Todaylarge mass spectral data bases containing several hundred thousand spectra are commercially available.
For the identification of a mass spectrum from a sample analysiseg a GC-MS runseveral software packages are available that allow to retrieve the most similar spectra from a mass spectral database and to rank the spectra found according to a match quality factor mostly based on visual match of measured and library spectra.
Whereas these algorithms work fine if there is at least one reference spectrum in the database for the sample component under examinationthey often fail to deliver any useful information in the case where no reference spectrum is in the libraryeg in the case of real unknowns.
A search algorithm that does not suffer from this limitation is the SISCOM similarity search used in the MassLib mass spectrometry software. The SISCOM search algorithm is based on the presence of characteristic masses and finds structurally related spectra even if visually similar matches are not available or if spectra are of limited quality which is typical in trace analysis.
MSP Kofel is based in ZollikofenSwitzerzland. www.msp.ch
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