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The objective of this research was to study the effect of pH on the photodegradation of aqueous solutions of 5×10–5 M acesulfame-K (λmax, 226 nm;e, 11 400 mol–1 L cm–1). Photodegradation followed first-order kinetics and was found to be pH-dependent. The degradation rate constant was calculated to be 6.7×10–2 min–1, 4.5×10–2 min–1, 3.4×10–2 min–1 and 17.4×10–2 min–1, respectively, at pH 3, pH 9 and pH 12.

Photodegradation of 2.6 x 10(-5) M aqueous solutions of sodium usnate at various pH was studied. Photodegradation appeared to follow first-order kinetics and was found to be pH dependent. The degradation rate constant was calculated to be 9.20 x 10(-4) min-1, 5.93 x 10(-4) min-1, 9.69 x 10(-4) min-1, and 9.88 x 10(-4) min-1 at pH 6, pH 7, pH 8, and pH 9, respectively.

The objective of this research is to evaluate the thermal stability of monoammonium glycyrrhizinate. Thermodegradation of solutions of monoammonium glycyrrhizinate at various temperatures (50, 70 and 90 degrees C) was studied. This degradation appeared to follow first-order kinetics independently of temperature and was found to be pH dependent. The experiments revealed an activation energy (Ea) of about 33 kJ mol-1 and a t 90% of about 3 years at 20 degrees C in a pH range from 7 to 9. So it can be concluded that monoammonium glycyrrhizinate is stable in a pH range from 7 to 9. It can be interesting for use in oral care or in food industry.

The objective of this research is to evaluate the stability of climbazol. Thermodegradation of solutions of climbazol at various temperatures (50, 70 and 90°C) was studied. This degradation appeared to follow first-order kinetics whatever the temperature. The experiments revealed an activation energy Ea of 5.4 kcal mol−1 and a time necessary to obtain a decrease of 10% of the initial concentration, t90%, of 81.9 days for climbazol in aqueous diluted solution at 20°C.

The objecti ve of this work was the evaluation of neohesperidin dihydrochalcone thermostability. For this acceler ated stability stud y, we ha ve used an isothermal method at three temper atures (50, 70 and 90 °C). The thermodegradation of aqueous diluted solutions of neohesperidin dihydrochalcone at various pH was studied . This degradation appeared to follow first-order kinetics and was found to be pH-dependent. In the best stability conditions (pH = 4.50), the experiments revealed an acti vation energy ( Ea) of 45.8 kJ mol -1 and a t90% of 164 days, at 20 °C.

The objective of this study is the evaluation of sodium usnate thermostability. To this end, we used an isothermal method at four temperatures (40, 50, 60, and 70°C). The themodegradation of dilute aqueous solutions of sodium usnate was studied at various pH values. This degradation appeared to follow first-order kinetics. Under the best stability conditions (pH = 8), the experiments gave a t 90% of 54.58 days, and a t 50% of 359.07 days at 20°C

The authors studied the effects of temperature on the stability of thaumatin in aqueous diluted solutions at 50, 70 and 90°C. The thermodegradation follows first-order kinetics and is pH-dependent. At 20°C and pH 2, the time ( t 90% ) necessary to obtain a decrease of 10% of the initial concentration estimated by extrapolation is 43 days for thaumatin at a concentration of 1.90 × 10 –5 M. Thaumatin is most stable at pH 2.