New Liquid Membrane Electrode for Determination of Lidocaine in Local Anesthetic Formulations

A new lidocaine-responsive liquid membrane electrode based on the use of the lidocaine reineckate ion pair complex in nitrobenzene solvent has been developed. The electrode displays a linear response for 10-2-10-5M lidocaine over the pH range of 3-6.5. The response time varies from 35 s to 1 min depending on the lidocaine concentration. The life span of the electrode is at least 1 month. Excipients and diluents commonly used in local anesthetic formulations do not interfere. Determination of lidocaine in some pharmaceutical preparations gives results with an average recovery of 99% of the nominal values and a mean standard deviation of 1.7% which compare favorably with those obtained by the U.S. Pharmacopeia method.