TLC-TOF SIMS monitoring of zinc complex origin -: Carboxylate ligand movement

To characterize the stability and retention behavior of zinc carboxylato mixed-ligand complexes movement of the carboxylate ligand has been monitored by thin-layer chromatography coupled with time-of-flight secondary-ion mass spectrometry (TLC-TOF SIMS). Chromatography was performed on aluminum-backed RP-18 layers with a methanol-water mobile phase. After development the layers were coated with silver, from the vapor state, and the analytes were then eluted with a strongly polar mobile phase to a target channel. Analytes on targets defined by average R-F values were analyzed by TOF SIMS. From preliminary analyses it was found that only zinc carboxylate complexes containing butyrate or isobutyrate anions as ligands could be detected and identified by TOF SIMS (m/z 43, butyl, and m/z 87, butyrate). Further analysis was performed on the Zn(CH3CH2COO)(2)(tu)(2) complex only. It was found that butyrate anion moves in a spread chromatographic zone from the start of the layer. The maximum concentration of the carboxylate ligand was found at R-F 0.33. From this position the intensity of the ions mentioned above decreases rapidly. This result confirms that the butyrate ligand of the Zn complex moves independently on an auxiliary (organic) ligand (thiourea) and partially on the zinc cation, confirming that the complex decomposes during chromatography.