First derivative spectrophotometric determination of weakly UV absorbing terfenadine and bencyclane

Rapid first derivative procedure is described for the determination of terfenadine and bencyclane in pure samples and in dosage forms. The method is based on the reaction of these drugs as n-electron donors with picric acid as ceta-acceptor, to form stable charge-transfer [CT] complexes. The coloured products are quantified by measuring the first derivative [D[1]] peak amplitude at 430 nm and at 425nm for terfenadine and bencyclane, respectively, or the peak-trough amplitude at 360-325 nm for terfenadine. Beer's law is obeyed over the concetration range 4-20 micro g ml[-1] of the investigated drugs. The proposed method is simple and sensitive. Reproducible, accurate and reliable results were obtained. The results were statistically compared with those of the standard methods. Terfenadine, alpha-[4-[1,1-dimethylethyl] phenyl]-4- [hydroxydiphenylmethyl] -1- piperidinebutanol, is a selective histamine H[1]-receptor antagonist used to relieve the symptoms of allergy. Bencyclane, N,N-dimethyl -3- [[1-[phenylmethyl]-cycloheptyl] oxy]-1-propanamine, is vasodilator which has been given in the treatment of peripheral and cerebral vascular disorders. Terfenadine and bencyclane are weakly UV absorbing compounds. Their [E 1%] ranged from 14.3-14.5 [1]. Therefore, the application of simple spectrophotometric methods is subjected to serious positive system error. To overcome this problem, many techniques have been reported [2-8]. Picric acid has been proved to be valuable reagent for the determination of some basic compounds [9,10]. Terfenadine and bencyclane have been also determined spectrophotometrically [11-15], coulometrically [16], GLC [17-20], HPLC [21,22] and radioimmunoassay [23.25]. This paper describes the application of the seta-acceptor picric acid [26] to the first derivative spectrophotometric determination of terfenadine and bencyclane as n-electron donors, in pure samples and in dosage forms

Doseamento espectrofotometrico do benciclan em medicamentos. / Spectrophotometric determination of bencyclane in dosage forms

Foram estudadas as condicoes experimentais para padronizacao de um metodo de doseamento de benciclan, baseado na precipitacao com reineckato de amonio, seguido de determinacao espectrofotometrica. O complexo vermelho formado apresenta picos de absorcao maxima em 400 e 520 nm. O metodo foi aplicado na analise de medicamentos e a precisao foi cerca de 2%