Table 3

First order kinetic rate constants fitted for the degradation experiments in reaction medium 1 with acetonitrile added as monitored by HPLC-UV

k(h−1)Buffer/MeCN Ratio
100:0 v/v90:10 v/v80:20 v/v70:30 v/v60:40 v/v50:50 v/v
β1-D0.0260.0210.0150.0120.0070.005
β1–20.180.140.100.0720.0470.032
Ratio am/h6.96.56.96.26.46.1

The dependence of the first order degradation rate constantskβ1-D (hydrolysis) andkβ1–2 (acyl migration) ofS-naproxen-β-1-O-acyl glucuronide in mixtures of 25 mM potassium phosphate buffer, pH 7.40, and increasing amounts of acetonitrile. Ratio am/h is the ratio between acyl migration (kβ1–2) and hydrolysis (kβ1-D) for S-nap-g. All nine first order rate constants in the equilibrium (data not shown) are slowed down by increasing amounts of acetonitrile.