Table 7. Robustness Conditions and Plackett–Burman Experimental Design Conditions.

	Level
Parameters	Low (−)	Real	High (+)
Wavelength (nm)	212	214	216
Column temperature (°C)	24.2	25	25.8
Flow r(mL/min)	0.38	0.39	0.40
pH Value of mobile phase	2.3	2.4	2.5

Conditions
Injection	Wavelength (nm)	Column Temperature (°C)	Flow Rate (mL/min)	pH Value of Mobile Phase
1	+	+	–	+
2	+	–	–	–
3	–	+	–	+
4	–	+	+	–
5	–	–	+	–
6	+	+	–	–
7	–	+	+	+
8	+	–	+	+
9	+	+	+	–
10	–	–	–	–
11	+	–	+	+
12	–	–	–	+