2010 TRI/PRINCETON CONFERENCE 195 The corresponding spectra for virgin and bleached Piedmont hair are provided in Figure 3. A numerical summary of these data is provided in Table I. Here, we clearly see an in- crease in Trp fl uorescence as a result of bleaching, both in the case of dark brown and Piedmont hair. We also see a large increase in the fl uorescence of the principal kynurenine peak. The fl uorescence signal of Trp increases only slightly for dark brown hair as com- pared to an almost two-fold increase in Piedmont hair. The principal kynurenine peak, on the other hand, more than doubles for dark brown hair and increases by one-half for Pied- mont hair. The peak intensity at the extreme of the spectra remains the same for Pied- mont hair. It is interesting to examine the changes in the ratio of ITrp/IKyn and I509/ IKyn. Bleaching results in a decrease in ITrp/IKyn for dark brown hair and an increase in this same ratio for Piedmont hair. Curiously, the ratio of the peak at the longest excitation Figure 2. Excitation-emission matrices of (A) virgin and (B) bleached dark brown hair.

JOURNAL OF COSMETIC SCIENCE 196 band to the kynurenine peak, I509/IKyn, decreases as a result of bleaching in Piedmont hair, even though the peak intensity increases. The decrease in this ratio parallels the loss of yellow pigmentation in Piedmont hair, something we also observed in photo-damaged Piedmont hair (see section below). In the case of dark brown hair, I509 increases dramat- ically resulting in a very large increase in I509/IKyn. Some of the fl uorescence increase at I509 could be due to the formation of degradation products however, the large increase can most likely be attributed to decreased quantities of melanin. Since bleaching changes the pigmentation characteristics of the fi ber, it will also have pro- found effects on the fi ber’s fl uorescence. In the case of dark brown hair, a decrease in the quantity of Trp relative to the kynurenines could indicate that any one (or a combination) of the following processes occur: Trp is degraded, kynurenines are formed as a result of Trp degradation, or melanin impedes kynurenine fl uorescence more than Trp fl uorescence. In Figure 3. Excitation-emission matrices of (A) virgin and (B) bleached Piedmont hair.