Detection of the iron complexes with hydrolysis products of cephalexin and cefradine upon high-performance liquid chromatography/electrospray ionization mass spectrometry analysis

RationaleCephalosporins (e.g. cephalexin, cefradine) are a major group of widely used -lactam antibiotics. Hydrolysis of the -lactam ring is an important reaction (often undesired) which leads to deactivation of -lactams. To the best of our knowledge there is no electrospray ionization mass spectrometry (ESI-MS) data reported concerning the products of hydrolysis of cephalosporins. MethodsThe hydrolysis of cephalexin and cefradine was performed in aqueous NaOH solutions. After the process the solutions were analyzed by high-performance liquid chromatography (HPLC)/ESI-MS. The elemental compositions of the ions discussed were confirmed by the accurate mass measurements on a quadrupole time-of-flight (QTOF) mass spectrometer. ResultsUnexpectedly, complexes between the hydrolysis products of cephalexin and cefradine (CFLh and CFRh) and iron cation were detected upon HPLC/ESI-MS analysis, namely the ions [(CFLh-H)(2)+Fe](+) and [(CFRh-H)(2)+Fe](+), although iron was not added to the analyzed solutions or to the mobile phase. These ions were found to be very stable in the gas phase. ConclusionsThe detection of the complexes between the hydrolysis products of cephalosporins and iron may have a positive impact on the sensitivity and specificity of HPLC/ESI-MS analyses of the hydrolysis products of some cephalosporins.