Glassy carbon (GC) electrode was modified with phenyl layer using electrochemical reduction of benzenediazonium tetrafluoroborate. The phenyl layer on GC inhibits direct electron transfer of ferrocyanide but allows for facile electrode kinetics of hydroxymethylferrocene (HMF) in solution-phase. Based on this selective electrochemical discrimination of phenyl layer, a voltammetric signal enhancement for the detection of HMF was studied at phenyl-modified GC electrode in phosphate buffer (PH = 7.2) solution containing ferrocyanide as a sacrificial species. The current amplification ratio (R) was found to be linear to the ferrocyanide concentration ranging from 0. 1 to 10 mM. (c) 2005 Elsevier B.V. All rights reserved.