Objective To establish an HPLC method for simultaneous assaying of
amoxicillin sodium and
flucloxacillin sodium for injection
and their related substances.Method Ion-pairs along with gradient elution HPLC method was proposed.The separation was performed on an HP Zorbax Elicpse XDB-C8 column (4.6mm×150mm);The mobile phase A composed of 0.01mol/L KH2PO4 buffer solution (pH 6.5) containing 1.4%cetyl trimethyl ammonium bromide∶acetonitrile (70∶30);mobile phase B composed of 0.01mol/L KH2PO4 buffer solution (pH6.5) containing 1.4%cetyl trimethyl ammonium bromide∶acetonitrile(30∶70).The detection was carried out on a UV detector at 254nm;at a flow rate is about 1ml/min by gradient elution.Results Under the chromatographic system described above
amoxicillin and
flucloxacillin all have acceptable responses at this wavelength with suitable chromatographic retention on the column.The main impurities of the product for injection were all separated successsively under the gradient elution system;When the injection volume was 10μl,the standard curves of amoxicillin and flucloxacillin were all linear in the range of 0.0088～2.210mg/ml (r=0.99999,n=10) and of 0.0097～2.430 mg/ml(r=0.99997,n=10) respectively.The RSD for repetition was 1.3%and 0.6%,and the average recovery rate of amoxicillin and flucloxacillin was 100.27%and 100.54%respectively (n=9).Conclusion This method offered a rapid,repeatable and accurate procedure convenient for assaying amoxicillin and flucloxacillin simultaneously as well as for determining their impurities.