Fig. 12. Graphs showing the steps in the calculation of the first-order degradation coefficient for the separate suction cups, exemplified with Cup 22. The total mass of solute recovered in a suction cup (a and b) was normalized with the total mass injected. The natural logarithm of the fraction of reactive solute in solution, ln[F(x,z)'], was related to the time value where 50% of the total mass had passed the suction cup (c). Plotting ln[F(x,z)'] against this time value gave a graph with just two points (d), and the slope of this regression line gave a estimate of the first-order degradation coefficient.