Page 90 - Pharmaceutical Analytical Chemistry III

❑DETERMINATION :
Photometric method (DPD reagent)

Elemental chlorine, hypochlorous acid and hypochlorite ion

react with N,N-diethyl-1,4-phenylenediamine (DPD) to form a

red colored azo dye. This colored semiquinoid salt is stabilized

by mesomerism

C2H5 NH2 + +1/21C/2l2Cl2 C2H5 . + +
N N Cl-
NH2
C2H5 C2H5

+

C2H5 . NH2 Cl-

+

N

C2H5