HPLC Separation of Lysine and Arginine from Other Amino Acids using Zodiac HST C

Amino acids are polar ionic compounds that typically show poor retention on traditional reversed-phase columns without the use of ion-pairing reagents. In this application, lysine and arginine—which contain two amino groups—can be effectively separated from other amino acids using the Zodiac HST C mixed-mode column.

Amino acids with a pKa between 3 and 5 and containing one acidic and one basic functional group are highly polar and exhibit limited ion-exchange interaction with the Zodiac HST C stationary phase. In contrast, amino acids that possess two amino groups carry a net positive charge, enabling cation-exchange interaction with the column.

Mobile phase pH adjustment provides a powerful tool for fine-tuning selectivity, allowing effective separation of zwitterionic, basic, and acidic compounds. This method is particularly well-suited for distinguishing mono-charged species from those with additional charges.