eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-04-29 5 2 871 873 8690 article C. Bala Sekaran 1 A. Prameela Rani2 2 P.V.S. Mahesh 1 D. Kiran Kumar 1 Y. Sai Kiran 1 Department of Biotechnology, P. B. Siddhartha College of Arts & Science, Vijayawada - 520 010 (India). Department of Pharmaceutics, K.V.S.R. Siddhartha College of Pharmaceutical Sciences, Vijayawada - 520 010 (India). A simple, sensitive and reproducible spectrophotometric method was developed for the determination of thyroxine sodium in bulk and in pharmaceutical formulations. This method is based on the measurement of blue coloured species formed when phosphomolybdic acid present in Folin Ciocalteau reagent is reduced by the thyroxine sodium in the presence of sodium carbonate, having maximum absorption at 730nm. Beer’s law is obeyed in the range of 5-25 μg/mL. Results of analysis were validated statistically and by recovery studies. This method was successfully employed for the determination of thyroxine sodium in various pharmaceutical preparations and biological samples. https://www.biotech-asia.org/vol5no2/spectrophotometric-determination-of-thyroxine-sodium-with-folin-ciocalteu-reagent-in-bulk-and-pharmaceutical-formulations/ Thyroxine sodium; Visible Spectrophotometric determination; Beer’s Law; Sandell’s sensitivity