Define Principle of colorimetric method-2, 4 dinitrophenylhydrazine?
Ascorbic acid is oxidized to dehydro ascorbic acid by copper (Cu++) ions. 2, 4 dinitrophenyl hydrazine reacts with the ketone group of dehydro ascorbic acid under acidic conditions to give osazone. The depth of the yellowish orange coloured osazone produced upon acidification with sulphuric acid is directly proportional to the amount of ascorbic acid present and can be measured photometrically at 540 nm wavelength.
As you carry out the procedure in the laboratory you will understand the method even better. So then let's get started and practically learn the two methods we have studied above. There are four activities in this practical.