Page 341 - Tandem Techniques

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the results that were obtained, is shown in the three dimensional chromatogram of the separation
depicted in Figure 8.27.

Figure 8.27
A Three-dimensional Chromatogram Obtained from an LC/RAMAN
Tandem Instrument Separating Three Purine Bases.
Reprinted with permission from R. Sheng, F. Ni and T. M. Cotton,
Anal. Chem., 63(5)(1991)437, Copyright 1991 American Chemical Society

It is seen that a good separation is obtained, although it is difficult to determine exactly the extent to
which the separation was degraded in the interface. In any event, it appears to be relatively little, and
considering that this type of instrument is still in the relatively early stages of development, these
results bode well for the future of this particular tandem technique.

In the past, tandem systems involving the combination of the liquid chromatograph in-line with the
infrared spectrometer have not performed well. Most IR spectra of LC eluents have been obtained by
what are, in effect, off-line procedures. This is apparent from the many examples given in this chapter.
This lack of interest has largely arisen from the poor sensitivity of the early instruments, and also,
perhaps, from the clumsy