Liquid chromatography and FTIR spectrometry separately and in combination are well known analytical techniques. In liquid chromatography, a sample and a solvent are pumped through an LC column which separates the sample into its constituents or components causing them to flow out of or efflux from the LC at different times. The effluent passes through a detector which produces a signal that can be recorded as a chromatogram. The signal associated with the components produce peaks and the components from the LC are sometimes called "eluting peaks". While a chromatogram provides information useful for analyzing the sample components, it is sometimes desirable to further analyze eluting peaks by FTIR spectrometry.
In FTIR spectrometry, IR energy from an interferometer irradiates a sample which absorbs some of the energy at different wavelengths. The remaining energy is detected to produce a composite time domain signal called an interferogram. Such signal is digitized and subjected to mathematical analysis including a Fourier transform, to produce an absorption spectrum indicative of the structure and make-up of the sample. By combining this technique with that of liquid chromatography, the FTIR method provides further information about the molecular character of each eluting peak.
When such techniques are combined, it is desirable to analyze the eluting peaks on a real time basis, i.e., as the flow from the LC. But this objective is difficult to achieve primarily because of the presence of a large amount or excess of solvent in the effluent. Generally, the excess solvent must be removed in order to provide an accurate analysis.
Another general characteristic of prior art techniques is that the effluent from the LC, after passing through a detector, is normally collected in a waste receptacle and disposed of. The investigator cannot at a later time go back and test the original sample but would have to repeat the experiment and hope that the results reproduce the original measurements.
A technique called "thermospraying" was also developed in the prior art for removing excess amounts of solvent from the effluent from an LC and directing the remainder, including any eluting peaks or components, into a mass spectrometer where the components are ionized and analyzed. This technique is described in "Liquid Chromatograph - Mass Spectrometer for Analysis of Non-Volatile Samples" by C. R. Blakely, J. J. Carmody, and M. L. Vestal, Anal. Chem., 1980, Vol. 52, pages 1636-1641. The liquid flowing from the LC is passed through a flash vaporizer in which about 95% of the liquid is vaporized while the remainder, including the non-volatile sample components, are directed as a collimated particle or aerosol beam moving at a rapid velocity, into the mass spectrometer for ionization and analysis. As described in the article, the vaporizer is an oxy-hydrogen torch through which the effluent passes. Subsequently, an electrically heated nozzle was developed to replace the torch.
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