Coupling of Reversed-Phase Liquid Column Chromatography and Fourier Transform Infrared Spectrometry Using Postcolumn On-Line Extraction and Solvent Elimination

Abstract

An on-line postcolumn extraction module was used in conjunction with a solvent elimination interface for the semi-on-line coupling of reversed-phase liquid chromatography (RP-LC) and Fourier transform infrared spectrometry (FT-IR). The extraction module consisted of a phase segmentor, an extraction coil, and a phase separator. Dichloromethane was used as extraction solvent. The organic phase delivered by the separator was evaporated by a spray-jet assembly that simultaneously deposited the extracted analytes onto a zinc selenide window, which was subsequently analyzed by FT-IR microscopy. The method is evaluated by studying parameters such as postcolumn band broadening, phase separation efficiency, evaporation efficiency, extraction yield, eluent composition, and use of nonvolatile buffer salts. Good-quality spectra were obtained for test compounds (phenylureas and quinones), which were separated by RP-LC using a buffered eluent with high water content. Large-volume injections allowed FT-IR detection at the submicrogram per milliliter level.