Direct Kinetic Stability-Indicating Densitometric Method for the determination of some Anti-Tuberculosis Drugs

: The current work describes the development and validation of a quantitative and a stability-indicating densitometric method for sensitive estimation of some anti-TB drugs, rifampicin (RIF), pyrazinamide (PZA) and isoniazid (INH). Precoated silica gel TLC aluminium plates were utilized as the stationary phase and the eluent comprised of two mobile phases were selected; chloroform-ethanol-isopropanol (4.5: 5.25: 5.25, v/v/v) and ethanol-chloroform- ammonia (33 %) (7: 7: 0.5 v/v/v). Densitometric analysis was achieved at λ max 270 nm for RIF, PZA and INH. Stress analysis was carried out under various reaction conditions including acid and base hydrolysis, oxidation, and photo-degradation. Compact spots of studied drugs were foundat R f values 0.35±0.01, 0.83±0.03 and 0.37±0.02 for INH, RIF and PZA respectively. The data of linear regression analysis indicated a good linear relationship over the range of 75-600, 150-900 and 75-600 ng/spot for INH, RIF and PZA respectively. The method was validated for robustness, precision and recovery. Limit of detection ranged from 4.84 to 32.2 ng/spot. Under various stressed conditions, RIF, PZA and INH showed degradation behavior. Peaks of a degraded products were well resolved with reasonably different R f values from the intact drugs. The degradation rate constants and half-lives have been determined for each reaction.