Perfusion calorimetry in the characterization of solvates forming isomorphic desolvates.

In this study, the potential of perfusion calorimetry in the characterization of solvates forming isomorphic desolvates was investigated. Perfusion calorimetry was used to expose different hydrates forming isomorphic desolvates (emodepside hydrates II-IV, erythromycin A dihydrate and spirapril hydrochloride monohydrate) to stepwise increasing relative vapour pressures (RVP) of water and methanol, respectively, while measuring thermal activity. Furthermore, the suitability of perfusion calorimetry to distinguish the transformation of a desolvate into an isomorphic solvate from the adsorption of solvent molecules to crystal surfaces as well as from solvate formation that is accompanied by structural rearrangement was investigated.

International GLP: a critical reflection on the harmonized global GLP standard from a test facility viewpoint.

The implementation of the Organisation for Economic Co-operation and Development (OEC D) principles of good laboratory practice (GLP) on an international level is well advanced. However, the OEC D GLP guidelines as well as the corresponding national GLP regulations leave room for interpretation. As a consequence, working in parallel in GLP environments in several countries represents a challenge.

Isotope dilution GC-MS of benzylpenicillin residues in bovine muscle.

The German provisional prevalidated official method for the determination of residues of benzylpenicillin in muscle (beef) which uses gas chromatography with nitrogen-specific detection (GC-NPD) was successfully adapted to gas chromatography-mass spectrometry (GC-MS) with selected-ion monitoring. The programmed temperature vaporisation injection technique used in the original method was substituted by on-column injection. An isotope dilution procedure for benzylpenicillin using 13C2-labelled benzylpenicillin as internal standard was developed to improve the reliability of the GC-MS results.

Development of a gas chromatography-mass spectrometry method for the analysis of aminoglycoside antibiotics using experimental design for the optimisation of the derivatisation reactions.

A packed column GC-electron-capture detection method for the analysis of the aminoglycoside antibiotics kanamycin and gentamicin was adapted to capillary GC-MS. The analytes were derivatised using a two-step procedure involving trimethylsilylation of the hydroxyl groups with trimethylsilylimidazole and acylation of the amino groups with heptafluorobutyrylimidazole. Electron impact mass spectra of the resulting derivatives of kanamycin A and gentamicins C1, C1a and C2 are given and interpreted.