated using matrix-matched calibration and a spike recovery assay. Recovery rates for spiked samples ranged from 96% to 104%, with relative standard deviations lower than 8.5%. This method was satisfactorily applied to 42 urine samples from Tunisian women for the determination of zearalenone and its five metabolites.

Analysis of zearalenone and α-zearalenol in 100 foods and medicinal plants determined by HPLC-FLD and positive confirmation by LC-MS-MS

BACKGROUND

Mycotoxins, which may contaminate many foods and medicinal plants, are poisonous to humans. A high-performance liquid chromatography with fluorescence detection (HPLC-FLD) method was successfully developed for analysing the contamination levels of zearalenone (ZON) and its metabolite α-zearalenol (α-ZOL) in 100 widely consumed foods and medicinal plants in China. Samples were extracted with methanol-water (80:20, v/v), and cleaned up by using an immunoaffinity column.

RESULTS

The limits of detection of this developed method for ZON and α-ZOL were 4 µg kg(-1) and 2.5 µg kg(-1) , respectively. Recoveries for the samples spiked with three levels (30, 60 and 300 µg kg(-1) for ZON and α-ZOL) ranged from 85.8% to 96.1% with relative standard deviation (RSD) of 2.6-7.1% for ZON, and from 89.9% to 98.7% with RSD of 1.9-9.2% for α-ZOL. Twelve (12%) of these tested samples were contaminated with ZON at levels ranging from 5.3 to 295.8 µg kg(-1). The most contaminated samples were Semen coicis, four of them in a concentration level exceeding 60 µg kg(-1) 'maximum level' (range 68.9-119.6 µg kg(-1)). Positive samples were further confirmed by liquid chromatography-tandem mass spectrometry.

CONCLUSION

The results suggest that it is necessary to control ZON contamination in medicinal plants, especially Semen coicis. This is a successful study on the analysis of ZON and α-ZOL in medicinal plants in China by HPLC-FLD. Immunoaffinity clean-up and HPLC-FLD proved to have broad applicability in the field of simultaneously detecting ZON and α-ZOL in foods and medicinal plants and other complicated matrices.

Application of accelerated solvent extraction to the investigation of saikosaponins from the roots of Bupleurum falcatum

Accelerated solvent extraction (ASE) was applied to the extraction of saikosaponin a, saikosaponin c and saikosaponin d from the roots of Bupleurum falcatum. Main extraction parameters such as the extraction solvents, extraction temperature and static extraction time were investigated and optimized. The optimized procedure employed 70% methanol as extraction solvent, 120 degrees C of extraction temperature, 10 min of static extraction time, 60% of flush volume and the extraction recoveries of the three compounds were near to 100% with one extraction cycle. The extracted samples were analyzed by HPLC with UV detector. The HPLC conditions were as follows: Hypersil ODS2 (4.6 mmx250 mm, 5 microm) column, acetonitrile and water as mobile phase, flow rate of 1.0 mL/min, UV detection wavelength of 204 nm and injection volume of 20 microL. Compared with the traditional methods including heat-reflux extraction and ultrasonic-assisted extraction, the proposed ASE method was more efficient and faster to be operated. The results indicated that ASE was an alternative method for extracting saikosaponins from the roots of B. falcatum.

Application of pressurized liquid extraction in the analysis of aflatoxins B(1), B(2), G(1) and G(2) in nuts

Aflatoxins (AFs) B(1), B(2), G(1) and G(2) were extracted from nuts by using pressurized liquid extraction (PLE) and the PLE extracts were analyzed using HPLC with fluorescence detection using photochemical post-column derivatization without further cleanup procedures. Several extraction parameters such as temperature (25, 40, 60 and 80 degrees C), pressure (500, 1000, 1500 and 2000 psi), solvent extraction mixture (acetone, acetonitrile, ethyl acetate and methanol), number of cycles (1 and 2), use of dispersing agents and cell size (5 and 11 mL) were investigated for their effects on the extraction performance. The results showed 60 degrees C, 1500 psi, acetonitrile, one cycle and a cell size of 5 mL as most favorable PLE operating conditions. The proposed analytical method provides LODs below the maximum levels established by European Union regulations and the recoveries of the four AFs were between 77 and 93% at spiking levels of 4, 2 and 0.5 microg/kg for AFB(1) and AFG(1) and 1, 0.5 and 0.13 microg/kg for AFB(2) and AFG(2). Validation was carried out using certified reference materials. PLE has been applied for the first time to the analysis of AFs in nuts and offers the possibility for fast simple and accurate quantitative determination of studied mycotoxins.

An overview of conventional and emerging analytical methods for the determination of mycotoxins

Mycotoxins are a group of compounds produced by various fungi and excreted into the matrices on which they grow, often food intended for human consumption or animal feed. The high toxicity and carcinogenicity of these compounds and their ability to cause various pathological conditions has led to widespread screening of foods and feeds potentially polluted with them. Maximum permissible levels in different matrices have also been established for some toxins. As these are quite low, analytical methods for determination of mycotoxins have to be both sensitive and specific. In addition, an appropriate sample preparation and pre-concentration method is needed to isolate analytes from rather complicated samples. In this article, an overview of methods for analysis and sample preparation published in the last ten years is given for the most often encountered mycotoxins in different samples, mainly in food. Special emphasis is on liquid chromatography with fluorescence and mass spectrometric detection, while in the field of sample preparation various solid-phase extraction approaches are discussed. However, an overview of other analytical and sample preparation methods less often used is also given. Finally, different matrices where mycotoxins have to be determined are discussed with the emphasis on their specific characteristics important for the analysis (human food and beverages, animal feed, biological samples, environmental samples). Various issues important for accurate qualitative and quantitative analyses are critically discussed: sampling and choice of representative sample, sample preparation and possible bias associated with it, specificity of the analytical method and critical evaluation of results.

Mycotoxin analysis: an update

Mycotoxin contamination of cereals and related products used for feed can cause intoxication, especially in farm animals. Therefore, efficient analytical tools for the qualitative and quantitative analysis of toxic fungal metabolites in feed are required. Current methods usually include an extraction step, a clean-up step to reduce or eliminate unwanted co-extracted matrix components and a separation step with suitably specific detection ability. Quantitative methods of analysis for most mycotoxins use immunoaffinity clean-up with high-performance liquid chromatography (HPLC) separation in combination with UV and/or fluorescence detection. Screening of samples contaminated with mycotoxins is frequently performed by thin layer chromatography (TLC), which yields qualitative or semi-quantitative results. Nowadays, enzyme-linked immunosorbent assays (ELISA) are often used for rapid screening. A number of promising methods, such as fluorescence polarization immunoassays, dipsticks, and even newer methods such as biosensors and non-invasive techniques based on infrared spectroscopy, have shown great potential for mycotoxin analysis. Currently, there is a strong trend towards the use of multi-mycotoxin methods for the simultaneous analysis of several of the important Fusarium mycotoxins, which is best achieved by LC-MS/MS (liquid chromatography with tandem mass spectrometry). This review focuses on recent developments in the determination of mycotoxins with a special emphasis on LC-MS/MS and emerging rapid methods.

Supercritical fluid extraction of macrocyclic lactone mycotoxins in maize flour samples for rapid amperometric screening and alternative liquid chromatographic method for confirmation

A rapid and simple method for the direct screening of macrocyclic lactone mycotoxins (zearalenone, ZON; alpha-zearalenol, alpha-ZOL; and beta-zearalenol, beta-ZOL) in maize flour samples is proposed. The sample screening method comprises supercritical fluid extraction (SFE) and clean-up on Florisil adsorption cartridge of the selected toxic compounds, followed by continuous flow electrochemical detection. Those samples for which the total concentration is close to or above the threshold limit established by legislation (0.200 mg kg(-1)) are subjected to preconcentration on C18 chromatographic material and liquid chromatographic separation for confirmation purposes. This confirmation method allows the determination of ZON, alpha-ZOL and beta-ZOL in the range between 30 and 300 microg kg(-1), with a average relative standard deviation lower than 5.2 in all cases.

Use of compressed fluids for sample preparation: Food applications

This review attempts to provide an updated overview (including works published till June 2006) on the latest applications of compressed fluids as sample preparation techniques for food analysis. After a general review of the principles of supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE; also called accelerated solvent extraction, ASE or subcritical water extraction, SWE, when water is employed as extraction solvent), the principal applications of such techniques in the mentioned fields of food and natural products are described, discussing their main advantages and drawbacks.

Development of a new sample pretreatment procedure based on pressurized liquid extraction for the determination of fluoroquinolone residues in table eggs

A new method for the simultaneous determination of three fluoroquinolones (FQs) enrofloxacin (ENRO) ciprofloxacin (CIPRO) and sarafloxacin (SARA) in table eggs has been developed, applying pressurized liquid extraction (PLE) and liquid chromatography (LC) with fluorescence detection (LC-FLD). The influence of several extraction parameters (e.g. solvent mixture, temperature and extraction time) on FQs extraction efficiency and coextracted matrix interferents was evaluated using fortified control eggs and matrix matched standard curves. The results showed that FQs extraction efficiency depends mainly on solvent composition and the optimum extraction mixture was found to be phosphate 50mM, pH 3.0/acetonitrile (50:50, v/v). The optimized procedure employed 50% flush volume, 5min of static time and three extraction cycles at 70 degrees C and 1500psi. Method validation was performed according to the guidelines of the Directive 96/23/EC, using control egg samples, fortified with the target FQs in the range 50-1000ngg(-1) and applying the optimized extraction conditions on three different days, providing recoveries between 67-90% with RSDs lower than 11% in all cases. The decision limit (CCalpha) and detection capability (CCbeta) of the analytical method were found to be within the range 17-24ngg(-1) and 30-41ngg(-1), respectively. The method was successfully applied to the determination of ENRO and its metabolite CIPRO in incurred egg samples from ENRO-treated hens and LC-MS has been used and for confirmatory purposes.

Molecularly imprinted polymers applied to the clean-up of zearalenone and α-zearalenol from cereal and swine feed sample extracts

A molecularly imprinted polymer prepared using 1-allylpiperazine (1-ALPP) as the functional monomer, trimethyltrimethacrylate (TRIM) as the crosslinker and the zearalenone (ZON)-mimicking template cyclododecanyl-2,4-dihydroxybenzoate (CDHB) has been applied to the clean-up and preconcentration of this mycotoxin (zearalenone) and a related metabolite, alpha-zearalenol (alpha-ZOL), from cereal and swine feed sample extracts. The extraction of ZON and alpha-ZOL from the food samples was accomplished using pressurized liquid extraction (PLE) with MeOH/ACN (50:50, v/v) as the extraction solvent, at 50 degrees C and 1500 psi. The extracted samples were cleaned up and preconcentrated through the MIP cartridge and analyzed using HPLC with fluorescence detection (lambda (exc)=271/ lambda (em)=452 nm). The stationary phase was a polar endcapped C18 column, and ACN/MeOH/water 10/55/35 (v/v/v, 15 mM ammonium acetate) at a flow rate of 1.0 mL min(-1) was used as the mobile phase. The method was applied to the analysis of ZON and alpha-ZOL in wheat, corn, barley, rye, rice and swine feed samples fortified with 50, 100 and 400 ng g(-1) of both mycotoxins, and it gave recoveries of between 85 and 97% (RSD 2.1-6.7%, n=3) and 87-97% (RSD 2.3-5.6%, n=3) for alpha-ZOL and ZON, respectively. The method was validated using a corn reference material for ZON.

Molecularly imprinted polymers with a streamlined mimic for zearalenone analysis

Molecularly imprinted polymers (MIPs) with selective recognition properties for zearalenone (ZON), an estrogenic mycotoxin, and structurally related compounds have been prepared using the non-covalent imprinting approach. A rationally designed ZON analogue, cyclododecyl 2,4-dihydroxybenzoate (CDHB), that exhibits resemblance to ZON in terms of size, shape and functionality has been synthesized and used as template for MIP preparation instead of the natural toxin. Several functional monomers have been evaluated to maximize the interactions with the template molecule during the polymerization process. The polymer material prepared with 1-allylpiperazine (1-ALPP) as functional monomer, trimethyl trimethacrylate (TRIM) as cross-linker and acetonitrile as porogen (in a 1:4:20 molar ratio) displayed superior binding capacities than any other of the MIPs tested. Selectivity of this material for ZON and structurally related and non-related compounds has been evaluated using it as stationary phase in liquid chromatography. Our results demonstrate that the imprinted polymer shows significant affinity in the porogenic solvent for the template mimic (CDHB) as well as for the ZON and other related target metabolites in food samples, dramatically improving the performance of previously reported MIPs for ZON recognition. Therefore, MIPs can be an excellent alternative for clean-up and preconcentration of the mycotoxin in contaminated food samples.

Extraction and analysis of ochratoxin A in bread using pressurised liquid extraction and liquid chromatography

A pressurised liquid extraction (PLE) method for the analysis of ochratoxin A (OTA) in bread samples is given. Parameters such as solvent, temperature, pressure and time were investigated thoroughly. The optimized PLE conditions were: methanol as extraction solvent, 80 degrees C, 2000 psi and a 5-min cycle. OTA was determined by liquid chromatography coupled with fluorescence detection and confirmed by methyl ester derivatization. Under these conditions OTA recovery is 92.3% with a RSD of 5%. Limits of detection and quantification were 0.02 and 0.06 microg/kg, respectively. The proposed method was applied to 20 bread samples, finding two positive samples with OTA levels below the maximum permitted levels by the European Union.

Pressurized liquid extraction in the analysis of food and biological samples

Originally, the use of the pressurized liquid extraction technique (PLE) was mainly focused on the extraction of environmental pollutants present in soil matrices, sediments, and sewage sludge. However, more recently the distinct advantages of this technique are being exploited in diverse areas, including biology, and the pharmaceutical and food industries. The aim of the present review is to explore recent analytical applications of this extraction technique (PLE) in the extraction of contaminant compounds and matrix components in food and biological samples, placing special emphasis on the strategies followed to obtain a rapid, selective, efficient and reliable extraction process.

Analysis of zearalenone in cereal and Swine feed samples using an automated flow-through immunosensor

The development of a sensitive flow-though immunosensor for the analysis of the mycotoxin zearalenone in cereal samples is described. The sensor was completely automated and was based on a direct competitive immunosorbent assay and fluorescence detection. The mycotoxin competes with a horseradish-peroxidase-labeled derivative for the binding sites of a rabbit polyclonal antibody. Control pore glass covalently bound to Prot A was used for the oriented immobilization of the antibody-antigen immunocomplexes. The immunosensor shows an IC(50) value of 0.087 ng mL(-1) (RSD = 2.8%, n = 6) and a dynamic range from 0.019 to 0.422 ng mL(-1). The limit of detection (90% of blank signal) of 0.007 ng mL(-1) (RSD = 3.9%, n = 3) is lower than previously published methods. Corn, wheat, and swine feed samples have been analyzed with the device after extraction of the analyte using accelerated solvent extraction (ASE). The immunosensor has been validated using a corn certificate reference material and HPLC with fluorescence detection.