-Prochlorparazln* -Fluphsnazina

Perphenazine Trifluoperazine

Time (minutes) Sunlight - Glass Ampoule o -0.6

Time (minutes) Sunlight - Glass Ampoule

Time (days) Fluorescent/Diffuse Light- Glass Ampoule

Figure 3. Degradation profdes of prochloperazine, perphenazine, trifluoperazine and fluphenazine

The order of degradation (phenothiazine % remaining) on exposure to the 30W UV source and sunlight at t Vi is from the most to the least stable: trifluoperazine (46.88/39.54), fluphenazine (40.55/41.77), prochlorperazine (30.04/26.23) and perphenazine (19.70/14.11). Irradiation under fluorescent/diffuse light further highlights the instability of perphenazine with 59% degradation occurring after 16 days while for the remaining three derivatives the degradation ranged between 40-50%

The degradation of these compounds displayed first-order kinetics with the pseudo firstorder rate constants determined from the slopes of the linear plots (Figure 3) and correlation coefficients for these apparent first-order kinetic reactions are presented in Table 2.

Table 2 First-order rate constants (correlation coefficients)


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