Normal-phase liquid chromatography/Fourier transform infrared spectrometry for analysis of nonpolar material with semipreparative, analytical, and microbore columns

Abstract

Results which have evolved from an evaluation of HPLC/FTIR employing semipreparative, analytical, and microbore scale separations are presented. Normal-phase chromatography on silica gel has been carried out with Freon-113 elution. Model mixtures of aliphatic and aromatic hydrocarbons and nonpolar constituents In coal liquefaction process solvents have been separated. Best results have been obtained with the semipreparative and microbore modes because of the higher sample concentration developed at the detector. This study has shown the feasibility of microbore HPLC/FTIR which will enable chromatographers to economically use exotic solvents with large infrared windows.Identification of nonvolatile components in a thorough complex mixture analysis has always been one of the most demanding tasks for the analytical chemist to perform. Approaches to these analyses have been facilitated by the increasing technological level of chromatography. High-performance liquid chromatography (HPLC) has been particularly enhanced by the development of more efficient columns and by the employment of a variety of highly specific detectors. Continuing sophistication in small-bore column technology may lend itself nicely to those complex separation problems that require very high column efficiency in order to achieve the necessary high resolution (1). Multiple, simultaneous, selective detection allows detailed information to be obtained for chromatographically unresolved components (2). Unconventional information-rich spectroscopic detectors can potentially provide highly specific data for less than adequate complex mixture separations (3). The application of infrared (4), nuclear magnetic resonance (5), inductively coupled plasma atomic emission (6), and mass spectrometry (7) to chromatography, however, is not without experimental problems. Compatible spectroscopic-chromatographic solvents, minimal dead volume between column and detector, and reasonable detection limits are but a few of these prob-

Size-exclusion chromatography and size-exclusion chromatography/Fourier transform infrared spectrometry of reacting organofunctional trialkoxysilanes

“…The combination of liquid chromatography and FT-IR was introduced by Griffiths et al (28) and is beginning to see widespread application (29)(30)(31)(32). There are two general approaches to the LC/FT-IR interface which include solvent elimination (28, 33-37) and flow-cell (38,39) techniques.…”

Combinatorial Chemistry Libraries, Analysis of

“…The use of microbore columns can help overcome the sensitivity limitations associated with the use of short pathlength flow cells in HPLC/FTIR. 54 A schematic diagram of a zero dead volume flow cell designed for microbore HPLC/FTIR is shown in Figure 9. 55 This flow cell has a pathlength of 0.45 mm, an internal volume of 0.33 µL, and can detect less than 50 ng of 2,6-di-tert-butylphenol at 3641 cm 1 .…”

Other Modes of Detection

“…Deuterated solvents, although expensive, are some times used, particularly in micro-HPLC, because they give larger solvent win dows and may give better separations. Freon 113 (l,l,2-trichloro-l,2,2-trifluoroethane) has also been used because of its IR spectral windows [91]. Deuterated solvents studied include heavy water [86][87][88][89], deuteriobenzene [87], deutero- methanol [86,89], 90% deuteroacetonitrile with 10% heavy water [88], and deuterochloroform with a deuteromethanol modifier [90].…”