Simultaneous Determination of Guanidine and Sodium Ion Using Mixed-Mode HPLC

This method demonstrates the analysis of guanidine and sodium ion (Na⁺) using the Zodiac HST OG column, which offers mixed-mode retention combining reversed-phase and ion-exchange interactions. The optimized separation was achieved on a 50 × 4.6 mm, 5 µm Zodiac HST OG column using a mobile phase of MeCN/H₂O/TFA – 25/75/0.05, at a flow rate of 1.0 mL/min.

Detection was performed using Evaporative Light Scattering Detection (ELSD) for non-chromophoric ions and UV at 200 nm for guanidine. The method allows for fast and effective separation of small polar analytes and inorganic cations within a short runtime, making it ideal for quality control and reaction monitoring involving guanidine salts or buffers.