Kinetic method for acetylsalicylic acid determination based on its inhibitory effect upon the catalytic decomposition of H2O2

The catalytic reaction of catalase was investigated, by means of a Clark oxygen sensor, in the presence of various concentrations of acetylsalicylic acid. Michaelis-Menten kinetic parameters were determined from Lineweaver-Burk plots, obtained in the absence and in the presence of the inhibitor. The inhibition pattern, suggested by the Lineweave-Burk plots, corresponds to a fully mixed inhibition mechanism. A kinetic method, based on the indicator reaction: H2O2 --> catalase, acetylsalicylic acid H2O + 0.5O(2), was developed for the quantitative determination of acetylsalicylic acid. Calibration graphs of the reciprocal value of first-order rate constant versus acetylsalicylic concentration covered the concentration range (2.99-19.98)x10(-4) mol/L, while the detection limit was 4.12x10(-4) mol/L acetylsalicylic acid with a standard deviation of 2.1x10(-5) mol/L.