NIST20 Mass Spectral Library

The largest increase in coverage to date.

The NIST20 mass spectral libraries are a fully evaluated collection of electron ionization (El) and MS/MS mass spectra, with both chemical and GC data, the package includes software to search and identify unknown spectra.

NIST20 comes with a range of new features of the program and database

Major expansion of coverage of analytically important compounds of all classes, based on documented importance of each compound.
- 350,643 EI spectra for 306,869 compounds (40K increase)
- Four Tandem (MS/MS) libraries with 1,320,389 spectra of 185,608 ions for 30,999 compounds (>2x increase)
- GC Methods/Retention Indices library with 139,963 compounds; 112,253 compounds in the Main library have retention index data.
For the first time, almost all spectra measured and fully evaluated at NIST.
Modernized and enhanced evaluation procedure allowing for multiple evaluations of spectra.
Enhanced comparison of replicate spectra and ‘best of replicates’ selection. The entire library is now based on chemical structures using the NIST-developed InChI Key representation.
Enhanced quality control using greatly improved MS Interpreter program that links ions to originating structures in the precursor molecule.
Enhanced method for assisting the examination of results that has many spectra generated by Tandem spectra.

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NIST Tandem Mass Spectral Library, 2020 release

Fragmentation methods

27,840 HRAM (high res accurate mass) compounds
29,890 QTOF, HCD, IT-HRAM, QqQ compounds
29,444 ion trap compounds (low rep., up to MS⁴)
246 APCI HRAM “extractablees and leachables”

Precursor ion types

26,575 protonated
12,589 deprotonated
10,032 water/ammonia loss
34,199 other in-source generated

Wide variety of compounds

Marbofloxacin antibiotic
Naphthalene E&L, APCI
Luteolin glucoside flavone

Retinoic acid metabolite
Fuc-GM1(d18:1/16:0) glycolipid
and more

Hybrid Search to allow for identification of compounds not in the library

The novel hybrid search method can help identify compounds not in the library by similarity to compounds that are. It’s called “hybrid” searching because it combines conventional, direct peak matching with the logical equivalent of neutral-loss matching.

A successful hybrid search requires the library to contain “cognates” of the unknown: similar compounds with a structural difference confined to a single region of the molecule, that does not substantially alter its fragmentation behavior. Peaks shifted in the ‘Hybrid Search’ are shown before and also after shifting.