Hydrophilic interaction liquid chromatography (HILIC) coupled to inductively coupled plasma mass spectrometry (ICPMS) utilizing a mobile phase with a low-volatile organic modifier for the determination of cisplatin, and its monohydrolyzed metabolite

Abstract

This study demonstrates the on-line coupling of hydrophilic interaction liquid chromatography (HILIC) to inductively coupled plasma mass spectrometry (ICPMS). A low volatile organic solvent, dimethylformamide (DMF), was used as organic modifier of the mobile phase to minimize the solvent loading of the ICP and thereby improve analyte sensitivity and method robustness. The concept was illustrated by the selective determination of cisplatin (cis-DDP), and its mono-hydrolyzed metabolite (MH-DDP). Species were separated on a 2.1 × 150 mm ZIC-HILIC column and detected on-line by selective platinum (m/z 194 and 195) monitoring, giving a detection limit of 2 pg Pt (0.2 ng ml⁻¹). Compared to the use of the conventional solvent acetonitrile (AcN), with DMF, cis-DDP sensitivity was enhanced as much as 36 times and no addition of oxygen to the plasma was needed to avoid carbon depositions on instrumental parts. Furthermore, several non-identified platinum containing compounds were observed when using AcN as a result of unwanted reactions between this solvent and the analytes. No such species were observed when DMF was used. The molecular structures of eluting compounds were verified by electrospray ionization mass spectrometry. Combined with a simple sample treatment protocol, the HILIC-ICPMS system allowed determination of free intracellular cis-DDP in in-vitro grown T289 human malignant melanoma cells up to 60 min after exposure to 50 μg ml⁻¹ cis-DDP for 1 h. This work shows that HILIC-ICPMS is a potent hyphenated technique for the analysis of hydrophilic metal compounds and that the use of chromatographic mobile phases with low-volatile organic solvents may be a generic approach to improve analyte sensitivity and system robustness of HPLC-ICPMS when mobile phases with high amount of organic solvent are used.