[Zurück]

E. Rosenberg:
"On the Potential and Pitfalls of Building LC-MS Spectral Libraries for Natural Organic Dyestuffs";
Poster: HPLC 2009 - 34th International Symposium on High-Performance Liquid Phase Separations and Related Techniques, Dresden, Germany; 28.06.2009 - 02.07.2009.

Liquid chromatography-mass spectrometry has become one of the prime techniques for the characterisation of natural organic substances. The separation power of liquid chromatography, coupled with the sensitive and selective detection capability of mass spectrometry form a most versatile hyphenation, which is particularly useful in the quantitation and identification of natural organic substances. When using single quadrupole or ion trap mass spectrometers, however, tentative identification is always based on the chromatographic information combined with mass spectral information, confirming or disproving the identity of an analyte based on the expected mass signals.
The positive identification of unknowns based merely on their mass spectrum is rarely possible due to the lack of informative signals in the mass spectrum obtained by simple spectrometers with soft ionisation techniques.
There are three general ways to increase the information content of mass spectrometric detection: first, by using in source-collision induced dissociation with single mass spectrometers; second, by using triple-quadrupole or ion trap mass spectrometers to generate MS/MS or MSn spectra, also achievable with other types of hybrid instruments; and third, to measure exact masses with high resolution mass spectrometers. The additional information provided by these techniques over MS detection with simple mass spectrometers under mild ionisation conditions can be used to identify unknown substances, and to build spectral libraries for a limited set of compounds. Similar approaches have already been reported for pesticide analysis [1] and forensic analysis [2], but not yet so far for the analysis of natural substances.
Using the analysis of natural organic dyestuffs as an example which is of particular interest in the analysis of artistic and historic objects [3], we will discuss what practical approaches can be taken to overcome the current limitations of building mass spectral libraries, and to produce mass spectra which are richer in information than typically encountered when using standard acquisition parameters. With this higher degree of information, even obtainable on single quadrupole (or ion trap) MS instruments, spectra can be recorded that, after appropriate processing can be used to create spectral libraries that are searchable. This development, illustrated by some representative examples, will further increase the usefulness of LC-MS in the characterisation of natural organic dyestuffs.


[1] M.E. Thurman, I. Ferrer, O. Malato, A.R. Fernández-Alba, Food Additives Contam. 23 (2006) 1169-1178.
[2] H.H. Maurer, J. Mass Spectrom. 41 (2006) 1399-1413.
[3] E. Rosenberg, Anal. Bioanal. Chem. 391 (2008) 33-57.