Medicamentul Veterinar (Nov 2013)
HPLC method for simultaneous determination of oxytocin and clorobutanol in injectable solutions
Abstract
The objective of this work was to establish and validate a HPLC method with UV detection for simultaneous determination of oxytocin and clorobutanol in veterinary injectable formulations. The method is based on European Pharmacopoeia monograph for oxytocin concentrated solution. Chromatographic separation was achieved on a Syn Chropack RP100 C18 column (250 x 4,6mm, 5 μm) with a mobile phase consisting of solutia A: sodium dihydrogen phosphate buffer 0,13 M and solution B: acetonitrile-water (1:1, v/v) with gradient elution (30 % B for 1 min, 30 % B to 60 % B in 30 min, return to initial concentration and echilibration for 15 min before the following injection), at a flowrate of 1 ml/min and detection at 220 nm. The retention times for oxytocin and clorobutanol were about 15 min and 26 min respectively. The degradation products of oxytocin eluted at retention times smaller than 14 min. The resolution between oxytocin and the nearest impurity fulfilled the USP monograph requirements of at least 1,5. The linearity of the method has been settled from 2,5 UI/ml to 20 UI/ml for oxytocin and 1,25 mg/ml to 10 mg/ml for clorobutanol. In these ranges the corelation coefficients were higher than 0,9950. The method allows the separation of oxytocin from degradation products and clorobutanol and could be applicable to quality control of injectable products containing oxytocin and clorobutanol. The method was validated in terms of selectivity, linearity, precision and accuracy.
