EFFECT OF METAL-IONS ON THE QUANTITATIVE-DETERMINATION OF HYDROXAMIC ACIDS

The hydrolysis of hydroxamic acids to hydroxylamine is an important fi rst step in the quantitative analysis of hydroxamate siderophores. The rate of this hydrolysis can be increased by the addition of ferric ir on and the metals Mn(II), Cu(II), Ni(II), Cd(II), Cr(III), and AI(III) . The maximum hydrolysis rate is obtained at iron to desferal ratios g reater than 40:1, Using these conditions, >75% hydrolysis of the sider ophores desferal, rhodotorulic acid, and schizokinen was obtained in 2 h at temperatures as low as 70 degrees C, These low temperatures make possible the direct analysis of hydroxamates in culture media contain ing high concentrations of carbohydrates, An example of this technique showing increased siderophore formation in low-iron cultures of Bacil lus megaterium upon exposure to aluminum is presented.