PCM

Density functional theory (DFT) and Time dependent density functional theory (TDDFT) calculations have been carried out to study the electronic structure and the UV absorption spectra of Tolperisone. The UV spectra have been investigated with inclusion of solvent effect. The B3LYP functional with cc-pVDZ basis sets have been used for geometry optimization and also to compute absorption energies. The solvent effects have been included using the polarizable continuum model (PCM). The vertical absorption energies both in gas phase and in polar solvents such as water, methanol and ethanol were computed. The absorption maximum both in gas phase and in polar solvents is discussed in terms of electrostatic interaction energy, oscillator strength and dipole moment.

A simple, specific, selective and accurate stability-indicating reversed phase high performance liquid chromatographic method was developed for simultaneous determination of Diclofenac potassium (DIC), Paracetamol (PCM) and Methocarbamol (MET). An isocratic RP-HPLC was achieved on younglin HPLC system using Varian C18 (250 Χ 4.6 mm i.d, 5 μm particle size) column with the mobile phase containing mixture of Methanol:water (80:20,v/v). The flow rate was 0.8 ml/min and the eluent was monitored at 225nm. The retention times of DIC, PCM and MET were found to be 3.51, 6.42 and 9.90 min respectively. The linearity was established for DIC, PCM and MET in the range of 10-60 µg/ml, 65-390µg/ml, 100-600µg/ml respectively. The percentage recoveries of DIC, PCM and MET were found to be in the range of 99.73%±0.109, 99.59%±0.085 and 99.50%±0.16 respectively. The LOD for DIC, PCM and MET were found to be 0.15, 2.40 and 1.82μg/ml respectively, while LOQ were 0.48, 7.29 and 5.53μg/ml respectively. All three drugs were subjected to acid, alkali, oxidation, and dry heat degradation. The degradation studies indicated DIC, PCM and MET showed degradation in acid, alkaline, H2O2, and in dry heat condition. The degradation products of DIC, PCM and MET were resolved well from the pure drug with significant differences in their retention time values. This method was also successfully employed for simultaneous quantitative analysis of DIC, PCM and MET in bulk drugs and formulations. The developed method is stability indicating and separate degradants and can be used to determine the stability of samples.