Page 291 - Tandem Techniques

Page 275

any or all of which (despite many spectra being very similar) can be used to confirm the identity of a
compound.

Merely using a single optimum excitation wavelength and monitoring on the complementary optimum
emission wavelength can provide extremely valuable signal enhancement for specific analyses. An
example of this type of selective fluorescence detection is shown in the assay of aflatoxins using
reversed phase chromatography and depicted in Figure 7.15.

Figure 7.15
The Separation of Some Aflatoxins by UV
Absorbance and Fluorescent Emission.
Courtesy of Supelco Inc.(Supplied to
Supelco Inc. by Dr. J. Hurst, Hershey
Foods Corp. Hershey, PA USA.)

A LC 18-reversed phase column was employed with a mobile phase consisting of 20% acetonitrile,
20% methanol and 60% water and a flow rate of 1.1 ml/min. The UV absorbance was monitored at 365
nm and the fluorescence excited at 365 nm and the emission measured at 455 nm. It is seen that
fluorescence response is three to five times greater than that provided by he UV absorbance. However,
as the magnitude of the noise