Stability Indicating RP-HPLC Method for Simultaneous Determination of Pholcodine and Guaiacol in Pharmaceutical Syrup

Abstract

Guaiacol (GUA) and pholcodine (PHO) were simultaneously determined in a pharmaceutical syrup using RP-HPLC with UV detection. The separation was performed using X-Bridge C8 column (100 mm × 4.6 mm, 2.5 μm particle size) and a mobile phase of acetonitrile – phosphate buffer (pH 6.8; 50 mM) (25:75, v/v) at a flow rate of 0.55 mL/min. The column temperature was adjusted to 35°C, and the detector was set to measure the absorbance at 238 nm. The ICH guidelines were followed to validate the method. The linearity was studied over 6.0 – 70 μg/mL and 4 – 420 μg/mL ranges for GUA and PHO, respectively. Linear relationships were obtained over the specified concentration ranges with correlation coefficients of 0.9989 for GUA and 0.9999 for PHO. The limits of detection were also determined and found to be 2 μg/mL for GUA and 1.2 μg/mL for PHO. The proposed method was applied for the determination of both drugs in Coughpent syrup; the results comply with the label claim (0.1572g/120mL for PHO and 0.0237g/120mL for GUA).