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E-Journal of Chemistry
Volume 8, Issue 3, Pages 966-976

Combination of First Derivative Spectrophotometry and H-Point Standard Addition Method for Simultaneous Determination of Guaifenesin and Theophylline in Cough Syrup

R. Hajian, N. Shams, and Z. Davarpanah

Young Researchers Club, College of Science, Chemistry Department, Islamic Azad University Branch of Gachsaran, Gachsaran, 75818 63876, Iran

Received 20 February 2010; Accepted 15 April 2010

Copyright © 2011 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Combination of first derivative spectrophotometric and H-point standard addition method (HPSAM) has been applied for simultaneous determination of guaifenesin and theophylline. First derivative signals at the two pairs of wavelengths, 282.0-290.2 nm and 277.4-287.8 nm were monitored with the addition of standard solutions of both guaifenesin and theophylline in the ratio of 1:1. The method is able to accurately determine guaifenesin and theophylline (1:5 to 10:1) mole ratios. Accuracy and reproducibility of the determination method on the various amounts of guaifenesin and theophylline with known concentrations were evaluated in their binary mixtures. The recommended procedure was successfully applied to some cough syrups and synthetic mixtures with satisfactory results.