The library is an encyclopedic database of "fingerprints" used to identify chemical compounds with a technique called mass spectrometry. The method uses the unique 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 new edition of the library, NIST 05, adds approximately 20,000 new spectra, bringing the total number of compounds found in the database to more than 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 more than 25,000 different compounds. And a separate collection of more than 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. They have become widely used "fingerprints" for compounds in complex biological samples in fields such as proteomics and metabolomics. This is the first evaluated, general purpose MS/MS data library available to the general public.
Produced in collaboration with the Environmental Protection Agency and the National Institutes of Health, the NIST 05 library is available with Version 2.0d of the NIST MS Search Program for Windows through authorized dealers. Details are available from the NIST Standard Reference Data Program at www.nist.gov/srd/nist1a.htm.