Spectrophotometric Determination of Some Phenolic Compounds by Formation of Copper(II) Complexes

摘要

Simple and sensitive specfrophotometric method is described for the determination of phenolic compounds in both in pure form and in pharmaceutical preparations. The method is based on the formation of a new ligand from the reaction between 4-aminoantipyrine with phenolic compounds and then reacts with copper (II) to give a colored complex at room temperature. The maximum absorbance of the prepared complexes were measured at 450,500 and 480 nm for pyridoxine, resorcinol and phloroglucinol complexes respectively. Beer's law was obeyed in the concentration range of 1.5-20, 2.5-30 and 2.0-25 pg/ml~(-1), the molar absorptivity values are 2.4778 x 104,1.6740x104 and 1.7001 x 104 L mol~(-1) cm~(-1) , the Sandal sensitivity values are 0.0501xl0"3,0.1740x10~(-3)and 0.1228x1010~(-3)ug cm~(-2) for Pyridoxine, resorcinol and phloroglucinol complexes respectively. The correlation coefficients were 0.9999, 0.9998 and 0.9999, the limits of detection(LOD) were 0.47793, 0.15125 and 0.01434ug ml~(-1) , the limits of quantification were (LOQ) 1.4482, 0.45833 and 0.04347 for pyridoxine, resorcinol and phloroglucinol complexes respectively. The stoichiometry of the complexes formed (1:2) was determined by Job's continuous variations method and molar ratio method. Furthermore the stability constant (K) and Gibbs free energy (AG) for the complexes were also calculated. The proposed methods were applied successfully for the determination of phenolic compounds in commercial tablets.