Simultaneous Densitometric Determination of First Line Anti-TB Drugs in Binary, Ternary, and Quaternary Mixtures

Abstract

This article presents the development of a new densitometric method for the simultaneous separation and determination of isoniazid (INH), ethambutol (EMB), rifampicin (RIF), and pyrazinamide (PZA). INH, RIF, and PZA were determined by UV detection at 270 nm, and then EMB was derivatized and detected at 250 nm. The studied drugs were determined in their pure forms, available pharmaceutical preparations, binary, ternary, and quaternary synthetic mixtures. The study was performed on precoated silica gel TLC plates using acetonitrile:chloroform:2-propanol:4 N ammonia as a mobile phase (34:31:34:1 v/v/v/v). The studied drugs have been satisfactorily resolved with R_f values 0.31 ± 0.01, 0.48 ± 0.03, 0.73 ± 0.02, and 0.09 ± 0.01 for INH, RIF, PZA, and EMB, respectively. The developed method has been validated according to ICH guidelines providing good correlation coefficients (0.9991–0.9998) with a detection limit of 18.14 to 94.34 ng/band for all studied drugs. The proposed method has the potential to determine INH, RIF, and PZA simultaneously (before spraying) and EMB after spraying of the plate with cobalt sulfate without any interference. The method is new, rapid, and inexpensive compared to the official and reported methods for the assay of the quaternary mixture of the studied drugs.

Keywords:

• Cobalt sulfate
• densitometry
• ethambutol
• isoniaizd
• pyrazinamide
• rifampicin