Capillary electrophoresis–contactless conductivity detection for routine screening of PDE-5 inhibitor adulterants in sexual-enhancement supplements

Abstract

Undeclared phosphodiesterase type 5 (PDE-5) inhibitors in sexual-enhancement supplements remain a public health and regulatory concern, creating demand for rapid and affordable screening methods suitable for routine control. A capillary electrophoresis method with capacitively coupled contactless conductivity detection (CE-C4D) was developed for simultaneous determination of sildenafil, homosildenafil, hydroxyhomosildenafil, and avanafil. Separation was performed in a 60 cm × 50 µm i.d. fused-silica capillary (35 cm effective length) using 20 mM Arg/MES containing 30% (v/v) acetonitrile at pH 6.00, a voltage of 18 kV, and hydrodynamic injection by siphoning at 20 cm for 90 s. Matrix-matched calibration showed excellent linearity up to 60 ppm for all analytes (R² > 0.99). In a surrogate supplement matrix, limits of detection and quantification were 0.59–0.86 ppm and 1.96–2.87 ppm, respectively. Precision and accuracy were suitable for screening, with repeatability and reproducibility below 10% RSD and recoveries of 102–106%. Eight commercial products were analyzed; four samples contained sildenafil, and one also contained homosildenafil, despite the absence of label declaration. Results agreed with the reference LC-MS/MS method, with deviations below 10%. These findings support CE-C4D as a practical first-tier tool for regulatory screening of PDE-5 inhibitor adulteration in health supplements.