A polarographic catalytic wave of diphtheria antitoxin (DAT) in 0.1 M HAc-N
aAc (pH 3.9 +/- 0.1) buffer solution containing 1 x 10(-4) M KIO3 is report
ed. The catalytic wave of DAT has characteristics of a parallel wave. The p
eak current of the catalytic wave was linearly proportional to DAT concentr
ation in the range of 0.2-10IU/mL.