LC/MS Unknown Identifications Using MSMS Libraries Part IV: Importing MSMS Spectra
Mass Spec Interpretation Services/James Little: Importing MSMS Spectra
MS/MS (Tandem) spectra can be used to identify unknowns employing library searches. This is accomplished in much the same approach as that employed for EI GC-MS with the NIST search software. The much improved NIST Search Version 2.4 is included with the 2020 library release.
I will attempt to introduce the user to the use of the NIST Version 2.4 search software employing NIST, Wiley, “crowd-sourced (MoNA)”, and user libraries for the identification of unknowns.
NIST has an ambitious program to extend their already comprehensive, high-quality MS/MS databases.
See the following link: NIST Pipeline for Extending MS/MS Libraries
This involves a very comprehensive process for selecting pertinent compounds for purchase and subsequent analyses. The problem with variability of the spectra is reduced by analyzing the samples on a variety of instruments at a variety of energy levels (20 steps). In addition, many different precursor ions and fragment ions are characterized (MSⁿ). This has already led to a very large high quality library of accurate mass MS/MS spectra in the 2020 release version (31K compounds/1.3 M spectra) and the effort is ongoing.
The Part IV will cover:
Detailed Handouts including tables of content are available in the LabRulezLCMS library.
- Introduction of Presenter, James Little
- Table of Contents
- Series Topics
- Help Files for NIST Search
- NIST Software in General is “Windows Compliant”
- Abbreviations Used in Text and Useful Keyboard Sequences
- Methods for ImportingSpectra Directlyin MSP Format to NIST
- Mass Spec Manufactures Current Use of NIST Search
- Example of Capability Utilized by Agilent
- Example of Imported Agilent Spectrum
- Example of Mult-Spectra Import of Agilent Spectra
- Importance of Proper Settings in NIST Spectrum Import Options
- Importing Spectra Manually Indirectlyin MSP and Other Formats
- Exporting Spectra Manually in MSP and Other Formats
- Example of Typical NIST Entry in *.MSP Format
- Live YouTube Demonstration
- References with Internet Links
Future parts will focus on:
- Part V: NIST Structure Searches
- Part VI: MS Interpreter Correlation of Substructure to MSMS Ions
- Part VII: Using and Creating Other MSMS Libraries
- Part VIII: Identification of Unknowns with “Spectraless” Libraries