Determination of astemizole, terfenadine and flunarizine hydrochloride by ternary complex formation with eosin and lead(II)

A simple and sensitive spectrophotometric method has been established for t he determination of astemizole(I), terfenadine(II) and flunarizine hydrochl oride(III) based on ternary complex formation with eosin and lead(II). The method does not involve solvent extraction. The colour of the produced comp lex is measured at 547.5 nm for (I) and (III), while (II) is measured at 54 0.7 nm. Appropriate conditions were established for the colour reaction and for the eosin: Pb(II): drug ratio to obtain maximum sensitivity. Under the proposed conditions, the method is applicable over concentration range of 4.1-37.6, 11.8-47.2 and 2.4-19.1 mu g ml(-1) with mean percentage recovery of 99.20 +/- 0.63, 99.76 +/- 0.39 and 99.60 +/- 0.47% for (I), (II) and (II I), respectively. The suggested method was applied for determination of (I) , (II) and (III) in pharmaceutical preparations. Through the use of a non-i onic surfactant (methylcellulose), prior extraction of the drugs was unnece ssary. The results obtained demonstrated that the method is equally accurat e, precise and reproducible as the official or reported methods. For the pu rpose of enhancing the sensitivity, a fluorescence quenching method for det ermination of the studied drugs via ternary complex formation was also inve stigated. The detection limit for the studied drugs (I), (II) and (III) was 0.94-7.1 mu g ml(-1) with mean percentage recovery of 99.84 +/- 0.29, 99.2 4 +/- 0.36 and 99.34 +/- 0.26%, respectively. The results obtained by apply ing the proposed methods were statistically analyzed and compared with thos e obtained by official or reference methods. Unlike other reported ion-pair techniques, the suggested methods have the advantage of being applicable f or the determination of the three drugs in their pharmaceutical dosage form s without prior extraction. They are recommended for quality control and ro utine analysis where time, cost effectiveness and high specificity of analy tical techniques are of great importance. (C) 1999 Elsevier Science B.V. Al l rights reserved.