Impact of filter selection on UPLC quantification of terbinafine hydrochloride: Optimization of sample preparation...

This study aimed to validate an ultra-performance liquid chromatography method for the identification and quantification of terbinafine hydrochloride, an antifungal agent widely used in the treatment of dermatophyte infections. Accurate quantification of terbinafine hydrochloride in pharmaceutical samples is essential for quality control and regulatory compliance. In addition to method validation, the influence of syringe filter selection during sample preparation on analytical accuracy was systematically evaluated. Hydrophilic polytetrafluoroethylene membranes (0.22 μm) demonstrated superior performance, yielding higher and more consistent analyte concentrations compared to hydrophobic filters. This behavior may be explained by reduced non-specific adsorption of protonated terbinafine during filtration. In aqueous media, the analyte is predominantly present in its protonated form, which can increase its interaction with polar surfaces. In contrast, the surface-modified hydrophilic membrane likely minimizes these interactions, reducing analyte loss and improving recovery. The validated method showed consistent analytical performance, with linearity over the tested range (r² = 0.9981), low limits of detection (0.08 mg·mL^-1) and quantification (0.25 mg·mL^-1), high precision (relative standard deviation <2%), and recovery values between 98.0% and 102.0%. Robustness testing confirmed that small variations in flow rate, column temperature, and mobile phase composition did not significantly affect quantification. These results demonstrate that syringe filter selection is a critical parameter in terbinafine hydrochloride analysis and highlight the importance of optimized sample preparation in pharmaceutical quality control.