Simultaneous Assay of Dexchlorpheniramine Maleate, Betamethasone, and Sodium Benzoate in Syrup by a Reliable and Robust HPLC Method
Table 1
Results of preliminary optimization.
Column
Mobile phase
Elution mode
Flow rate
Observation
Result
Phenomenex C18
Methanol—phosphate buffer 0.02 M pH 2.7 (40 : 60, v : v)
Isocratic
1.0 mL/min
Poor peak shapes for dexchlorpheniramine maleate and sodium benzoate, retention too long for betamethasone (more than 20 minutes), betamethasone still partially coeluted with a matrix peak
Rejected
Phenomenex C18
Acetonitril—phosphate buffer 0.02 M pH 2.7 (40 : 60, v : v)
Isocratic
1.0 mL/min
Better peak shape for dexchlorpheniramine maleate and sodium benzoate, shorter analysis time, but betamethasone still partially coeluted with a matrix peak
Rejected
Phenomenex C18
Acetonitril—acetate buffer 0.025 M pH 3.0 (40 : 60, v : v)
Isocratic
1.0 mL/min
Bethamethasone was resolved from matrix peak but peak shape was poor and peak response unstable
Rejected
Phenomenex C18
Acetonitril—phosphate buffer 0.02 M pH 2.7 (35 : 65, v : v)
Isocratic
1.0 mL/min
Good peak shape for all three analytes and all three analytes were completely separated from matrix components
