Stress degradation studies and development of validated stability indicating densitometric method for estimation of alpha lipoic acid in bulk and capsule dosage form

A precise, sensitive, specific and accurate stability indicating densitometric method was developed and validated for alpha-lipoic acid (ALA) in bulk and capsule dosage form. The study employed pre-coated silica gel 60F254 TLC plates as stationary phase and toluene: chloroform: methanol: formic acid (5:3:1:0.05; v/v/v/v) as mobile phase. The developed method furnished compact spots of alpha-lipoic acid (Rf 0.28 ± 0.05) after derivatization, offered good linearity in range 80–400 ng/spot with correlation coefficient of 0.998. The values for detection and quantitation were found 18.022 and 54.612 ng/spot respectively. ALA was subjected to stress degradation studies and total 13 degradation products were resolved. Thus, the proposed method offered good results according to ICH guidelines, and can be used for identification, routine quantitative determination as well as for monitoring the stability of ALA in bulk and in capsules.