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Analysis of Binary Mixtures of Pharmaceutical Amines by the Acid Dye Technique

1971; Elsevier BV; Volume: 60; Issue: 2 Linguagem: Inglês

10.1002/jps.2600600229

1520-6017

Fumi Matsui, W.N. French,

Analytical Chemistry and Sensors

A general procedure using the acid dye technique is described for the direct analysis of certain binary mixtures of pharmaceutical amines without prior separation. Benzene (or benzene containing a small amount of isoamyl alcohol) is used to extract selectively the ion‐pair formed between the amine and an indicator dye from a suitably buffered aqueous phase. The less‐polar amine of the binary mixture is determined using bromcresol purple, while the total of both amines is determined with bromthymol blue. The amount of the more‐polar amine is calculated by difference. Specific combinations examined include diphenhydramine‐ephedrine, prochlorperazine‐amphetamine, promazine‐phenmetrazine, promethazine‐ephedrine, promethazine‐codeine, diphenhydraminecodeine, and diphenylpyraline‐codeine. Recoveries for simulated mixtures average 99.76%, with an average coefficient of variation of 0.85 for an individual determination. The method has some limitations in accuracy for binary mixtures containing a large proportion of the less‐polar amine. The scope of the technique is demonstrated by application to several commercially available dosage forms.