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.