Evaluation of the bright greenish yellow fluorescence test as a screening technique for aflatoxin-contaminated maize in Malawi

The bright greenish yellow fluorescence (BGYF) test has been used with varying success in screening for aflatoxins in maize. This test was applied to 180 maize samples collected from different markets within 12 districts of Malawi in order to evaluate its performance against high performance liquid chromatographic analysis. The number of BGYF grains in 2.5 kg unground samples ranged from 0 to 35 and about 49% of all tested samples had aflatoxin concentrations ranging from 1 to 382 mu g/kg. A total of 65 (36%) of the examined unground samples showed no BGYF. The European Commission recommends a false negative rate of less than 5% for a screening technique to be acceptable. In this study, four BGYF grains per 2.5 kg unground maize sample successfully indicated an aflatoxin contamination of >10 mu g/kg (10 mu g/kg being the maxium tolerable level proposed by the Common Market for Eastern and Southern Africa), with a 4.4% false negative rate. In this case, the amount of confirmatory analyses would be reduced by 63%, if the BGYF test was employed as a screening method. The screening technique therefore offers a practical tool for Malawi and possibly for the Sub-Saharan region

A synchrotron radiation study of the hydrothermal synthesis of layered double hydroxides from MgO and Al2O3 slurries

The hydrothermal reaction of slurries containing MgO and Cp3 alumina has been investigated in situ using energy dispersive X-ray diffraction (EDXRD). A range of temperatures (100, 150, 180 and 240 °C) were studied. Kinetic data for the formation of the hydrotalcite-like Mg-Al layered double hydroxide (LDH) have been determined. At 100 °C the LDH is the predominant phase that is formed but at higher temperatures the impurity phases brucite and boehmite become more significant. The rate of reaction increases with temperature in agreement with Arrhenius behaviour and the LDH growth curves exhibit sigmoidal kinetics. The rate of formation of the LDH phase was found to be approximately equal to the rate of consumption of MgO, indicating that the mechanism of LDH formation is unlikely to proceed via a long-lasting intermediate phase. © The Royal Society of Chemistry 2007