Profiling Triglycerides Directly from Food Products using DESI-MS

In combination with a Waters LCT Premier, DESI was used to profile triglycerides on the surfaces of food products.  Tostitos chips were ground and extracted with MTBE. The extract was spotted on Whatman paper and analyzed using a 70/30 methanol and 10 mM ammonium acetate as the spray solvent. Five lipid species were identified using exact mass measurements as ammonium adducts. A Tostitos chip was then analyzed directly using 3/1/ 0.003% methanol / chloroform / ammonium acetate spray solvent.  Remarkably, the triglyceride profiles from the extracted sample and the sample analyzed directly using DESI produced the same results. 

(a) Direct Analysis of Tostitos Chip:

Spray solvent: 3/1 MeOH/CHCl₃/0.003%NH₄OAc

(b) Analysis of MTBE extract of Tostitos chips:

Spray solvent: 70/30 MeOH/10 mM NH₄OAc