Transfer of Minilab TLC Screening Methods to Quantitative HPTLC-Densitometry for Pyrazinamide, Ethambutol, Isoniazid, and Rifampicin in a Combination Tablet

Individual HPTLC-densitometry methods for pyrazinamide, ethambutol, isoniazid, and rifampicin antituberculosis drugs in a combination tablet were developed by transfer of TLC screening methods contained in the Minilab manual from Global Pharma Health Fund E.V. for field use in identifying substandard and fake pharmaceutical products. Transfer was made using a model process published earlier. For ethambutol the transfer was essentially direct, but for the other three drugs lower sample and standard solution concentrations and a different mobile phase were needed. A CAMAG Linomat 4, Merck HPTLC premium purity silica gel 60 F254 glass plates, and a CAMAG Scanner 3 with winCATS software were used for assay of tablets for the four drugs and validation of the results of the new methods for linearity, accuracy, precision, peak identity, and peak purity.