Page 326 - Tandem Techniques

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localized masses of solutes are located round the perimeter of the disk in the form of a 'physical'
chromatogram. After the separation is complete, the disk is removed and placed on the stage of the
optical module, which is located in the sample compartment of the FTIR bench. The compartment is
purged with carbon dioxide-free air. The stage rotates and the incoming IR beam passes though the
sample, and the spectrum is obtained by reflected transmission. As already discussed, this procedure
produces a two-pass transmission spectrum of the sample. As the disk is rotated and the spectra
obtained, they are stored and so the spectrum of any particular peak can be recalled and printed out as
desired. In addition the individual spectra can be integrated and the results plotted against time to
produce a chromatogram of the separation. The FTIR spectra obtained from the analysis of an oil-based
steroid solution used for intravenous injection containing benzyl benzoate and testosterone cypionate
are shown in Figure 8.16.

Figure 8.16
IR Spectra of Benzyl Benzoate and Testosterone
Cypionate Obtained from the LC/IR Interface
Courtesy of Lab Connections Inc.

A sample of the oil (0.5 ml) was mixed with 15 ml of methanol and shaken for 10 minutes. The mixture
was then centrifuged at 1100 g for 5