Affinity Capillary Electrophoresis Studies on the Influence of Alcohols on the Interaction of β-Cyclodextrin with Non-Steroidal Anti-Inflammatory Drugs

Abstract

The influences of methanol, ethanol, 1-propanol and 1-butanol on the binding constants of β-cyclodextrin (β-CD) with non-steroidal anti-inflammatory drugs such as acemetacin, indometacin, cinmetacin, sulindac and diclofenac sodium and the separation of these drugs were studied by affinity capillary electrophoresis. No obvious effect was observable upon addition of methanol up to 6% (v/v) in the running buffer, while the addition of other alcohols at the concentration of 2% resulted in obvious decrease in the binding constants of β-CD with acemetacin, indometacin, cinmetacin and sulindac. With an increasing chain length of added alcohols, all of these changes increased. Upon additions of different alcohols in the running buffer the change of the binding constant of β-CD with diclofenac sodium was inconspicuous. Based on these results, the separation conditions for these drugs were optimized. The presence of 6% methanol in the running buffer containing 3 mM β-CD was helpful to the baseline separation of these drugs. The electrophorograms of these drugs in the presence of ethanol, 1-propanol and 1-butanol showed a worse separation due to the decrease in the binding constants. The methods for the separation of these drugs and the study on the binding constants possess the advantages of easy performance, high speed and low sample consumption.