Department of Chemistry, Shandong University, Jinan, P.R. China Manuscript received 23 December 1998, accepted 28 December 1998 In HAc-NaAc (1 : 1) buffer solution, FeIII-5-Br-PADAP-NO3 system sensitively presents a reductive wave at a banging mercury drop electrode (HMDE). The reductive wave is a catalytical adsorptive complex wave. In 0.05 mol dm-3 HAc-NaAc and 4.0 x 10-6 mol dm-3 5-Br-PADAP solution, the second derivative peak height of the reductive wave is linearly proportional to the concentration of FeIII in the range from 1.0 x 10-10 to 1.0 x 10-7 mol dm-3. The detection limit is 6.0 x 10-11 mol dm-3. The method has been applied to determine trace amount of iron samples of pig meat and tap water.