A novel magnetic graphene oxide modified with chitosan (MGO-CTS) was synthesised as an adsorbent aimed to examine the simultaneous removal of mycotoxins. The composite was characterised by various procedures, namely Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and a scanning electron microscope (SEM). The adsorption evaluation was considered via pH effects, initial mycotoxin concentration, adsorption time and temperature. Adsorption isotherm data and kinetics experiments were acquired at the optimum pH 5 fit Freundlich isotherm as well as pseudo-second-order kinetic models. The thermodynamic results indicated that the adsorption of the mycotoxins was spontaneous, endothermic and favourable.
A simple method for the reduction of aflatoxins B₁ (AFB₁), B₂ (AFB₂), G₁ (AFG₁), G₂ (AFG₂) and ochratoxin A (OTA) in white pepper was studied. Response surface methodology (RSM) was applied to determine the effect of four variables, which included time (20-60 min), temperature (30-70°C), calcium hydroxide (Ca(OH)₂) (0-1%) and hydrogen peroxide (H₂O₂) (1-3%) during the washing step of white pepper. The efficacy of the method was evaluated by the determination of mycotoxins by HPLC with fluorescence detection (FD). Statistical analysis showed that the experimental data could be adequately fitted into a second-order polynomial model, with a multiple regression coefficient (R²) in the range of 0.805-0.907 for AFG₂ and AFG₁, respectively. The optimal condition was 57.8 min, 62.0°C, of 0.6% (w/v) and 2.8% (v/v) for time, temperature, Ca(OH)₂ and H₂O₂ respectively. By applying the optimum condition, the mycotoxins reduction was found to be in the range of 68.5-100% for AFB₂ and AFG₁ respectively.
A new method for the simultaneous quantification of 12 mycotoxins was developed and optimized using reverse phase high performance liquid chromatography (RP-HPLC) with a photodiode array (PDA) and fluorescence detector (FLD), a photochemical reactor for enhanced detection (PHRED) and post-column derivatization. The mycotoxins included aflatoxins (AFB(1), AFB(2), AFG(1), and AFG(2)), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), fumonisins (FB(1), FB(2), and FB(3)), T-2 and HT-2 toxins. A double sample extraction with a phosphate-buffered saline solution (PBS) and methanol was used for co-extraction of mycotoxins, and a multifunctional immunoaffinity column was used for cleanup. Optimum conditions for separation of the mycotoxins were obtained to separate 12 mycotoxins in FLD and PDA chromatograms with a high resolution. The method gave recoveries in the range 72-111% when applied to spiked corn samples. The limits of detection (LOD) were 0.025 ng/g for AFB(1) and AFG(1), 0.012 ng/g for AFB(2) and AFG(2), 0.2 ng/g for OTA, 1.5 ng/g for ZEA, 6.2 ng/g for FB(1), FB(3) and HT-2 toxin, 9.4 ng/g for FB(2) and T-2 toxin, and 18.7 ng/g for DON. In addition, the limits of quantification (LOQ) ranged from 0.04 ng/g for AFB(2) and AFG(2) to 62 ng/g for DON. The method was successfully applied to the determination of these mycotoxins in 45 cereal samples obtained from the Malaysian market. The results indicated that the method can be applied for the multi-mycotoxin determination of cereals.
An electrochemical aptasensor is described for determination of the phytohormone of zearalenone (ZEA). The gold electrode was modified with ZEA via covalent attachment using cysteamine-hydrochloride and 1,4-phenylene diisocyanate linker. A truncated ZEA aptamer with a dissociation constant of 13.4 ± 2.1 nM was used in an aptasensor. The electrochemical property was investigated using square wave voltammetry for monitoring the change in the electron transfer using the ferro/ferricyanide system as redox probe. Under optimal experimental conditions, the response was best measured at a potential of 0.20 V (vs. Ag/AgCl). The signals depended on the competitive mechanism between the immobilised ZEA and free ZEA for the aptamer binding site. The aptasensor works in the range 0.01 to 1000 ng·mL-1 ZEA concentration, with a detection limit of 0.017 ng·mL-1. High degree of cross-reactivity with the other analogues of ZEA was observed, whereas none towards other mycotoxins. The aptasensor was further applied for the determination of ZEA in the extract of maize grain and showed good recovery percentages between 87 and 110%. Graphical abstract Schematic representation of the electrochemical determination of zearalenone based on indirect competitive assay. Step a Immobilisation of ZEA on the surface of gold electrode via covalent attachment, b competition for the ZEA aptamer binding site between immobilised and free ZEA, and c current signal of the binding event based on SWV technique.
Palm kernel cake (PKC) is a useful source of protein and energy for livestock. Recently, it has been used as an ingredient in poultry feed. Mycotoxin contamination of PKC due to inappropriate handling during production and storage has increased public concern about economic losses and health risks for poultry and humans. This concern has accentuated the need for the evaluation of mycotoxins in PKC. Furthermore, a method for quantifying mycotoxins in PKC has so far not been established. The aims of this study were therefore (1) to develop a method for the simultaneous determination of mycotoxins in PKC and (2) to validate and verify the method. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using an electrospray ionisation interface (ESI) in both positive- and negative-ion modes was developed for the simultaneous determination of aflatoxins (AFB₁, AFB₂, AFG₁ and AFG₂), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), fumonisins (FB₁ and FB₂), T-2 and HT-2 toxin in PKC. An optimum method using a 0.2 ml min⁻¹ flow rate, 0.2% formic acid in aqueous phase, 10% organic phase at the beginning and 90% organic phase at the end of the gradient was achieved. The extraction of mycotoxins was performed using a solvent mixture of acetonitrile-water-formic acid (79:20:1, v/v) without further clean-up. The mean recoveries of mycotoxins in spiked PKC samples ranged from 81% to 112%. Limits of detection (LODs) and limits of quantification (LOQs) for mycotoxin standards and PKC samples ranged from 0.02 to 17.5 μg kg⁻¹ and from 0.06 to 58.0 μg kg⁻¹, respectively. Finally, the newly developed method was successfully applied to PKC samples. The results illustrated the fact that the method is efficient and accurate for the simultaneous multi-mycotoxin determination in PKC, which can be ideal for routine analysis.