eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-04-21 6 1 397 399 8462 article G. Vijaya Raja 1 S. Lalitha Devi 2 K. R. S. Sambasivarao 3 Centre for Biotechnology, Acharya Nagarjuna University, Nagarjunanagar - 522 510 (India). Department of Biochemistry, Sri Venkateswara Institute of Medical Sciences, Tirupati - 517 507 (India) Centre for Biotechnology, Acharya Nagarjuna University, Nagarjunanagar - 522 510 (India). In the present study the authors were developed three simple, economic and sensitive spectrophotometric methods for the assay of phenazopyridine hydrochloride either in pure form or pharmaceutical formulations .The described methods are based on the formation of colored chloroform extractable ion-pair complex of the drug with bromophenol blue (Method A), Amidoblack (Method B) and Bromothymol blue (Method C) in acidic medium. The extracted chromagen complexes showed absorbance maxima at 370nm, 620nm and 400nm respectively. These methods permitted determination of the studied drug over a concentration range 1-5 μgml with molar absorptivity of 3.73 X 104, 3.241 X 104 and 5.437 X 10 4 Lmole-1cm-1 respectively. These methods have been successfully applied for the assay of the drug in pharmaceutical formulations. No interference was observed from common pharmaceutical adjuvents. Results of analysis were validated statistically and through recovery studies and were in good agreement with those obtained by the official and reference methods. https://www.biotech-asia.org/vol6no1/aplication-of-some-anionic-dyes-for-the-spectrophotometric-determination-of-phenazopyridine-hydrochloride/ Phenazopyridine; absorbance maxima; ion-pair complex