A kinetic method for para-nitrophenol determination based on its inhibitory effect on the catalatic reaction of catalase

Abstract

The inhibitory effect of para-nitrophenol on the catalytic reaction of catalase was investigated. Michaelis-Menten kinetic parameters were determined from Lineweaver-Burk plots obtained in the absence or in the presence of the inhibitor. The inhibitor pattern, revealed by the Lineweaver-Burk plots, suggested a fully mixed inhibition mechanism. Spectrophotometric monitoring of the indicator reaction: H 2 O 2 catalase, para−nitrophenol − −−−−−−−−−−−−−−−− → H 2 O+ 1 2 O 2 in conjunction with initial rate measurements was employed for the kinetic determination of the inhibitor. Calibration plots of initial rate vs. para-nitrophenol concentration were linear in the concentration range 0.9·10 −5 -2.5·10 −5 mol/L and the detection limit was 3·10 −6 mol/L (417 µg/L) para-nitrophenol. Interferences from other phenolic compounds like orto-cresole, metaand orto-nitrophenol were observed.