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2018-2019 Lecture 8

  • North Carolina Biotechnology Center 15 TW Alexander Drive Durham, NC, 27703 United States (map)

Plenary Lecture:

“Are Mass Spectrometers Truth Machines?”

Dr. Russell Grant, Laboratory Corporation of America, Burlington, North Carolina

Student Lecture:

"In-situ Derivatization of Harmful Carbonyl Compounds in E-Cigarette Liquids During Nano-Electrospray Ionization Mass Spectrometry”

Tavleen Kochar, Laboratory of Professor Gary Glish, University of North Carolina-Chapel Hill, Department of Chemistry

Chemicals used as flavorings, such as diacetyl, cinnamaldehyde, benzaldehyde, and vanillin, are FDA approved products for ingestion, but are now being added into the liquid of e-cigarettes and have recognized associations with respiratory disease when inhaled. A common method used for detection and quantification of harmful carbonyl compounds involves derivatization of the aldehyde or ketone in conjunction with chromatographic separation prior to mass analysis. A caveat with utilizing chromatographic methods is that it involves run times on the order of several minutes. Derivatization reactions have been integral for chemical analysis of molecules that do not readily ionize and thus are not detected by mass spectrometry (MS). Specific derivatization reactions can be utilized to add a permanent charge to the analyte, thus improving MS limits of detection. One example of analyte derivatization involves using Girard’s reagents. Girard’s Reagent T (GirT) and Girard’s Reagent P (GirP) undergo a Schiff-base mechanism with a carbonyl compound and provide the analyte with a permanent, positive charge that increases ionization efficiency and improves sensitivity. Typically, a derivatization reaction is run for hours at elevated temperatures to get sufficient conversion to products, thus utilizing conventional derivatization and chromatographic techniques limit high throughput analyses. However, recently it has been demonstrated that reactions can be completed on-line on a microsecond timescale in a microdroplet generated through nano-electrospray ionization (nESI). The initial droplet size for nESI is around 1 µm in diameter, which is an order of magnitude smaller than that for ESI. The small droplet size created with nESI increases the probability of reactants to interact in the droplet. As the solvent from the charged droplet continues to evaporate, the surface area to volume ratio increases due to a decrease in volume, which in turn increases the concentration of the reactants in the droplet and accelerates the rate of formation of the products prior to mass analysis. Herein, we demonstrate simultaneous derivatization and analysis of carbonyl compounds using nESI-MS. The derivatization kinetics of GirT and GirP reacting with the carbonyls were studied in the generated microdroplets. This method has been utilized for direct qualitative and quantitative analysis of these harmful carbonyl flavorings in various e-liquids.

Earlier Event: April 10
2018-2019 Lecture 7