High-Performance Thin Layer Chromatographic Method for the Simultaneous Quantitation of Melatonin and Zolpidem in Tablet formulation

A simple, accurate and precise densitometry method for the simultaneous estimation melatonin (MEL) and zolpidem (ZOL) in pharmaceutical dosage forms has been developed and validated. Separation of drugs was carried out using toluene: n-butanol:glacial acetic acid:water (1:4:2:2v/v/v/v) as mobile phase on precoated Silica Gel 60F₂₅₄ plates. The densitometry evaluation of spot was carried out at 254 nm. The R_f value for MEL and ZOL were found to be 0.87±0.01 and 0.59±0.01 respectively. The method was validated with respect to linearity, accuracy, precision and robustness as per the International Conference on Harmonization (ICH) guidelines. The drug response with respect to peak area was linear over the concentration range 150-900 ng/spot and 250-1500 ng/spot for MEL and ZOL respectively, limit of detection and limit of quantitation were found to be 14.96 ng/spot and 45.60 ng/spot for MEL and 19.53 ng/spot and 59.24 ng/spot for ZOL. The percentage recovery of MEL and ZOL were found be 99.04-99.35% and 98.11-98.77% respectively. The % RSD values for (intra-day RSD 0.26-0.56% and inter-day RSD 0.36-0.78 %for MEL and intraday RSD 0.18-0.31% and inter day 0.23-0.31% for ZOL). It was observed that the proposed HPTLC method could be used for efcient analysis and monitoring of the MEL and ZOL in combined tablet dosage forms.