Repeatability studies were performed by analyses of three different concentrations of the drug in hexaplicate on the same day. Intermediate precision of the method was checked by repeating the studies on three different days. The results of repeatability and intermediate precision experiments are shown in Table 1. The developed method was found to be precise as the RSD values for repeatability and intermediate precision check details studies were less than 0.51% and 0.50%, respectively. Accuracy of the method was evaluated by fortifying a mixture of decomposed reaction solutions with three different concentrations of the drug.
The mixtures were analyzed in triplicate and the percentage of added drug obtained from difference between peak areas of fortified and unfortified degraded samples of drug was found to be 99.86–100.35% [Table
2]. To determine the robustness of the method, experimental conditions were purposely altered. Three parameters selected were flow rate, detection wavelength and solvent from different lots. The mobile phase flow rate was 1 ml/min. This was changed to 1.1 and 0.9 ml/min and the effect was studied. pH of mobile phase was varied within +, −0.2 unit of optimized pH. Also methanol of different lots from same manufacturer was used. When the effect of altering one set of conditions was tested, the other conditions were held constant at the optimum values. In all the deliberate varied chromatographic conditions, no significant change in retention time and tailing factor of paliperidone was Luminespib datasheet Dipeptidyl peptidase observed. The summary of results is shown in Table 3. The system suitability parameters with respect to theoretical plates, capacity factor, resolution factor, asymmetry factor were calculated and are given in Table 4. It could be seen from Table 4 that all the peaks were well resolved. The drug was degraded in acidic hydrolytic condition to 20% to form product II. Also in
alkali stress, the drug degraded to 26% to form product III. The degradation products formed under photoacidic and photoneutral conditions were overlapped in the chromatogram to show only one peak of product I. However, rate of degradation was 24% under photoacidic and 16% under photoneutral. The chromatogram of the mixture of degraded samples is shown in [Fig. 2A]. The drug was stable under all other stress conditions, including heating in water, oxidation, exposure of alkali solutions and solid drug to light, and dry heating at 50 °C. The assay content of paliperidone, commercially available marketed formulation was analyzed by the proposed method after exposure to accelerated storage condition (i.e. 40 °C/75% RH). The peak at retention time 8.4 min for the drug was observed in the chromatogram of the drug samples extracted from tablets and no additional peak was found [Fig. 3].