Study of Spectrophotometric Characteristics of the Charge Transfer Reaction of Aminomethylbenzoic Acid with 7,7,8,8-Tetracyanoquinodimethane

✍ Scribed by Shengyun Li; Xiuli Song; Yucui Hou; Wen Yuan

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 132 KB
• Volume: 29
• Category: Article
• ISSN: 0256-7660
• DOI: 10.1002/cjoc.201190161

✦ Synopsis

A new spectrophotometric method was developed for the determination of aminomethylbenzoic acid (PAMBA) using 7,7,8,8-tetracyanoquinodimethane (TCNQ). The method was based on the formation of charge transfer (CT) complex of this drug as n-electron donor with the π-acceptor TCNQ. TCNQ was found to react with PAMBA to produce a kind of yellow complex. The CT reaction proceeded quantitatively in pH 8.5 buffer solution. Different variables affecting the reaction were carefully studied and optimized. Under optimal reaction conditions, the stoichiometric ratio of the reaction, maximum absorption wavelength and the value of molar absorptivity were measured to be 1∶1, 425 nm, and 1.9×10 4 L•mol -1 •cm -1 , respectively. Beer's law was obeyed in the range of 1-9 µg•mL -1 of PAMBA. The data have been filled to a linear regression equation A＝-0.2612＋0.1123c (µg•mL -1 ), with a correlation coefficient of 0.9996. The detection limit was 0.4 µg•mL -1 , R.S.D. was less than 1.9%, and average recovery was over 97.6%. The formation of the CT complex was also confirmed by both infrared and 1 H NMR measurements. The thermodynamic property, kinetic property and reaction mechanism have also been discussed. The method developed was applied successfully to the determination of the subject drug in its pharmaceutical dosage forms with good precision and accuracy compared to official method revealed by t-and F-tests.