Spectrophotometric determination of aluminium in pharmaceutical preparations by azo dyes of 1,2,4-triazole series

Azodyes, derivatives of 1,2,4-triazole and pyrocatechine: 3-(3′,4′-dihydroxyphenylazo-1′)-1,2,4-triazole (TRIAP) and 3-(3′,4′-dihydroxyphenylazo-1′)-5-mercapto-1,2,4-triazole (METRIAP), were used for spectrophotometric determination of Al. in composite pharmaceutical preparations. In aqueous-methanolic solution at pH 6.20–6.50 Al ions form stabile, orange chelates. Molar ratio L:Al. is 2:1 (TRIAP) or 3:1 (METRIAP) and stability constants, expressed by log K, are 12,604 (METRIAP) and 8,440 (TRIAP). Other components of these preparations, particularly Mg, do not disturb Al determination. The determination results were statistically calculated and compared with those obtained by the method of atomic absorption spectrophotometry (AAS). The advantage of the developed method is easy synthesis of reagents, simple analytical procedure, stability of formed complexes, good reproducibility and accuracy of results. Using TRIAP or METRIAP the elaborated spectrophotometric method is more accurate than AAS method, for defined purpose.