Heteroatom Speciation in Coal Liquefaction Via FT-IR Coupled with Liquid Chromatography. Quarterly Progress Report, October 1-December 31, 1982

摘要

A liquid chromatographic, analytical-scale separation was optimized for neutral and slightly basic nitrogen compounds, phenols and alcohols. A Whatman PAC column was chosen because it was found that traditional strongly adsorbing molecules can be eluted from this column employing a reasonably IR transparent mobile phase with a small amount of polar modifier. When utilizing FTIR as a liquid chromatographic detector, it is important to consider both the chromatographic properties of the solvent used for the mobile phase and its infrared spectroscopic properties. If a solvent is not transparent over a relatively wide range of wavelengths or the solvent adsorbs in the region of several important functional groups, it will be a poor choice for the mobile phase. The mobile phase used here in conjunction with the PAC column was a binary phase of 98:2 CDCl sub 3 :CH sub 3 CN. The ir spectrum of this binary mobile phase is shown in Figure 2. It was found that phenols would not elute from the column with 100% chloroform with practical k' values unless a small amount of polar modifier was added. The use of deuterated chloroform shifted less absorbing ir bands to regions in which there was little interference with important functional groups. The amount of water present in the mobile phase and thus on the column was found to greatly affect the retention characteristics of the polar compounds. Therefore, eliminating water helped assure a constant level of column activation. The routine method of maintaining constant column activation in the normal phase mode by saturating the mobile phase with water could not be utilized here with ir detection due to the great absorptivity of water in the ir. Table I lists the polar models examined in this study and their retention volumes as obtained by single injection with CDCL sub 3 -CH sub 3 -CH sub 3 CN elution and uv (254 nm) detection. (ERA citation 08:011673)