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  • 1 Quinta Analytica
  • 1 Quinta Analytica
  • 1 Quinta Analytica
  • 1 Quinta Analytica

Analytical Research and Development

 

Structure elucidation of synthetic and degradation impurities

An identification and structural elucidation of impurities represents a frequent task which we deal with. All unknown impurities present at levels higher than allowed by legislation (usually 0.1 %) mean complications for a customer, as they may attract unwelcome attention during a registration procedure.

 It is always an advantage to know the structure of impurities when you need to distinguish those originating in a synthesis, from those originating from a subsequent degradation of the compound. The former ones can be controlled, for instance, by tuning the manufacturing process. Whereas the later can be directly synthesized when you know what they are similar to. Then, for instance, some toxicological data can be gathered and consequently the specification limit can be raised.

 Nowadays, mass spectrometry is extensively used for the structural elucidation. MS can be coupled to gas (GC/MS) or a liquid chromatography (LC/MS).

When the unknown impurity is volatile we successfully use our single-quad GC/MS system. Through the electron impact (EI) ionization, it provides sufficient information leading to the final structure. Usually, the digital mass spectral library (NIST) is successfully employed here.

 Long-term experience has showed that for a structural determination of the vast majority of non-volatile organic impurities, LC/MS with ESI and APCI ionization is the best choice. Our LC/MS system LTQ (Thermo-Finnigan) is equipped with a linear ion trap, combining advantages of a classic ion trap (with MSn capabilities and high scanning speed) with a quadrupole (and its high sensitivity). Moreover, the LTQ ion source interface is designed in an orthogonal fashion, providing higher resistance against contamination by sample matrices or partly non-volatile buffers.

If LC/MS appears not to be sufficient enough, we are able to isolate the impurity of interest with the help of preparative liquid chromatography and subsequently coordinated, for example, NMR measurement. We are skilled in interpretation of resulting NMR spectra so that confidential data will not be breached.