A simple and rapid high performance liquid chromatographic with fluorescence detection method for the determination of the aflatoxin B1, B2, G1 and G2 in peanuts, rice and chilli was developed. The sample was extracted using acetonitrile:water (90:10, v/v%) and then purified by using ISOLUTE® multimode solid phase extraction. After the pre-column derivatisation, the analytes were separated within 3.7 min using Chromolith® performance RP-18e (100-4.6mm) monolithic column. To assess the possible effects of endogenous components in the food items, matrix-matched calibration was used for the quantification and validation. The recoveries of aflatoxins that were spiked into food samples were 86.38-104.5% and RSDs were <4.4%. The method was applied to the determination of aflatoxins in peanut (9), rice (5) and chilli (10) samples. Liquid chromatography-tandem mass spectrometry analysis using triple quadruple analyser and operated in the multiple reaction monitoring modes on the contaminated samples was performed for confirmation.
Exposure to aflatoxins in the adult Malaysian diet was estimated by analysing aflatoxins in 236 food composites prepared as "ready for consumption". Dietary exposure to aflatoxin B1 (AFB1) ranged from 24.3 to 34.00 ng/kg b.w./day (lower to upper bound), with peanuts being the main contributor. Estimated liver cancer risk from this exposure was 0.61-0.85 cancers/100,000 population/year, contributing 12.4%-17.3% of the liver cancer cases. Excluding AFB1 occurrence data higher than 15 µg/kg reduced exposure by 65%-91% to 2.27-11.99 ng/kg b.w./day, reducing the cancer risk to 0.06-0.30 cancers/100,000 population/year (contributing 1.2%-6.1% liver cancer cases). Reducing further the ML of AFB1 from 15 to 5 µg/kg yielded 3%-7% greater drop in the exposure to 0.47-10.26 ng/kg b.w./day with an estimated risk of 0.01-0.26 cancers/100,000 population/year (0.2%-5.1% liver cancer cases attributed to dietary AFB1). These findings indicate that current MLs are adequate in protecting Malaysians' health.
A reversed-phase HPLC optimization strategy is presented for investigating the separation and retention behavior of aflatoxin B1, B2, G1, G2, ochratoxin A and zearalenone, simultaneously. A fractional factorial design (FFD) was used to screen the significance effect of seven independent variables on chromatographic responses. The independent variables used were: (X1) column oven temperature (20-40°C), (X2) flow rate (0.8-1.2 ml/min), (X3) acid concentration in aqueous phase (0-2%), (X4) organic solvent percentage at the beginning (40-50%), and (X5) at the end (50-60%) of the gradient mobile phase, as well as (X6) ratio of methanol/acetonitrile at the beginning (1-4) and (X7) at the end (0-1) of gradient mobile phase. Responses of chromatographic analysis were resolution of mycotoxin peaks and HPLC run time. A central composite design (CCD) using response surface methodology (RSM) was then carried out for optimization of the most significant factors by multiple regression models for response variables. The proposed optimal method using 40°C oven temperature, 1 ml/min flow rate, 0.1% acetic acid concentration in aqueous phase, 41% organic phase (beginning), 60% organic phase (end), 1.92 ratio of methanol to acetonitrile (beginning) and 0.2 ratio (end) for X1-X7, respectively, showed good prediction ability between the experimental data and predictive values throughout the studied parameter space. Finally, the optimized method was validated by measuring the linearity, sensitivity, accuracy and precision parameters, and has been applied successfully to the analysis of spiked cereal samples.
Mycotoxins are the secondary toxic metabolites produced naturally by fungi. Analysis of mycotoxins is essential to minimize the consumption of contaminated food and feed. In this present work, an ultrasensitive electrochemical immunosensor for the detection of aflatoxin B₁ (AFB₁) was successfully developed based on an indirect competitive enzyme-linked immunosorbent assay (ELISA). Various parameters of ELISA, including antigen⁻antibody concentration, blocking agents, incubation time, temperature and pH of reagents, were first optimized in a 96-well microtiter plate to study the antigen⁻antibody interaction and optimize the optimum parameters of the assay. The optimized assay was transferred onto the multi-walled carbon nanotubes/chitosan/screen-printed carbon electrode (MWCNTs/CS/SPCE) by covalent attachment with the aid of 1-Ethyl-3-(3-dimetylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Competition occurred between aflatoxin B₁-bovine serum albumin (AFB₁⁻BSA) and free AFB₁ (in peanut sample and standard) for the binding site of a fixed amount of anti-AFB₁ antibody. Differential pulse voltammetry (DPV) analysis was used for the detection based on the reduction peak of TMB(ox). The developed immunosensor showed a linear range of 0.0001 to 10 ng/mL with detection limit of 0.3 pg/mL. AFB₁ analysis in spiked peanut samples resulted in recoveries between 80% and 127%. The precision of the developed immunosensor was evaluated by RSD values (n = 5) as 4.78% and 2.71% for reproducibility and repeatability, respectively.
Previous studies showed that the frequency of beta-catenin mutation was different in mice when induced by different chemicals. The aim of this study is to compare the expression of beta-catenin and p53 in hepatocellular carcinoma (HCC) from areas with exposure to high and low levels of aflatoxin B1 (AFB1).