Simultaneous estimation of phenylpropanolamine HCl, guaiphenesin and diphenylpyraline HCl in syrups by LC.

A simple, precise and accurate HPLC method was developed for the simultaneous estimation of phenyl-propanolamine HCl, guaiphenesin and diphenylpyraline HCl in syrup. The method was carried out on a Shimpak C8 column with a mobile phase consisting of acetonitrile-triethylamine (pH adjusted to 3.5 using orthophosphoric acid; 0.5%), (35:65, v/v) at a flow rate of 1.2 ml min(-1). Detection was carried out at 210 nm. Diphenhydramine was used as internal standard. The validation of the method was also carried out.