Azmat, R: Reduction of methylene blue with reducing sugars

The photobleaching of methylene blue with reducing
sugars in 50% aqueous methanol using acetate buffer
has been investigated with steady illumination of
monochromatic radiations of 661 nm on specially
designed optical bench in a dark room. The dye
reduction processes were studied at various
parameters i) concentrations of dye, ii)
concentrations of reductants such as Galactose,
D-Mannose, D-Ribose, Maltose and Lactose, iii)
acidity Ho of reaction solution iv) temperature as a
function of quantum yield . Hammett acidity
function Ho was used to determine acidity of the
reaction solution. The optical method was adopted to
evaluate the values of Ho.
Bleaching of the dye simultaneously with
demethylation has been observed upon irradiation,
color recover as the source of irradiation turned off
or exposure to air. Reaction follows second order
kinetics with respect to dye concentration and
reductant and first order with respect to triplet
transient species with life time of 10.1 micro s.