This work was initially done in 2006 at Pittcon as a course. Enhancements in hardware and software has greatly enhanced its application in the identification of surfactants. The following YouTube video and associated handout summarizes the overall approach and enhancements in the last 18 years.
YouTube Video Overview and Enhancements
YouTube Video Link (7.5 min)
YouTube Video Powerpoint
PowerPoint Link Used in Video
Course Resources
Class Presentation
Experimental and Discussion (Technical Report)
Eastman Excel Spreadsheet
The monomeric surfactants could be identified by either our SciFinder or ChemSpider using “known unknowns” approach. However, the oligomeric ones containing polyethylene glycol (PEG) are often more challenging since it is difficult to determine their lipophilic end groups. We have employed two different approaches for these types of surfactants.
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We use a residual molecular (RMW) to calculate a residual molecular weight (RMW) index for PEG-containing surfactants. The RMW index is then used to find candidate structures from our Eastman Excel spreadsheet. The candidate structures are refined with other data such as MS/MS or in-source collision-induced dissociation data to arrive at an exact identification. This method is based on nominal molecular and accurate molecular weight data.
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More recently, I became aware of the work of Michael Thurman and Imma Ferrer using Kendrick mass defect. They later published their work in the Journal of Analytical Chemistry. Their approach used Kendrick mass calculations [1,2] and accurate mass data. I updated my Eastman Excel spreadsheets to include Kendrick mass defects.
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The following example shows how one would calculate using either the residual molecular weight (RMW) or Kendrick mass defect. The RMW indices can also be calculated automatically using the Microsoft Excel MOD function.
Other Resources
Creating MSMS Libraries at Eastman
Eastman 2004 ASMS Poster on Surfactant Identification
Polysorbate Characterization by LCMS (Thermo)
NIST MSMS Search Software Course
Vendors Connection Approach to NIST Search Application
NIST Novel Hybrid Search for Extending Library Identifications