ABSTRACT
An artificial neural network (ANN) calibration model was developed to determine aluminum in the presence of iron in soil extracts, using xylenol orange as chromogenic reagent. The spectral data of synthetic mixtures of Al(3+) and Fe(3+) as well as of the soil extracts, were recorded in the range between 410 and 580 nm. Method validation was carried out using 18 soil extracts. The results gave good linear correlations between the ANN model and the ICP OES measurements for both species.
ABSTRACT
The thermoxidative stability of partially hydrogenated soybean oil (PHSBO) was examined after addition of ferric stearate and ferrous octanoate, and then heating the samples at 120, 160, 180, and 200 degrees C. In a second experiment, the effect of iron concentration (ferric stearate) on PHSBO stability was examined at 180 degrees C, and at concentrations of approximately 0.5 and 1.2 mg of added iron/kg PHSBO. Oil samples were heated continuously for 72 h and sampled every 12 h. The acid value, p-anisidine value, color, dielectric constant and the triacylglycerol polymer content of oil samples were compared to oil samples containing no added iron. Generally, the value of each oxidative index increased with (1) an increase in temperature, (2) an increase in heating time, and/or (3) an increase in iron. The results demonstrate that low concentrations of iron will substantially increase the rate of oxidation for vegetable oil samples heated to temperatures of 120 degrees C to 200 degrees C.
