Determination of procaine and related local anesthetics. II. Collaborative study.
The ion-pairing chromatographic method reported previously for the isolation and spectrophotometric determination of the local anesthetics, alone and in combination, was studied collaboratively. Three solutions were assayed. One containing procaine as the single active component gave an average recovery of 99.8 plus or minus 1.7%. A mixture of procaine and tetracaine gave results of 99.3 plus or minus 1.6 and 98.9 plus or minus 8.82%, respectively. A third solution containing procaine and propoxycaine assayed 100.0 plus or minus 1.5 and 99.1 plus or minus 1.9%, respectively. It was shown that low results for tetracaine were due to loss during the final evaporative step. The method for samples containing tetracaine should be studied further. The other methods have been adopted as official first action.