The NIST 2014 Mass Spectral Reference Libraries

The U.S. National Institute of Standards and Technology (NIST) has released the NIST 14 mass spectral database, a set of fully evaluated collections of electron impact (EI) mass spectra, tandem MS (MS/MS) mass spectra and retention index (RI) data. It is the
product of a twenty-seven year, comprehensive evaluation and expansion of the world’s most widely used mass spectral reference libraries by a team of experienced mass spectrometrists in which each spectrum was examined for correctness.

The NIST/EPA/NIH Library of Electron Ionization Spectra contains now a total of 242,466 compounds, representing an increase of 29,505 over the prior (2011) version. It also includes 33,782 replicate (alternate) spectra of compounds listed in the main library, an increase of 2,850. New spectra cover a wide range of compound types, with special emphasis given to human and plant metabolites, drugs and compounds of industrial and environmental importance. Thousands of improvements in chemical names, structures and replicate spectra have also been made, including the naming of derivatives.

The NIST Tandem MS Library contains now MS/MS spectra of 9,344 compounds (a 33% increase from 2012 , resp. a 60% increase from the 2011 version). With an increased focus on alternate precursor ions, this has led to an increase in the number of precursor ions by a factor of three relative to the 2012 version with a near doubling of the total number of spectra to 234,284. A large fraction of new spectra were acquired at high accuracy and resolving power, over a range of energies, and in both collision cells (beam type) and ion traps (up to MS4) and, when appropriate, in both positive and negative ion modes. A substantial proportion of these new compounds are human and plant metabolites, drugs, lipids, sugars, peptides, pesticides, surfactants and glycans (the last with structures in ‘cartoon’ format). Advanced noise removal processes have improved the quality of a number of spectra that appeared in earlier versions (as described in X. Yang, P. Neta, S. Stein. “Quality Control for Building Libraries from Electrospray Ionization Tandem Mass Spectra”, Analytical Chemistry, in press).

Also included in the full edition of the NIST 2014 libraries is the NIST GC Methods and Retention Index Library with RI data for 82,868 compounds, an increase of over 12,000 compounds from the 2011 version. Of these, 56,216 compounds are in the EI library. This brings the number of measured retention indices to 387,463.