NIST Releases a Major Upgrade of Mass Spectra Library

After three years of development, the National Institute of Standards and Technology (NIST) have released a major upgrade of the widely used NIST/EPA/NIH Mass Spectral Library.

The library is an encyclopedic database of "fingerprints" used to identify chemical compounds with a technique called mass spectrometry.

The method uses the masses of molecules to identify unknown chemicals. Samples are first vaporized, then ionized by stripping away one or more electrons, leading to fragmentation.

These fragments are finally sorted by their mass-to-charge ratios using magnetic or electric fields, producing a "mass spectrum." Even a sample of a pure element generally produces a spectrum with several peaks representing a unique distribution of masses due to isotopes with varying numbers of neutrons.

The edition of the library, NIST 05, adds approximately 20,000 spectra, bringing the total number of compounds found in the database to 163,000.

Each spectrum has been analyzed and critically evaluated to ensure that the library has the best possible current data.

The upgraded library also includes two important new classes of chemical reference data. Gas-phase "retention index" data-used in gas chromatography to identify volatile organic compounds-have been added for 25,000 different compounds.

And a separate collection of 2,000 tandem mass spectrometry (MS/MS) spectra has been added. MS/MS spectra arise from a process where the ionization and fragmentation steps are separated.