time of aprindine. None of the eight compounds tested interfered with the aprindine peak (Table I).
Duplicate injections of five 50-mg raw material samples, extracted by a single analyst, gave a standard deviation (SO) of 0.01 and a relative standard deviation [RSD = (SD X 100)/mean] of 1.48%. Duplicate injections of five capsule samples containing 25 mghapsule gave a relative standard deviation of 1.04%. The relative error calculated for this formulation was +0.2%. Duplicate injections of five solution samples (1 mg/ml) gave a relative standard deviation of 0.79%.
No extra peaks were observed in the chromatograms of the refluxed or heated samples. Table I1 summarizes the results of the various degradation studies. With the exception of samples irradiated with UV light, the data indicate that aprindine is stable to these artificial degradation conditions. Analysis of the UV-irradiated solution showed detectable extra peaks. These were identified on the basis of their retention times to be N-phenyl-2-indanamine (11) and N,N-diethyl-N'-phenyl-l,3-propanediamine (111).
The formation of I1 and I11 may be due to a UV light-catalyzed homolytic cleavage of the appropriate carbon-nitrogen bond. Compounds I1 and I11 were reported previously as metabolites of aprindine (1,4). None of the degraded solutions showed any interference with the assay of aprindine. Due to the light sensitivity of aprindine, ampul formulations must be protected from light. Natural shelflife stability data on raw material and capsule formulations for 2 years and on ampuls for 1 year indicate that the material is stable. REFERENCES