Spectrophotometric determination of sulfide based on peroxidase inhibition by detection of purpurogallin formation

This paper presents a new method for spectrophotometirc detection of sulfide applying fungal peroxidase immobilized on sodium alginate. The sensing scheme was based on decrease of the absorbance of the orange compound, purpurogallin produced from pyrogallol and H2O2 as substrates, due to the inhibition of peroxidase by sulfide. Absorbance of purpurogallin was detected at 420 nm by using a spectrophotometer. The proposed method could successfully detect the sulfide in the concentration range of 0.6–7.0 μM with a detection limit of 0.4 μM. The kinetic parameters of Michaelis–Menten with and without sulfide were also calculated. Possible inhibition mechanism of peroxidase by sulfide was deduced according to the variation of parameters and uncompetitive mechanism was observed with respect to hydrogen peroxide. The current method provides an easy to use method for sulfide detection in water samples.

► Sulfur was detected spectrophotometerically based on enzyme inhibition.
► Decrease in purpurogallin formation due to enzyme inhibition by sulfide was related to sulfide concentration.
► Fungal peroxidase obtained from Coprinus cinereus was used as enzyme.