The ratio peaks depicted in figure 33 clearly indicate the presence of an impurity by the sloping top of the anthracene peak. This is further confirmed by the difference in the spectra for the leading and trailing edges of the peak.

Figure 33  Curves Relating the Adsorption Ratio, ,  and Time

Spectra taken at the leading and trailing edge of the anthracene peak are shown superimposed in figure 34. Further work identified the impurity as t-butyl benzene at a level of about 5%.

Figure 34  Superimposed Spectra Taken at the Leading and Trailing Edges of the Anthracene Peak

Another example of the use of the diode array detector to demonstrate peak purity is shown in figure 35.