Comprehensive Assessment of Degradation Behavior of Simvastatin by UHPLC/MS Method, Employing Experimental Design Methodology

Table 6

Statistical parameters of ANOVA and obtained regression coefficients for different degradation.

	R^2	R^2 Predicted	R^2 Adjusted	Adequate precision	Regression coefficients
					Acid degradation
	0.9736	0.8943	0.9537	16.724	20.75	8.60	/	8.35	/	/	2.76	/
	0.9823	0.9293	0.9691	23.526	0.17	/	0.066	/	/	0.029	0.026	/
	0.9701	0.8806	0.9477	15.756	20.21	8.53	/	8.33	/	/	2.53	/
Alkali degradation
	0.9810	0.9241	0.9668	22.878	38.79	4.43	9.51	14.39	/	/	/	/
	0.9590	0.8362	0.9283	15.000	0.13	/	/	8.7E^−3		0.016	0.031	/
	0.9730	0.8920	0.9527	17.544	30.31	3.32	5.34	14.69	/	/	/	/
Oxidative degradation
	0.9328	0.7312	0.8824	9.504	2.73	/	0.79	1.41	/	0.61	/	/
	0.9595	0.8382	0.9292	14.839	0.10	0.017	0.017	0.050	/	/	/	/
	0.9943	0.9771	0.9900	29.558	1.28	/	0.16	1.14	/	0.15	/	/
Thermal degradation
	0.9439	0.7755	0.9158	8.203	14.05	8.90	/	/	/	/	/	/
	0.9918	0.9672	0.9877	22.000	0.16	0.11	/	/	/	/	/	/
	0.9383	0.7531	0.9074	7.797	12.06	7.45	/	/	/	/	/	/

Linear mathematical model of the measured response ,
where is the response [: amount of total impurities (%); : amount of impurity with RRT 1.16 (%); : amount of Simvastatin impurity A (%)], is investigated factors [for acid, alkali, and oxidative degradation; represents stressor strength (0.01 M and 0.1 M HCl/NaOH or 3% and 30% H₂O₂ for hydrolysis and oxidative degradation respectable); represents temperature and represents time of exposure. For thermal degradation is temperature and is time of exposure]; is the intercept , and , , , , and as regression coefficients for the variables and interaction between the variables.