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Identify Unknown Compounds from EI (GC/MS) and MS/MS Spectra with the World’s most widely used and trusted Mass Spectral Reference Library.

The NIST23 (2023) mass spectral library, the successor of the NIST20/17/14, is a fully evaluated collection of electron ionization (EI) and MS/MS mass spectra, with chemical and GC data, plus search software to identify your own unknown spectra. It is a product of a more than three decade, comprehensive evaluation and expansion of the world’s most widely used mass spectral reference library by a team of experienced mass spectrometrists at the National Institute of Standards and Technology (NIST) in which each spectrum was examined for correctness.

On this page we will provide you with a list of the NIST23’s new features and benefits, it’s components, and the key enhancements of the NIST23 compared to previous versions. In addition, we will provide a short description of the analysis tools of both the Electron Ionization (EI) MS Library and the Tandem (MS/MS) Library.

New Features and Benefits of the NIST23, includes:

  • Hundreds of thousands of EI-MS spectra, MS/MS spectra, GC data & retention indices, and/or chemical name/structures.
  • Major expansion in coverage of analytically important compounds of all classes, based on documented importance of each compound.
    • 394K Electron Ionization (EI) Spectra
      • 347,100 Compounds (40K increase)
      • 46,954 Replicate Spectra
    • 492K Retention Index (RI) Values
      • 153K RI Compounds with EI (>40K increase)
      • AI-RI Estimates for All EI Compounds
  • All compounds are evaluated with derivatives, retention indices and class information, and are selected for analytical relevance.
  • NIST has made significant enhancements to their metadata and their software, Mass Spectral Search 3.0.
  • Major Spectrum Type choice (EI, Tandem, Peptide, All) helps to suppress display of search parameters most probably not used.
  • Name search sorting has been increased from 19 to 249 characters; the list of names has been split into two panes: compound list in the upper pane and spectrum list in the lower pane. All spectra derived from a selected compound are shown in the spectrum list (EI: replicate, derivatives, stereoisomers; Tandem: energy, instrument, fragmentation type).
  • A list of ‘Other Databases’ (compound references) for each compound has been significantly extended.
  • Added a new search method: Partial Spectrum Search – for searching with abbreviated spectra.
  • All retention indices are displayed in the EI hit list. They are used for EI search with RI match factor correction. If experimental data is not available for a compound, a reliable AI-predicted value is used in its place.
  • Hovering a mouse pointer around a peak in a spectrum plot displays peak annotation.

NIST23 Components:

NIST23 is not just a mass spectral library. It contains these components:

  • Electron Ionization (EI) Mass Spectral Library – 394K carefully evaluated spectra of 347,000 unique compounds, with identifications, nearly all with chemical structures. 40K increase from NIST20 (largest EI increase ever).
  • Tandem (MS/MS) Library – 2.4 million spectra of 51K compounds (60% more than NIST20), 186K precursor ions.
    • Covers a variety of fragmentation methods: 49,590 HRAM (high res accurate mass) compounds, 50,071 QTOF/HCD/IT-HRAM/QqQ compounds, 49,561 ion trap (low res, up to MS4) compounds, and 561 APCOI HRAM compounds.
    • Variety of precursor ion types: 44,191 protonated, 19,620 deprotonated, 14,318 water/ammonia loss, and 44,547 other in-source generated.
  • Gas Chromatography (GC) data library – 492K retention index values (Kovats/Lee), 153K compounds in the EI library, covering both polar and non-polar columns. Includes retention indices with GC column conditions and literature citations.
  • NIST MS Search Software (version 3.0) – software for searching (identifying) compounds from their mass spectra and for browsing mass spectral libraries. Also includes MS interpretation programs for analyzing mass spectra on the basis of chemical structure, molecular formula, isotopic patterns, and more.
  • AMDIS Software – software for deconvoluting gas/liquid chromatograms.
  • Documentation – approximately 50-page electronic manual on setup and basic usage. Additional information is in the help files.

Key Enhancements:

Enhancements 2023 from 2020
  • EI Library adds 40K more compounds with retention indices, most selected, measured, and evaluated by NIST.
  • MS/MS Tandem Library grown to 51K compounds, all at multiple fragmentation energies and conditions. 66% more compounds. 80% more spectra. 2.4M Spectra.
  • NIST MS Search 3.0 (new release) made significant enhancements to its metadata and software.
  • Upgrade discount for any previous versions.
Enhancements 2020 from 2017
  • Increased coverage and quality in all libraries (EI-MS, MS/MS, and GC RI). Nearly 2x increase in MS/MS (1.3M), 40K more EI, 40K more GI-RI. New EI compounds added for importance and measured at NIST, thoroughly evaluated.
  • NIST MS updated: GC retention index estimated, new compound selection process, new library building method, new evaluation process, MS interpreter updates.
  • Upgrade discount for any previous versions.
Enhancements 2017 from 2014
  • Increased coverage and quality in all libraries (EI-MS, MS/MS and GC RI). Nearly 3x increase in MS/MS.
  • New and improved search algorithms (e.g., hybrid search).

NIST23 Electron Ionization (EI) Analysis Tools

The Electron Ionization (EI) library in the 2023 Release is a full featured MS Library search/display program. It allows for multiple search types and display modes with five tab views (spectrum search, feature search, compare, name/spectrum, and user library).

Hybrid Search for EI Analysis
The 2023 EI Release also includes the NIST Hybrid Search Tool that allows for identification of compounds not in the library.This function helps you find ‘modified’ library IDs and Masses of modifications with their shifted peaks. Hybrid Search uses MW estimate.

MS Interpreter for EI Analysis
The MS Interpreter connects peaks to plausible fragments or structures, confirms ID’s, computes fragment masses.

AMDIS for EI Analysis
AMDIS is a sophisticated software program used for GC-Ms data interpretation. In the NIST23 EI Release, AMDIS ‘purifies’ (EI) spectra and connects to NISTMS.

NIST23 Tandem (MS/MS) Analysis Tools

For each Compound in the 2023 Release of the NIST Tandem (MS/MS) Library, Compound names and synonyms are displayed as well as all related Spectra, Energies, Fragmentation Types, In-Source, Ions, and many more. The program also allows you to filter IDs by spectrum type.

Hybrid Search for MS/MS Analysis
The 2023 Tandem (MS/MS) Release also includes the NIST Hybrid Search Tool that helps you find compounds that are not in the library and confirm IDs. Hybrid Search uses peaks and losses and shows shifted peaks. The Hybrid Search function is therefore recommended for routine use. It also offers PFAS Illustrations, which are applicable to many classes.

MS Interpreter for MS/MS Analysis
The MS Interpreter of the Tandem (MS/MS) 2023 Release offers direct access from NISTMS. The program offers chemical formula calculators, an isotope calculator, any resolutions +/- charge and multiple display options. MS Interpreter can be used to find formula from delta mass, and to connect peaks to structure (fragments).

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