Table 2.

Regression coefficient, R², adjusted R², probability values of the response surface models.

Regression coefficient	Partition coefficient (Y1)	Purification factor (Y2)	Yield (Y3 %)
β0	23.33	69.42	97.04
β1	4.50	_	_
β2	3.00	_	33.55
β3	_	4.22	_
β4	_	5.75	14.55
β12	_	_	_
β22	5.61	3.85	46.71
β32	_	_	_
β42	_	1.78	3.76
β12	1.62	_	18.50
β13	_	_	12.34
β14	_	_	14.80
β23	_	_	_
β24	_	8.82	_
β34	_	_	_
R2	0.997	0.993	0.996
R2 (adj.)	0.993	0.991	0.992
Regression(p-value)	0.001 a	0.000 a	0.000 a

β_i: The estimated regression coefficient for the main linear effects. β_ii: The estimated regression coefficient for quadratic effects. β_ij: The estimated regression coefficient for the interaction effects. 1: PEG molecular mass; 2: TLL; 3: NaCl; 4: pH.

^aSignificant (p < 0.05).