Simultaneous detection of type A and type B trichothecenes in cereals by liquid chromatography–electrospray ionization mass spectrometry using NaCl as cationization agent

Advanced hyphenated chromatographic-mass spectrometry in mycotoxin determination: current status and prospects

Mass spectrometric techniques are essential for advanced research in food safety and environmental monitoring. These fields are important for securing the health of humans and animals, and for ensuring environmental security. Mycotoxins, toxic secondary metabolites of filamentous fungi, are major contaminants of agricultural products, food and feed, biological samples, and the environment as a whole. Mycotoxins can cause cancers, nephritic and hepatic diseases, various hemorrhagic syndromes, and immune and neurological disorders. Mycotoxin-contaminated food and feed can provoke trade conflicts, resulting in massive economic losses. Risk assessment of mycotoxin contamination for humans and animals generally depends on clear identification and reliable quantitation in diversified matrices. Pioneering work on mycotoxin quantitation using mass spectrometry (MS) was performed in the early 1970s. Now, unambiguous confirmation and quantitation of mycotoxins can be readily achieved with a variety hyphenated techniques that combine chromatographic separation with MS, including liquid chromatography (LC) or gas chromatography (GC). With the advent of atmospheric pressure ionization, LC-MS has become a routine technique. Recently, the co-occurrence of multiple mycotoxins in the same sample has drawn an increasing amount of attention. Thus, modern analyses must be able to detect and quantitate multiple mycotoxins in a single run. Improvements in tandem MS techniques have been made to achieve this purpose. This review describes the advanced research that has been done regarding mycotoxin determination using hyphenated chromatographic-MS techniques, but is not a full-circle survey of all the literature published on this topic. The present work provides an overview of the various hyphenated chromatographic-MS-based strategies that have been applied to mycotoxin analysis, with a focus on recent developments. The use of chromatographic-MS to measure levels of mycotoxins, including aflatoxins, ochratoxins, patulin, trichothecenes, zearalenone, and fumonisins, is discussed in detail. Both free and masked mycotoxins are included in this review due to different methods of sample preparation. Techniques are described in terms of sample preparation, internal standards, LC/ultra performance LC (UPLC) optimization, and applications and survey. Several future hyphenated MS techniques are discussed as well, including multidimensional chromatography-MS, capillary electrophoresis-MS, and surface plasmon resonance array-MS.

Natural occurrence of type-B trichothecene mycotoxins in Korean cereal-based products

Type-B trichothecenes (deoxynivalenol (DON), nivalenol (NIV), fusarenone-X (FUS-X), 15-acetyldeoxynivalenol (15ADON), and 3-acetyldeoxynivalenol (3ADON)) were determined in 338 cereal-based products. Detection limit, quantification limit and mean recovery for five toxins were in the ranges 0.7-2.6 µg kg(-1), 2.1-7.8 µg kg(-1) and 73-110%, respectively. The range of occurrence and average level in samples were, respectively, 21-88% and 5.2-121.8 µg kg(-1) for NIV, 10-96% and 1.7-109.5 µg kg(-1) for DON, 2-39% and 0.4-3.6 µg kg(-1) for FUS-X, 0-80% and 0-17.3 µg kg(-1) for 15ADON, and 0-29% and 0-1.5 µg kg(-1) for 3ADON. Regarding co-occurrence, 64% of samples had more than two type-B trichothecenes. The estimated daily intakes of NIV, DON, FUS-X, 15ADON, and 3ADON were 0.077, 0.048, 0.004, 0.006 and 0.002 µg kg(-1) bw day(-1), respectively. These results suggest that current exposure levels do not indicate the possibility of adverse effects, but consideration of the combined exposure of type-B trichothecenes may be required due to the high frequency of co-occurrence.

Determination of Fusarium mycotoxins by liquid chromatography/tandem mass spectrometry coupled with immunoaffinity extraction

A method for the simultaneous quantitative determination of deoxynivalenol (DON), T-2 toxin (T-2), HT-2 toxin (HT-2) and zearalenone (ZEN) in wheat and biscuit by liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) coupled with immunoaffinity extraction is described. A clean-up was carried out using a DZT MS-PREP immunoaffinity column (IAC), and the effect of the sample dilution rate and sample loading was investigated. Furthermore, the effects of ion suppression of a multifunctional column (MFC) and the IAC in the clean-up were compared. The results with the DZT MS-PREP IAC showed that it is possible to make the sample dilution rate low, and indicated a higher solvent-tolerance than usual with an IAC. Sample loading was optimized at 0.25 g. Ion suppression was lowered by purification of the toxins using the DZT MS-PREP IAC. Recoveries of each mycotoxin from wheat and biscuit samples spiked at two levels ranged from 78 to 109%. The limits of detection in wheat and biscuit was in the range of 0.03-0.33 ng x g(-1). From these studies, it is suggested that use of an IAC is effective in the clean-up of each mycotoxin, and, when combined with LC/ESI-MS/MS, it is good for the determination of mycotoxins in foodstuffs due to its rapidity and high sensitivity.

T-2 toxin adsorption by hectorite

The adsorption of T-2 toxin by the natural smectite mineral-hectorite at pH 3.0, 7.0 and 9.0 was investigated. The results of T-2 toxin adsorption on hectorite showed that the T-2 adsorption capacity decreased with increasing concentration of adsorbent in the suspension for all the investigated pH values. From the adsorption isotherms, an increase in T-2 toxin adsorption with increasing initial T-2 toxin concentration was observed for all the investigated pH values. The T-2 toxin adsorption by hectorite followed a non-linear (Langmuir) type of isotherm at pH 3.0, 7.0 and 9.0, with correlation coefficients (r2) of 0.943 at pH 3.0, 0.919 at pH 7.0 and 0.939 at pH 9.0. The estimated maximum T-2 toxin adsorption by hectorite based on the Langmuir fit to the data (9.178 mg/g at pH 3.0, 9.930 mg/g at pH 7.0, and 19.341 mg/g at pH 9.0), indicated that the adsorption of T-2 toxin by hectorite is pH dependent. The obtained data suggest the existence of specific active sites in hectorite onto which the T-2 toxin is adsorbed.

Determination of trichothecenes in cereals and cereal-based products by liquid chromatography–tandem mass spectrometry

A sensitive, accurate and precise method for the simultaneous determination of nivalenol (NIV), deoxynivalenol (DON), T-2 toxin (T-2) and HT-2 toxin (HT-2) in different food matrices, including wheat, maize, barley, cereal-based infant foods, snacks, biscuits and wafers, has been developed. The method, using liquid chromatography coupled with atmospheric pressure chemical ionization triple quadrupole mass spectrometry (LC-APCI-MS/MS), allowed unambiguous identification of the selected trichothecenes at low microg per kg levels in such complex food matrices. A clean-up procedure, based on reversed phase SPE Oasis HLB columns, was used, allowing good recoveries for all studied trichothecenes. In particular, NIV recoveries significantly improved compared to those obtained by using Mycosep #227 columns for clean-up of the extracts. Limits of detection in the various investigated matrices ranged 2.5-4.0 microg kg(-1) for NIV, 2.8-5.3 microg kg(-1) for DON, 0.4-1.7 microg kg(-1) for HT-2 and 0.4-1.0 microg kg(-1) for T-2. Mean recovery values, obtained from cereals and cereal products spiked with NIV, DON, HT-2 and T-2 toxins at levels from 10 to 1000 microg kg(-1), ranged from 72 to 110% with mean relative standard deviation lower than 10%. A systematic investigation of matrix effects in different cereals and cereal products was also carried out by statistically comparing the slopes of standard calibration curve with matrix-matched calibration curve for each of the four toxins and the eight matrices tested. For seven of the eight matrices tested, statistically significant matrix effects were observed, indicating that, for accurate quantitative analysis, matrix-matched calibration was necessary. The method was applied to the analysis of 57 samples of ground wheat originated from South Italy and nine cereal food samples collected from retail markets.

Adsorption of T-2 toxin by natural mineral adsorbents

The contamination of animal feed with mycotoxins represents a worldwide problem leading to economic losses in animal production. According to the Food and Agriculture Organization (FAO), 25% of the world's cereal grain production is contaminated with mycotoxins. The most common mycotoxins found in grains are the aflatoxins, ochratoxins, fumonisins, trichothecenes, zearalenone and the ergopeptine alkaloids. Trichothecenes, constitute the largest group of Fusarium mycotoxins. Among others, T-2 toxin is the most acute toxic trichothecene. In this paper, adsorption of T-2 toxin by natural mineral adsorbents zeolite-clinop-tilolite and smectite minerals - bentonite and hectorite, at pH 3 was investigated. The highest adsorption index was achieved for hectorite (95%), while clinoptilolite and bentonite showed low adsorption index for T-2 toxin, 8% and 13%, respectively. Results of T-2 toxin adsorption on hectorite, at different amount of solid phase in suspension, and at pH 3, 7 and 9, showed that toxin adsorption indexes increased with increase of adsorbent concentration in suspension, at all investigated pH values. No significant differences in T-2 toxin adsorption by hectorite, at pH 3, 7 and 9 were observed.

Trace mycotoxin analysis in complex biological and food matrices by liquid chromatography–atmospheric pressure ionisation mass spectrometry

Mycotoxins are toxic secondary metabolites produced by filamentous fungi that are growing on agricultural commodities. Their frequent presence in food and their severe toxic, carcinogenic and estrogenic properties have been recognised as potential threat to human health. A reliable risk assessment of mycotoxin contamination for humans and animals relies basically on their unambiguous identification and accurate quantification in food and feedstuff. While most screening methods for mycotoxins are based on immunoassays, unambiguous analyte confirmation can be easily achieved with mass spectrometric methods, like gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS). Due to the introduction of atmospheric pressure ionisation (API) techniques in the late 80s, LC/MS has become a routine technique also in food analysis, overcoming the traditional drawbacks of GC/MS regarding volatility and thermal stability. During the last few years, this technical and instrumental progress had also an increasing impact on the expanding field of mycotoxin analysis. The aim of the present review is to give an overview on the application of LC-(API)MS in the analysis of frequently occurring and highly toxic mycotoxins, such as trichothecenes, ochratoxins, zearalenone, fumonisins, aflatoxins, enniatins, moniliformin and several other mycotoxins. This includes also the investigation of some of their metabolites and degradation products. Suitable sample pre-treatment procedures, their applicability for high sample through-put and their influence on matrix effects will be discussed. The review covers literature published until July 2006.

Characterization and application of isotope-substituted (13C15)-deoxynivalenol (DON) as an internal standard for the determination of DON

The powerful combination of liquid chromatography and mass spectrometry (MS) is often limited by matrix effects during ionization in the MS ion source. The use of fully isotope-substituted (13C15)-deoxynivalenol ((13C15)-DON) as an internal standard (IS) corrects matrix effects and improves the accuracy of analytical methods using mass spectrometry for the quantitative determination of the Fusarium mycotoxin deoxynivalenol (DON). The IS was characterized with respect to its chromatographic purity by liquid chromatography-ultraviolet light and its isotope distribution by time-of-flight mass spectrometry. Its low-energy collision-induced dissociation behaviour was compared with DON. Moreover, this work describes the successful application of (13C15)-DON as IS for the determination of DON in maize using high-performance liquid chromatography (HPLC) electrospray (ESI) with tandem mass spectrometry. The results demonstrate that the IS can successfully correct for fluctuations during extraction and clean-up of the sample as well as the ionization of DON in the MS ion source. Random variations in ionization affect the IS in the same way as the analyte. Recoveries for DON in maize of 76% +/- 1.9% (external calibration) or 101% +/- 2.4% (internal calibration) were reached, respectively, after sample clean-up.

A new solid phase extraction clean-up method for the determination of 12 type A and B trichothecenes in cereals and cereal-based food by LC-MS/MS

A new reliable and cost-efficient solid phase extraction-based clean-up method for the determination of 12 type A and B trichothecenes [deoxynivalenol (DON), nivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, fusarenon-X, T-2 toxin, HT-2 toxin, neosolaniol, monoacetoxy-scirpenol, diacetoxyscirpenol, T-2 triol and T-2 tetraol] in cereals and cereal-based food is presented. Furthermore, the suitability for the simultaneous determination of zearalenone is examined. Toxins were extracted from cereal samples using ACN/water (80/20, v/v), purified by means of a new Bond Elut Mycotoxin column and analyzed via liquid chromatography-electrospray ionization tandem mass spectrometry. Limits of detection were calculated for the matrix wheat and ranged from 0.3 to 5 ng/g, depending on the toxin. Average recovery rates for the tested compounds in seven cereal-based matrices have been determined ranging from 65 to 104%. The relative standard deviations of the complete method ranged from 2.67 (DON, wheat) to 20.0% (T-2 toxin, oats).

Recent advances in mycotoxin determination in food and feed by hyphenated chromatographic techniques/mass spectrometry

Mycotoxins are fungal toxins produced by molds, which occur universally in food and feed derivatives, and are produced under certain environmental conditions in the field before harvest, post-harvest, during storage, processing, and feeding. Mycotoxin contamination is one of the most relevant and worrisome problem concerning food and feed safety because it can cause a variety of toxic acute and chronic effects in human and animals. In this review we report the use of mass spectrometry in connection with chromatographic techniques for mycotoxin determination by considering separately the most diffuse class of mycotoxins: patulin, aflatoxins, ochratoxin A, zearalenone, trichothecenes, and fumonisins. Although the selectivity of mass spectrometry is unchallenged if compared to common GC and LC detection methods, accuracy, precision, and sensitivity may be extremely variable concerning the different mycotoxins, matrices, and instruments. The sensitivity issue may be a real problem in the case of LC/MS, where the response can be very different for the different ionization techniques (ESI, APCI, APPI). Therefore, when other detection methods (such as fluorescence or UV absorbance) can be used for the quantitative determination, LC/MS appears to be only an outstanding confirmatory technique. In contrast, when the toxins are not volatile and do not bear suitable chromophores or fluorophores, LC/MS appears to be the unique method to perform quantitative and qualitative analyses without requiring any derivatization procedure. The problem of exact quantitative determination in GC/MS and LC/MS methods is particularly important for mycotoxin determination in food, given the high variability of the matrices, and can be solved only by the use of isotopically labeled internal standards or by the use of ionization interfaces able to lower matrix effects and ion suppressions. When the problems linked to inconstant ionization and matrix effects will be solved, only MS detectors will allow to simplify more and more the sample preparation procedures and to avoid clean-up procedures, making feasible low-cost, high-throughput determination of mycotoxins in many different food matrices.

Suitability of a fully 13C isotope labeled internal standard for the determination of the mycotoxin deoxynivalenol by LC-MS/MS without clean up

Very often, the accuracy of quantitative analytical methods for the determination of mycotoxins by liquid chromatography (LC)-mass spectrometry (MS) and LC-MS/MS is limited by matrix effects during the ionization process in the MS source. Stable isotope labeled standards are best suited to correct for matrix effects and to improve both the trueness and the precision of analytical methods employing LC-MS and LC-MS/MS. This paper describes the successful use of fully 13C isotope labeled deoxynivalenol [(13C15)DON] as an internal standard (IS) for the accurate determination of DON in maize and wheat by LC electrospray ionization MS/MS. To show the full potential of (13C15)DON as IS, maize and wheat extracts were analyzed without further cleanup. Subsequent to calibration for the LC-MS end determination, DON was quantified in matrix reference materials (wheat and maize). Without consideration of the IS, apparent recoveries of DON were 29+/-6% (n=7) for wheat and 37+/-5% (n=7) for maize. However, the determination of DON in the reference materials yielded 95+/-3% (wheat) and 99+/-3% (maize) when (13C15)DON was used as an IS for data evaluation.

An innovative LC/MS approach applied to the determination of zeralenone in maize: Alternate Isotope-coded Derivatization Assay (AIDA)

Zearalenone is a mycotoxin mainly produced by severalFusarium species, which are known to colonize grains in temperate climates. The purpose of the study is to provide a reliable isotope dilution method for the quantification of this mycotoxin. A derivative of the analyte to be used as standard is obtained by reaction with acetic anhydride, which is available in two pure isotopic forms, a protonated ("light") and a hexadeuterated ("heavy"). The derivatized standards are added to the matrix split intwo parts. Then, the derivatization procedure is repeated on both matrices derivatizing the part containing the "heavy" labelled standard with the "light" acetic anhydride and the part containing the "light" labelled standard with the "heavy" acetic anhydride. Both extracted mixtures are analyzed by LC/MS, monitoring the "light" and the "heavy" labelled analytes and using the former as standard for the latter in one case and viceversa in the other case. The method allowed to obtain very good results, without the need of IAC purification.

A rapid multiresidual determination of type A and type B trichothecenes in wheat flour by HPLC-ESI-MS

A new, rapid and sensitive method is reported for the multiresidual determination of type A (diacetoxyscirpenol, HT-2 toxin, T-2 toxin) and type B (nivalenol, deoxynivalenol, fusarenon X, 15-O-acetyl-4-deoxynivalenol) trichothecenes in wheat flour samples. Sample extraction was performed with acetonitrile/water mixtures. Mycosep columns were used for a fast and effective clean-up procedure. The analytes were separated by HPLC with a RP C18 column by means of a gradient elution and detected in an ESI-interfaced single quadrupole mass spectrometer. Type B and type A trichothecenes were monitored in the negative and in the positive ion mode, respectively. The method performance is reported in terms of linearity (r2 = 0.999), specificity, accuracy (recoveries from 70-120%) and precision (CV% = 5), the LOQs are in the range 10-20 microg/Kg.

Development of a multiresidue method for analysis of major Fusarium mycotoxins in corn meal using liquid chromatography/tandem mass spectrometry

A sensitive and reliable liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method has been developed to determine, in a single run, eight trichothecenes, three fumonisins, zearalenone and alpha-zearalenol, in corn meal samples. LC and MS conditions were varied to find the best compromise in terms of sensitivity and separation. An acceptable compromise was obtained using a C18 column thermostatted at 45 degrees C and a mobile phase gradient of methanol/water with 10 mmol/L formate buffer (pH 3.8). A multiple reaction monitoring program, in which fumonisins and trichothecenes (except nivalenol and deoxynivalenol) are acquired in positive ESI as [M+H]+ or [M+NH4]+, and all other compounds in negative ESI, was developed to match appropriate retention time windows. Sample preparation used a simple homogenization of the corn meal sample with acetonitrile/water (75:25, v/v) followed by extraction on a C18 cartridge and clean-up on a cartridge containing graphitized carbon black. Method detection limits were in the range 2-14 ng/g, with the exception of nivalenol (27 ng/g), deoxynivalenol (40 ng/g) and 15-acetyldeoxynivalenol (30 ng/g). Good accuracy (recoveries 81-104%) and precision (RSD 4-11%) were obtained by performing calibration using a spiked analyte-free extract.