Petrus Hemström

Alternative organic solvents for HILIC separation of cisplatin species with on-line ICP-MS detection

Several low volatile organic solvents were evaluated as organic modifiers in eluents for HILIC separations of cisplatin species to optimize the on-line coupling of HILIC to inductively coupled plasma MS (ICP-MS). The aim was to identify a solvent giving low solvent vapor loading of the ICP, to maximize analyte sensitivity and minimize carbon depositions on instrumental parts, while retaining chromatographic performance. The best overall performance of the HILIC-ICP-MS system for the analysis of cisplatin was achieved using 1,4-dioxane as eluent, yielding high retention and an HILIC type retention mechanism, at the expense of a 50% drop in column efficiency due to the higher viscosity of 1,4-dioxane compared to the more commonly used HILIC solvent ACN. Using 1,4-dioxane as solvent in HILIC provides the best compromise between carbon deposition and separation efficiency among a series of high-boiling water-miscible solvents tested.

Preparation of a sorbitol methacrylate grafted silica as stationary phase for hydrophilic interaction chromatography

A new highly hydrophilic stationary phase based on graft polymerization of sorbitol methacrylate from the surface of Kromasil silica particles is described. Polymerization was initiated by thermal cleavage of tert-butyl hydroperoxide covalently attached to the silica particle surface. Due to the highly amphiphilic properties of the monomer, an extensive search was needed to find solvent conditions that enabled surface-initiated polymerization. This was finally solved by using a mixture of solvents that only partially dissolved the monomer. The graft polymerization was confirmed by Fourier transform infrared spectroscopy and elemental analysis. The resulting stationary phase was evaluated by HPLC and exhibited a selectivity markedly different from that of commercially available columns and of neat silica.