Abstract:

An organic phase chitosan-ferrocene horseradish peroxidase multiwalled carbon nanotubes (CS-FC/HRP/
MWCNTs) enzyme sensor for the determination of peroxide value of vegetable oils was studied. The catalytic effect of
CS-FC/HRP/MWCNTs enzyme sensor on the electrochemical reduction of lipid hydroperoxide in organic phase was
investigated by cyclic voltammetry. The mechanism of the redox process of lauroyl peroxide and HRP was expounded.
The electrode process of CS-FC/HRP/MWCNTs enzyme-based sensor was typically controlled by the electrochemical
reaction on the electrode surface, instead of the diffusion of HRP protein. The micro-grid structure in three dimensions
which facilitated electrocatalytic reaction of enzyme sensor was observed by scanning electron microscopy technique (SEM).
The increase in catalytic reduction current of lauroyl peroxide at the CS-FC/HRP/MWCNTs enzyme sensor was linearly
correlated with substrate concentration in the range of 2.5 × 10-6 －3.0 × 10-5 mol/L (y = 0.108 5x – 0.354 8, R2 = 0.992 3).
Meanwhile, the limit of detection of this enzyme sensor was 2.0 × 10-7 mol/L (RSN = 3). The developed method was applied
to the determination of peroxide value of soybean oil and grapeseed oil, and the results well agreed with those obtained by
the classical iodometric titration method. Being more precise and accurate than iodometric titration method, it is a practical
method for rapid determination of peroxide value in vegetable oils.

Key words: organic phase enzyme sensor, multi-walled carbon nanotube, vegetable oil, determination of peroxide value