Determination of elemental impurities in lomefloxacin hydrochloride ear drops by ICP-MS Using Oxygen Reaction Mode and study of their catalytic effect on photodegradation reaction.

Abstract

According to the requirements of ICH Q3D, a method for simultaneous determination of 12 element impurities in lomefloxacin hydrochloride ear drops by inductively coupled plasma mass spectrometry (ICP-MS) was established. However, this product contains high concentrations of organic compounds such as glycerol and ethanol, and there will be interference of soluble carbon when it is determined by direct injection method. Therefore, we applied ICP-MS using oxygen reaction mode to reduce the effect of high organic matter on plasma body. The catalytic effect of trace metal ions on the photodegradation of lomefloxacin hydrochloride was also investigated. The sample was dissolved, diluted and directly determined by direct injection using oxygen reaction mode of ICP-MS with 45 Sc, 73 Ge and 115 In as the internal standards. The direct injection using oxygen reaction mode was equipped with argon-oxygen mixer. To investigate the catalytic effect of metal ions on photodegradation, a series of combinations of lomefloxacin hydrochloride mixed with different metal ions were designed. After being irradiated under ultraviolet light for 10 days, the photodegradation impurities in combinations were determined by HPLC. The linear relationships in the corresponding concentration range for 12 element impurities were good (r>0.9993). Limits of detection were between 0.002~1.294 ng·mL-1 . The average recoveries were 93.7%-108.2%, and the precision RSD were 0.04% ~ 0.55% (n=6). The experimental results showed that metal ions had a certain catalytic effect on photodegradation of lomefloxacin when EDTA, Mg2+ and Cu2+ coexisted. The ICP-MS using oxygen reaction mode is suitable to direct determination of the sample rich in organic matter without digestion, can effectively eliminate the interference of high organic matter in this product. The established method was rapid, sensitive, accurate, and can be used for the quality control of elemental impurities in lomefloxacin hydrochloride ear drops.