Abstract

The combination of normal phase and size exclusion separations with FT-IR detection has been successfully demonstrated and performed, with some restrictions. In these cases, the restrictions of IR transparency and volatility on the selection of mobile phases are a problem and do not permit a useful range of chromatographic selectivity. In particular, reversed-phase separation is more difficult. The recording of infrared spectra of components eluted from a high-performance liquid chromatograph (HPLC) requires the removal of these interferences from the mobile phase either by spectral subtraction or by evaporation of the solvent before the trace amount of solute analysis. Several works have attempted to develop techniques for automated on-line elimination of the mobile phase. The first micro-HPLC/FT-IR results were reported by Jinno and his co-workers as a buffer memory technique. More recently, a method has been developed in which the solvent from microbore HPLC is continuously sprayed onto and evaporated from a rotating reflective surface by a heated gas nebulizer. This method produced a spectrum of about 500 ng of 1,5-dihydroxynaphthalene. The solvent elimination technique for trace analysis has been a main concern in HPLC/FT-IR research; recently, microscope (micro)/FT-IR has become a major technique for trace or highly sensitive analysis. The greatest concern is the collection medium, as well as the question of how to make very small spots on the medium in solvent-elimination LC/FT-IR. The effects on the surfaces of materials were discussed by Griffiths and co-workers. We found that the spotted droplet on perfluorated polymer film reduces the diameter in accordance with solvent evaporation; in a few minutes at room temperature, the spot becomes sufficiently large to be measured by microscope/FT-IR. In this work, we are focusing on the microscale condensation technique in order to obtain picogram-level sample spectra by microscope/FT-IR. It is designated the "pin-point" condensation method.

Recent applications of FT-IR spectroscopy to polymer systems

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