LC-MS/MS and LC-UV Determination of Moniliformin by Adding Lanthanide Ions to the Mobile Phase

An innovative chromatographic analysis was developed for the determination of\r\nmoniliformin (MON). Because of its ionic nature, MON is weakly retained in reversed-phase\r\nchromatography and the separation may be tricky. Nevertheless, this technique is normally used\r\neither with the formation of ion pairs or employing specific RP columns for polar compounds, or\r\ncombining anion exchange and hydrophobic interactions. Hydrophilic interaction chromatography\r\n(HILIC) was also used, but a non-negligible peak tailing was observed. Besides its ionic nature, MON\r\nis a di-ketone and di-ketones, mainly -di-ketones, can easily form complexes with lanthanide ions.\r\nThen, in this work the addition of lanthanide ions to the mobile phase was investigated, aiming at\r\nimproving peak shape and MON separation. La3+, Tb3+ or Eu3+ aqueous solutions were used as\r\nmobile phase and MON was chromatographed using a LC-NH2 column. The probable formation of\r\ncoordination complexes lanthanide-MON in the HPLC mobile phase allowed to obtain a symmetrical\r\npeak shape and a satisfactory chromatographic separation by both mass spectrometry (MS/MS) and\r\nUV detection. Finally, a suitable extraction and purification method for MON determination in cereal\r\nsamples was developed.