0; 0.01 M) (B) in a gradient mode. The solvent program was set as follows: (Tmin/A:B; T0/60:40; T8.0/60:40; T10/50:50; T13/60:40; T16/60:40). The flow rate of 1.0 ml/min, column temperature

at 25 °C, injection volume of 20 μl and wavelength of 280 nm were found to be suitable to achieve the separation of paliperidone and its degradation products. Validation of the optimized LC method was done with respect to various parameters outlined in ICH guideline selective HDAC inhibitors 13 and was extended to LC–MS2 studies. The chromatographic conditions used for LC–MS analyses were the same as that for LC–PDA analyses, except that injection volume was 10 μl. LC–MS studies were carried out using positive as well as negative atmospheric pressure chemical ionization (+APCI and −APCI) modes in the mass range of 50–2000 m/z. High purity helium was used as carrier gas and nitrogen was used SP600125 datasheet as nebulizer. The operating conditions for LC–MS scans of drug and degradation products in both the ionization modes were optimized as follows: Rf loading: 80%; capillary voltage, 80 V; syringe volume, 250 μL; spray chamber temperature, 50 °C; nebulizer pressure, 35 psi; drying gas temperature, 300 °C; drying gas pressure, 10 psi; vaporizer gas temperature, 350 °C; vaporizer gas pressure, 20 psi; spray shield voltage (±), ±600.0 V. Specificity is the ability of the analytical method to measure the analyte concentration accurately

in presence of all potential degradation products. Specificity of the method towards the drug was studied by determination of purity for drug peak in stressed sample using a PDA detector. The study of resolution factor of the drug peak from the nearest resolving degradation product was also done. Drug as well as degradation product

peaks were found to be pure from peak purity data. Also, the resolution factor for the drug from degradation peak was greater than 3. Peak purity and resolution factor data is given in Table 4. Linearity test solutions were prepared from stock solution at seven concentration levels of analyte (5, 50, 100, 200, 400, 600, 800 μg/ml). The peak area versus concentration data was performed by least squares linear regression analysis. The calibration curve was drawn by plotting paliperidone out average area for triplicate injections and the concentration expressed as a percentage. Linearity was checked over the same concentration range for three consecutive days. Good linearity was observed in the concentration range from 5 to 800 μg/ml of paliperidone. The data was subjected to statistical analysis using a linear regression model; the linear regression equation and correlation coefficient (r2) were y = 1.0617x + 2.6806 and 0.9995, respectively. These results indicate good linearity. The LOD and LOQ for PPD were estimated at a signal-to-noise ratio of 3:1 and 10:1, respectively. The LOD and LOQ were 0.32 μg/ml, 0.99 μg/ml, respectively.