Spectrophotometric Determination of Molybdenum in Grain with Extraction From Bi-aqueous Medium of Ethanol and Ammonium Sulfate

It was found that the sensitivity of the red colored complex of Mo(Ⅵ)-salicylfluorone (SAF) with its mole ratio of 1 to 2,formed in pH 3.0 acetate buffer medium containing ethanol and ammonium sulfate (called bi-aqueous medium) was enhanced as compared with the same chromogenic reaction carried out in unitary aqueous medium without the addition of ethanol.Upon extraction by shaking the reaction mixture for 2 min,the Mo(Ⅵ)-SAF complex was transferred into the upper ethanol phase,having its absorption maximum at 516 nm (spectral change of bathochromic shift of 2 nm as compared with the Mo(Ⅵ)-SAF complex in unitary aqueous medium).Value of apparent molar absorptivity found was 1.12×105L·mol-1·cm-1 in ethanol phase.Linear relationship between values of absorbance and mass concentration of Mo(Ⅵ) was kept in the range within 20 mg·L-1,with detection limit (3S/N) of the method of 0.06 mg·L-1.The proposed method was applied to the determination of Mo(Ⅵ) in grain samples,giving values of recovery in the range of 97.4%-100.1%.