2-Chloro-1-methylquinolinium tetrafluoroborate as an effective and thiol specific UV-tagging reagent for liquid chromatography

Abstract

A new, highly reactive, and thiol specific derivatization reagent for liquid chromatographic analysis has been developed. The reagent, 2-chloro-1-methylquinolinium tetrafluoroborate, reacts instantaneously with hydrophilic thiols in water under mild conditions. The 2-S-quinolinium derivatives, resulting from this reaction, are stable thioethers exhibiting well defined absorption maximum at 348 nm and molar absorptivity coefficient about 2 × 104 L mol -1 cm-1. It is shown that under reversed-phase high performance liquid chromatography conditions with gradient elution, six thiols possessing different functional groups, can be baseline separated and quantified within 4 rain in one analytical run. The lower limits of detection and quantitation of the analytes (20 μL injection volume) are within 0.3-1.5 pmol and 0.5-4.0 pmol, respectively. The assays are linear in the range of 0.025-8 nmol/mL with correlation coefficients values close to 0.9999. Synthesis of 2-chloro-1-methylquinolinium tetrafluoroborate, as well as isolation of the 2-S-quinolinium derivative of one model thiol, are described.