Development and validation of a stability-indicating HPLC method for simultaneous determination of salicylic acid, betamethasone dipropionate and their related compounds in Diprosalic Lotion.

Diprosalic Lotion is an anti-inflammatory drug product that contains salicylic acid and betamethasone dipropionate as active pharmaceutical ingredients (APIs). A reversed-phase high performance liquid chromatography (RP-HPLC) method was developed for simultaneous determination of salicylic acid, betamethasone dipropionate, and their related compounds in Diprosalic Lotion. A 150 mm x 4.6 mm I.D. YMC J'sphere ODS-H80 column at 35 degrees C and UV detection at 240 nm was used. A gradient elution was employed using 0.05% (v/v) methanesulfonic acid solution and acetonitrile as mobile phases. A total of thirty three compounds from Diprosalic Lotion samples were separated in 38 min. The stability-indicating capability of this method has been demonstrated by the adequate separation of all the impurities and degradation products in expired stability samples of Diprosalic Lotion. The method was validated as per the current ICH guidelines.

Influence of microwave irradiation on the intraparticle diffusion of an insulin variant in reversed-phase liquid chromatography under linear conditions.

The influence of microwave irradiation on the mass transfer kinetics of an insulin variant in reversed-phase liquid chromatography (RPLC) was investigated. The elution band profiles of insulin were obtained by the pulse-response method, under linear conditions. The RPLC column was placed in a microwave oven and the incremental change in the temperature of the column effluent stream at various microwave energies and mobile phase flow rates were measured. The microwave energy dissipated in the column was set at 15 and 30 W and the mobile phase flow rate was varied from 1.0 to 2.5 mL/min at a mobile phase composition of acetonitrile, water, and trifloroacetic acid (31:69:0.1, v/v/v). The experimental data were analyzed using the conventional method of moment analysis and the lumped pore diffusion model. Regardless of mobile flow rates, the effluent temperatures measured at 15 and 30 W microwave power input were 25+/-1 and 30+/-1 degrees C, respectively. The effect of microwave irradiation on the mass transfer of the variant insulin was determined by comparing the band profiles obtained under the same experimental conditions, at the same column temperature, with and without irradiation. The calculated intraparticle diffusion coefficient, D(e), at 30 W (30+/-1 degrees C) microwave irradiation was ca. 20% higher than without irradiation at 30+/-1 degrees C. These preliminary results suggest that microwave irradiation may have a significant influence on the intraparticle diffusion of insulin in RPLC.

Comparison of chromatographic band profiles obtained under microwave irradiated and non-irradiated reversed-phase liquid chromatography column.

The possible influence of the application of microwave energy to a reversed-phase liquid chromatography column on the mass transfer kinetics and the thermodynamics of equilibrium between mobile and stationary phases was examined. Chromatograms of propylbenzene and phenol were recorded under the same experimental conditions, on the same column, successively irradiated and not. The effect of microwave irradiation on the mass transfer kinetics was determined by measuring the second moment of small pulses of propylbenzene in a 70:30 (v/v) solution of methanol in water and microwave outputs of 15 and 30 W. The effect of microwave irradiation on the equilibrium thermodynamics was determined by measuring the elution time of breakthrough curves of phenol at high concentrations in a 20:80 (v/v) solution of methanol and water and microwave outputs of 15, 50, and 150 W. A qualitative comparison of the profiles of the propylbenzene peaks obtained with and without irradiation suggests that this irradiation affects significantly the peak shapes. However, a qualitative comparison of the profiles of the breakthrough curves of phenol obtained with and without irradiation suggests that this irradiation has no significant effect on their shapes. The peak sharpening observed may be due to an increase in the diffusivity, resulting from the dielectric polarization under microwave irradiation. This effect is directly related to an increase of the rate of mass transfers in the column. In contrast, the similarity of the overloaded band profiles at high concentrations suggests that the equilibrium thermodynamics is unaffected by microwave irradiation. This may be explained by the transparence of the stationary phase to microwaves at 2.45 GHz. The column temperature was measured at the column outlet under irradiation powers of 15, 30, 50, and 150 W. It increases with increasing power, the corresponding effluent temperatures being 25+/-1, 30+/-1, 35+/-1, and 45+/-1 degrees C, respectively.

Effect of microwave dielectric heating on intraparticle diffusion in reversed-phase liquid chromatography.

The influence of microwave (MW) irradiation on the mass transfer kinetics in reversed-phase liquid chromatography (RPLC) was studied by placing a column in a microwave oven and measuring the incremental change in the temperature of the column effluent stream at various microwave energies and mobile phase compositions. The microwave energy dissipated in the column was set between 15 and 200 W and the mobile phase composition used varied from 100 to 70, 50, and 10% methanol in water at 1.2 mL/min. At all the mobile phase compositions considered, the effluent temperature increased with increasing microwave energy. At 70% methanol, the mobile phase flow rate was set at 1.2, 2.0, and 2.8 mL/min. At 1.2 mL/min, the effluent temperatures at the lowest (15 W) and highest (200 W) microwave energy inputs were 25 +/- 1 degrees C and 41 +/- 1 degrees C for pure methanol, 25 +/- 1 degrees C and 48 +/- 1 degrees C for 70% methanol, 25 +/- 1 degrees C and 50 +/- 1 degrees C for 50% methanol, and, 25 +/- 1 degrees C and 52 +/- 1 degrees C for 10% methanol, respectively. With 70% methanol and microwave energy inputs of 15, 30, and 50 W, the effluent temperature did not change with increasing flow rate; a considerable change was observed at 100, 150, and 200 W between 1.2 and 2.0 mL/min and none between 2.0 and 2.8 mL/min. Chromatographic elution band profiles of propylbenzene were recorded under linear conditions, in 70% methanol solutions, for microwave energy inputs of 0, 15 and 30 W, at constant temperature. The intraparticle diffusion coefficient, De, under microwave irradiation was ca. 20% higher than without irradiation. These preliminary results suggest that microwave irradiation may have a considerable influence on intraparticle diffusion in RPLC.