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A stability‐indicating reversed‐phase high‐performance liquid chromatography method for simultaneous estimation of dolutegravir sodium and lamivudine encapsulated in the nanoliposomal formulation was developed. The chromatographic parameters namely, organic phase ratio, flow rate, and sample injection volume were selected as independent factors and were optimized by multivariate Box–Behnken design. Responses analyzed were retention time, peak area, and resolution. The optimized chromatographic method with Hypersil BDS C8 CN column as stationary phase and methanol and acetonitrile mixture and acidified Milli‐Q water (pH 2.8, adjusted with 0.02% v/v orthophosphoric acid) as the mobile phase in an isocratic elution mode was validated according to parameters of International Conference on Harmonization Q1(R2) guidelines. The validated reversed‐phase high‐performance liquid chromatography method exhibited specificity for both dolutegravir sodium and lamivudine in the presence of degradation products as well as the liposomal matrix. This method was effectively utilized to determine the amount of drug entrapped and drug loading efficiency of dolutegravir sodium and lamivudine in a nano‐liposomal formulation.

Stability-indicating reverse-phase HPLC analytical method for the quantification of Paclitaxel (PTX) in the bulk and cationic liposomes was developed. The optimized method was validated according to the ICH Q2 (R1) guidelines by following a 2-level–4-factor interaction Box–Behnken design using Design-Expert® software. The responses measured at 228 nm were retention time (Rt), peak area, tailing factor (Tf10%), and the number of theoretical plates (NTP). PTX was eluted best using the Luna® C18 LC Column along with a mobile phase of methanol and 25 mM ammonium acetate buffer (pH 6) 75:25 v/v mixture at 25 ± 2 °C temperature. The currently developed method was linear in the 2.5–100 µg/mL range with a detection limit of 0.062 µg/mL and a quantification limit of 0.188 µg/mL. The optimized method was utilized to evaluate the stability of PTX in different stress conditions by performing forced degradation studies. The results from the degradation study stipulated that on exposure to various stressors, namely acid, alkali, oxidative, thermal, and UV light, the PTX did not show considerable degradation except alkali exposure. Further, the method was successfully used for the quantification of PTX in cationic liposomes. The particle size, zeta potential, and polydispersity index of the PTX-loaded liposomes were 219.25 ± 7.566 nm, 57.15 ± 12.374 mV, and 0.807 ± 0.1958 respectively. The percent of drug entrapped was quantified and was found to be 59 ± 1.414%.

A novel isocratic stability-indicating chromatographic method was developed, optimized and validated using Design-Expert® following ICH guidelines for the quantification of Timolol maleate (TM). The intrinsic stability of TM was assessed by force degradation studies, which concluded no extensive degradation except under alkaline and oxidative conditions. TM was quantified accurately in the surfactant-based elastic vesicular system by separating it on Hypersil BDS C8 column using triethylamine in H2O (0.15%v/v; pH 3.0) and acetonitrile (ACN; 65:35%v/v). The influence of variable factors like mobile phase pH, injection volume (μL), flow rate (mL/min) and ACN content (%) on method responses were assessed using a full factorial design. The method was linear between 0.05 and 10 μg/mL with an R2 value of 0.9993. Limit of detection and limit of quantification were found to be 0.90 and 27.2 ng/mL. The method was specific, with recovery in plain drug solution of 89–92% and elastic nanovesicles of 90–93%. The experimental model was significant (P < 0.0001) as indicated by deliberate changes in the method analyzed through analysis of variance. The total drug content in elastic nanovesicles was estimated to be 9.53 ± 0.01 mg/20-mL dispersion and entrapment efficiency was 44.52 ± 0.73%. The developed method was rapid, economic and precise for the quantification of TM in bulk and vesicular system.

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