A stock standard solution of DZL was prepared by dissolving 100 mg of pure DZL in a 100 mL volumetric flask using HPLC grade water.
From a DZL ophthalmic solution, 1 mL of the test sample was transferred into a 100 mL volumetric flask, sonicated with mobile phase for 10 minutes, and made up to the volume with the same solvent mixture.
In liquid chromatographic method development for the determination of DZL, various parameters such as detection wavelength, effect of composition of mobile phase, pH of mobile phase, flow rate, concentration of buffer solution, column temperature, and injection volume were studied and optimized.
System suitability studies were conducted by injecting DZL standard solutions in six replicates and system suitability parameters such as USP plate number, 2910; tailing factor, 1.08; and retention time, 2.653 [+ or -] 0.0461 minutes (SD) were determined, which indicated satisfactory results.
The absence of interfering peaks of additives in a pharmaceutical formulation at the retention time of DZL proved the specificity of the method.
Linearity was evaluated by analyzing a series of various concentrations of DZL. Six concentrations (10,25,50, 100, 125, and 150 [micro]g/mL) of DZL were injected in triplicate.
Percent recoveries ranged from 99.53% to 100.32%, which indicate the excipients in ophthalmic preparations do not interfere with DZL assay (Table 1).