Info

* Figures are approximate as degradation depends on particle size and area of exposure.

* Figures are approximate as degradation depends on particle size and area of exposure.

3.1 Analytical Study of D├ęgradants from Light Stressing in Solid-State

The most striking result in Table 2 is the dramatic loss of area for compound (2) form I by comparison with the other solids measured. The reverse phase HPLC impurity profile shows that this form degrades principally to a single compound which has been identified by NMR, MS and X-ray crystallography as the cyclobutane dimer, (4) shown in Figure 3. This dimer is akin to an analogous dimer formed by light irradiation of cinnamic acid and its derivatives.6

Figure 3 The structure of (4), the product of irradiated (2) form I.

The degradation of compound (3) in the solid state is also well explained by the HPLC data. In this case the loss in area may be accounted for by a large envelope of peaks observed in the chromatogram. Reverse phase HPLC, however, is unable to account for the losses recorded for compound (1) and compound (2) form II. The degradation products from the irradiation of 1, identified by HPLC and HPLC/MS, are given in Figure 4. However, the intensity of these peaks in the HPLC profile (Figure 5) cannot fully account for the assay loss. Complementary CE methods were also unable to show any significant products of degradation.

Figure 4 The degradation products of (1) on exposure to xenon light as deduced by LC/M
0 0

Post a comment