Wiley Seminar: NIST Structure Search and MS Interpreter

The speaker, James Little, introduces the second part of a webinar series initially conducted for Wiley but now also shared on YouTube for broader access. He highlights the benefits of using his own software for the webinar, such as the ability to multitask between applications. James provides a brief overview of his experience as a retired research fellow from Eastman Chemical Company, where he specialized in unknown identification and reverse engineering of mixtures using mass spectrometry and other techniques. He now operates his own consultancy for mass spectrometry interpretation and has an extensive website with resources. The webinar will cover structure searches with NIST and MS Interpreter, with references and links provided for further information.

James demonstrates the process of conducting structure searches using the NIST software, starting with drawing a chemical structure and importing it into the program. He explains the importance of setting up library search options and saving configurations. The webinar covers how to import structures from drawing programs, perform searches for similar and exact structures, and utilize the compare window for viewing results. James also introduces MS Interpreter for correlating substructures and isotope ratios to ions in mass spectra, and he emphasizes the software's documentation and the availability of resources on his website for further learning.

The speaker discusses how to interpret search results, including understanding match factors and sorting parameters. He shows how to refine structure searches by adjusting settings such as delta mass to find more accurate matches. James also explains how to deal with duplicate structures and how to perform exact structure searches using the InChI key. He emphasizes the importance of exploring different libraries for structures, such as the Wiley, NIST, and Eastman libraries, and encourages attendees to participate in the fifth session about creating and sharing user libraries.

James introduces the MS Interpreter tool, which correlates chemical structures with mass spectra. He demonstrates how to add a structure to a spectrum and use the tool to calculate molecular weights and formulas. The webinar shows how to send a spectrum to MS Interpreter for analysis, where the software identifies the base peak and provides theoretical isotope ratios, helping users confirm the identity of compounds. James also discusses the importance of accurate mass data and how it can be used to determine molecular formulas with high precision.

The speaker uses MS Interpreter to analyze fragmentation patterns in mass spectra, showing how the software can identify and suggest possible structures for various ions. He explains how the software uses color coding to indicate the level of confidence in the suggested structures and how users can manually select substructures for further analysis. James also discusses the use of isotope patterns, particularly chlorine's distinctive pattern, to confirm compound identities.

James demonstrates how to customize the workspace in the NIST software for comparing different compounds, specifically focusing on isomers. He explains the process of selecting and comparing structures, clearing unnecessary windows, and using the compare window to analyze and contrast the mass spectra of various isomers. The webinar also touches on the ortho effect and how it influences fragmentation patterns, leading to different mass spectra for ortho isomers.

The speaker discusses the use of accurate mass data in MS Interpreter, showing how to import and analyze data with high precision. He explains how the software can calculate accurate masses for fragments and sort them by molecular formula and part per million error, allowing for the identification of compounds with high accuracy. James also provides tips on handling accurate mass data, such as reducing the number of significant digits for easier interpretation.

In conclusion, James thanks the Wiley team and other contributors for their support in creating the webinar series. He emphasizes the importance of using software and databases as aids in the identification process, not as the ultimate authority. James advises attendees to consider all available information, including NMR and sample history, before making identification claims. He encourages further learning in EI interpretation and mass spectrometry to improve analytical skills and ensure accurate and reliable results.