A Simple and Improved HPLC-PDA Method for Simultaneous Estimation of Fexofenadine and Pseudoephedrine in Extended Release Tablets by Response Surface Methodology

Table 2

Independent variables (factor) and responses investigated in CCD design.

Independent variables (factors)	Levels of factors			Dependent variables; (responses)	Target of optimization
	High (+)	Medium (0)	Low (−)
Methanol (% v/v)	15	10	5	Retention of PSU	≤ 3 min
Acetonitrile (% v/v)	60	40	20	Retention of FEX	3.5 min ≤ ≤ 8 min
Buffer (% v/v)	Quantity sufficient to 100%			Resolution ()	6% ≤ ≤ 15%