ESI-MS studies of mixed-ligand Fe(II) complexes containing 1,10-phenanthroline and 1,10-phenanthroline-5,6-dione as ligands.

In order to monitor the progression of the synthesis and the separation of novel mixed-ligand iron complexes containing 1,10-phenanthroline, 1,10-phenanthroline-5,6-dione, and NCS- as ligands all products were mass analyzed by electrospray ionization ion trap MS/MS. The spectra of methanol (MeOH), acetonitrile (ACN), water, and ethanol (EtOH) solutions were collected and the results were compared. It was detected under applied electrospray ionization mass spectrometry (ESI-MS) conditions that MeOH, water, and EtOH formed solvent clusters around the free or complexed 1,10-phenanthroline-5,6-dione.

Ionization, lipophilicity and solubility properties of repaglinide.

Potentiometric and spectrophotometric titrations were used for the determination of ionization behaviour, lipophilicity and solubility profile of repaglinide. Acid-base equilibria were characterized by means of protonation macro- and microconstants using Target Factor Analysis of spectrophotometric data. Lipophilicity profiles were evaluated by determination of partition coefficients of neutral and ionized forms of repaglinide in biphasic octanol/water system.

The application of LC-NMR and LC-MS for the separation and rapid structure elucidation of an unknown impurity in 5-aminosalicylic acid.

This work has demonstrated the usefulness of combining liquid chromatography-nuclear magnetic resonance spectroscopy (LC-NMR) and liquid chromatography-mass spectrometry (LC-MS) methodologies for a rapid identification of an unknown impurity (N1) in the drug 5-aminosalycilic acid. Complementary information obtained from the two methods has revealed plenty of structural information and led to the fast on-line structure determination of N1 prior to its isolation and purification. The analysis of LC-NMR and LC-MS spectra revealed that N1 and 5-aminosalycilic acid are structurally closely related compounds.