De Queiroz J.C.,Brazilian Radiological Protection and Dosimetry Institute (IRD) |
Ferreira A.C.D.M.,Brazilian Radiological Protection and Dosimetry Institute (IRD) |
Da Costa A.C.A.,Institute Qumica
The Scientific World Journal | Year: 2012
Toxicity of thorium by Monoraphidium sp. and Scenedesmus sp. was studied. Microalgal cultures were inoculated in ASM-1 medium in presence and absence of thorium. Its effect was monitored by direct counting on Fuchs-Rosenthal chamber and with software. The toxicity of thorium over the species was observed for concentrations over 50.0mg/L. After 30 days, Monoraphidium cells decreased their concentration from 4.23 10 6 to 4.27 10 5 and 8.57 10 5 cells/mL, in the presence of 50.0 and 100.0mg/L of thorium, respectively. Scenedesmus sp. cells were more resistant to thorium: for an initial cell concentration of 7.65 10 4 cells/mL it was observed a change to 5.25 10 5 and 5.12 10 5 cells/mL, in the presence of thorium at 50.0 and 100.0mg/L, respectively. This is an indication that low concentrations of the radionuclide favored the growth, and that Scenedesmus cells are more resistant to thorium than Monoraphidium cells. The software used for comparison with direct count method proved to be useful for the improvement of accuracy of the results obtained, a decrease in the uncertainty and allowed recording of the data. The presence of thorium suggests that low concentrations have a positive effect on the growth, due to the presence of the nitrate, indicating its potential for ecotoxicological studies. Copyright 2012 Juliana Cristina de Queiroz et al.
De Souza F.C.,Institute Qumica |
De Vasconcellos F.J.,Institute Qumica |
Cabral R.C.,Institute Qumica |
Fernandez T.L.,Institute Qumica |
D'Elia E.,Institute Qumica
CYTA - Journal of Food | Year: 2013
Two enzymatic methods using amperometric and colorimetric detection based on two coupled activities (glyceroquinase and glycerol-3-phosphate oxidase) were compared for the glycerol content determination. The enzymatic conversion of glycerol consumes oxygen, which is measured amperometrically in a Clark-type electrode and correlated with the glycerol concentration. In addition to the enzymatic-colorimetric method, there is a third enzymatic reaction that can be used to form a coloured compound; this method involves the addition of peroxidase, 4-chlorophenol and 4-aminoantipyrine. The enzymatic methods studied showed good linearity in the range of 4 to 60 mmol L71 glycerol with a detection limit of 1 mmol L71. Studies of glycerol recovery in fortified sugar cane liquor showed a recovery of 98 + 2% for the enzymatic-amperometric method and of 96 + 1% for the enzymatic-colorimetric method. These two methods were applied to the determination of glycerol in beverages and good correlations were found between these methods. © 2013 Taylor & Francis.