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Utilization of charge transfer complex formation for the spectrophotometric determination of piroxicam and tenoxicam

Fahad N.Assubaie

The molecular interaction between piroxicam and tenoxicam as electron donor and each of 7,7,8,8-tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as electron acceptor have been investigated spectrophotometrically. The coloured products are measured at 844, 393 and 459 nm for TCNQ; TCNE and DDQrespectively. Optimization of the different variables affecting the reaction is described. The TCNQ, TCNE and DDQ-based color systems were stable for 3 hrs in non-aqueous media and obeyed BeerÂ’s law over a wide range of concentration. The linear working ranges, apparent molar absorptivities, SandellÂ’s sensitivity indexes, detection and quantification limits were calculated for all systems. JobÂ’s plot of the absorbance versus the mole fraction of the drug indicated the formation of a 1:1 adducts. Application of the procedure to the analysis of various pharmaceutical samples gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique.