Validation of a high-performance liquid chromatographic method for the simultaneous determination of tramadol and its impurities in oral drops as a pharmaceutical formulation

The novel, rapid high performance liquid chromatographic method for the determination of tramadol hydrochloride and its three impurities was developed and validated. The method can simultaneously assay potassium sorbate, used as preservative, and saccharin sodium, used as sweetener in tramadol pharmaceutical formulation. The separation was carried out on a C18 XTerra™ (150 mm × 4.6 mm, 5 mm) column using acetonitrile—0.015 M Na2HPO4 buffer (2:8, v/v) as mobile phase (pH value 3.0 was adjusted with orthophosphoric acid) at a flow rate 1.0 ml min−1, temperature of the column 20 °C and UV detection at 218 nm. The method was found to be linear (r > 0.999) in the range of 0.05–0.8 mg ml−1 for tramadol hydrochloride, 0.1–1.2 mg ml−1 for impurities B and C and for impurity A (r > 0.995) in the range 0.15–2.4 mg ml−1. The low RSD values indicate good precision and high recovery values indicate excellent accuracy of the HPLC method. Developed method was successfully applied to the determination of tramadol hydrochloride, its investigated impurities and potassium sorbate in commercial formulation. The recovery of tramadol hydrochloride was 98.25% and RSD was 1.80%. The method is rapid and sensitive enough to be used to analyse Trodon® oral drops.