Table 1.

Central composite design and response.

No.	X1 (oil phase mass percentage; %)	X2 (Km)	Y1 (grain size; nm)	Y2 (drug-containing amount; mg/g)
1	12.93	1.15	27.05	1.58
2	12.93	1.85	24.28	2.81
3	27.07	1.15	67.45	1.53
4	27.07	1.85	44.54	2.28
5	10	1.5	22.31	0.82
6	30	1.5	67.57	2.88
7	20	1	39.12	1.00
8	20	2	33.54	1.45
9	20	1.5	33.71	1.33
10	20	1.5	33.43	1.27
11	20	1.5	35.22	1.31
12	20	1.5	35.22	1.28
13	20	1.5	35.43	1.24