Spectrophotometric determination of aminopropyrone in pharmaceutical preparations

Studies on analysis of mixed pharmaceutical preparations. IX

Abstract

Aminopropyrone (I) react with CuSO₄ and pyridine to give a light-green color (Cu complex) with λ_max absorption at 410 mμ.
A new spectrophotometric method for (I) based on this color reaction was established, and applied to the determination of (I) in pharmaceutical preparations.
The influences of 48 compounds on the determination were investigated, among which those by sulpyrine, N-methylaminoantipyrine, salicylates, theophylline, barbiturates, amino acids, ascorbic acid, sodium citrate etc. could be eliminated by chloroform extraction in an alkaline medium.
The recommended analytical procedure was as follows. Take the sample containing 50 mg of (I) in a separatory funnel. Add 20 ml of water and 10 ml of 0.1N NaOH, and extract 5 times with 30 ml portions of chloroform. Combine the chloroform extracts and evaporate on a water bath.
Dissolve the residue in 50 ml of water. Transfer the solution to a 100 ml volumetric flask, and make up to volume exactry with water.
Transfer a 5 ml aliquot into a 30 ml glass-stoppered test tube, and add 5 ml of 0.1% CuSO₄-pyridine solution. Add water to make up to 25 ml, and measure the absorbance at 410 mμ (E_T) against water.
At the same time, the absorbance of the standard solution (E_S) is determined and the amount of (I) is calculated by E_T /E_S.