Surface‐Grafted Polyamide Stationary Phase on poly(styrene‐divinylbenzene) Microspheres for Hydrophilic Interaction Chromatography

An amide-functionalized stationary phase for hydrophilic interaction chromatography was developed by surface-confined grafting of N-vinylformamide onto poly(styrene-divinylbenzene) microspheres. The grafting reaction was restricted to the microparticle surface by selecting a polar monomer (N-vinylformamide) and a non‑swelling reaction solvent (ethanol), preventing monomer penetration into the polymer matrix. The resulting stationary phase exhibited typical HILIC retention behavior and provided effective separation of polar model analytes, including nucleosides, amino acids, and vitamins, with a plate count of up to 41 980 plates per meter for cytosine. The phase demonstrated excellent hydrolytic stability across a wide pH range (2-10) and extremely low column bleed. Under gradient elution with up to 50% aqueous content, baseline drift was negligible-comparable to that of a blank, and significantly lower than that of commercial silica‑based amide columns.