Table 3.

Experimental conditions and results from 2ⁿ full factorial design for acid, alkali, oxidative, and thermal degradation.

	Experimental conditions			Acid degradation			Alkali degradation			Oxidative degradation			Experimental conditions		Thermal degradation
Exp. No	Factor levels						Responses (%)						Factor levels		Responses (%)
	x 1	x 2	x 3	y 1	y 2	y 3	y 1	y 2	y 3	y 1	y 2	y 3	x 4	x 5	y 1	y 2	y 3
1.	-	-	-	7.32	0.15	6.83	15.28	0.17	11.23	1.09	0.03	0.12	-	-	3.98	0.04	3.38
2.	+	-	-	14.43	0.12	13.93	16.23	0.10	12.53	1.16	0.04	0.13	-	+	6.33	0.09	5.38
3.	-	+	-	5.79	0.25	5.04	26.65	0.12	15.23	1.45	0.06	0.14	+	-	20.12	0.26	17.10
4.	+	+	-	22.04	0.17	21.74	39.43	0.08	23.50	1.55	0.08	0.16	+	+	25.79	0.28	21.92
5.	-	-	+	16.71	0.05	16.39	37.25	0.09	35.89	2.19	0.10	2.04
6.	+	-	+	41.05	0.09	40.73	48.32	0.15	40.23	3.29	0.17	2.16
7.	-	+	+	18.76	0.23	18.47	58.23	0.11	45.62	4.79	0.15	2.56
8.	+	+	+	39.89	0.29	38.32	68.89	0.19	58.26	6.28	0.19	2.89

x ₁: stressor strength 0.01 M and 0.1 M HCl/NaOH or 3% and 30% H₂O₂ for hydrolysis and oxidative degradation respectable; x₂: temperature 25°C and 40°C; x₃: time 15 and 45 minutes; x₄: temperature: 80°C and 105°C; x₅: time 180 and 300 minutes; y₁: amount of total impurities (%);y₂: amount of impurity with RRT 1.16 (%); and y₃: amount of impurity A (%). The high level of each factor was considered as “+" and low level as “−".