Kinetics of drug decomposition. Part 50: Graphic method for calculation of zero-order rate constants of sequential reaction of indometacine photodegradation.

Calculation of partial zero-order rate constants for a sequential reaction was presented following indometacine photochemical degradation according to the equation A k1 leads to B k2 leads to C k3 leads to D. When zero-order rate constants k1 not equal to k2 not equal to k3 and absorptivity coefficients a not equal to b not equal to c not equal to d, then individuell zero-order rate constants can be obtained from simple equations: k1 = [A]0/tA, k2 = [A]0/tB, k3 = [A]0/tC, where [A]0 is the initial concentration of a substrate, and tA, tB, tC are the starting times of the steps of the sequential reaction, which can be read from the plots for a relationship A = f(t).