A unique gold(111) oriented nanoparticles trapped carbon nanofiber-chitosan modified electrocatalyst coated glassy carbon electrode(GCE/CNF-CHIT@Au-nano) was prepared by an in-situ electrochemical procedure for efficient bifunctional electrocatalytic oxidation and reduction of formaldehyde and hydrogen peroxide in neutral pH solution. In the typical preparation, a microliter quantity of Au3+ solution was drop-casted on GCE/CNF-CHIT surface and potential cycled in pH 7 PBS. The GCE/CNFCHIT@Au-nano showed well-defined electrochemical response of gold nanoparticles of calculated electrochemically active surface area, 0.1347 cm(2), which is about 3-3000 times higher than that of the surface area of the respective unmodified electrodes such as polycrystalline Au (0.0407 cm(2)), GCE/CNF@Au-nano (0.0034 cm(2)) and GCE@Au-nano (0.0005 cm(2)). Physicochemical characterizations such as FESEM, EDAX, TEM, XRD, Raman, FTIR and XPS spectroscopic techniques revealed stabilization of 10 +/- 5 nm sized Au(111) phase oriented nanoparticles by the amino functional group of chitosan in the composite matrix. The detailed electrochemical characterization by cyclic voltammetry(CV), rotating disk electrode (RDE) and in-situ CV-electrochemical quartz crystal microbalance (EQCM; M-w = 44 +/- 1 g mol(-1) species was identified) techniques showed direct oxidation of formaldehyde to formate as an intermediate (45 g mol(-1)) without any CO poisoning, unlike the conventional Pt and Au based electrodes. Using a bipotentiostat, selective and simultaneous flow injection analyses of formaldehyde and hydrogen peroxide in a mixture at discreet applied potentials (E-app = 0.5 V/0.15 V and -0.15 V vs Ag/AgCl) were demonstrated. The applicability of the GCE/CNF-CHIT@Au-nano was tested by detecting formaldehyde and hydrogen peroxide in a commercial hair dye formulation with about 100% recovery values. (C) 2017 Elsevier Ltd. All rights reserved.