Rapid Characterization of Tanshinone Extract Powder by Near Infrared Spectroscopy

Table 1

Factors and levels of central composite design ().

Name	Units	Low	High		+
Ethanol concentration	%	80	100	80	100
Ethanol volume	L	4	6	4	6
Decoction time	Hour	0.5	3	0.5	3

means the distance between the “star” point and the central point.