Probe Electrospray Ionization mass spectrometry in situ of soybean and nuts. Sequential ionization of carbohydrates and lipids.

G. PETROSELLI; M. K. MANDAL; L. C. CHEN; K. HIRAOKA; H. NONAMI; ERRA-BALSELLS, ROSA; ERRA BALSELLS, ROSA

Kyoto

Conferencia; 19th International Mass Spectrometry Conference, IMSC2012 Kyoto,; 2012

International Mass Spectrometry Foundation

Probe Electrospray Ionization mass spectrometry in situ of soybean and nuts. Sequential ionization of carbohydrates and lipids Gabriela Petroselli1, Mridul K. Mandal2, Lee C. Chen2, Kenzo Hiraoka2, Hiroshi Nonami3 and Rosa Erra-Balsells1 1 CIHIDECAR-CONICET, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, 3er P., Ciudad Universitaria, (1428) Buenos Aires, Argentina. 2 Clean Energy Research Center, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi, (400-8511) Japan. 3 Plant Biophysics/Biochemistry Research Laboratory, Faculty of Agriculture, Ehime University, Matsuyama, (790-8566) Japan. The probe electrospray ionization (PESI) is an ESI-based ionization technique that generates electrospray from the tip of a solid metal needle.1 In the present work, we describe the PESI mass spectra obtained in situ of soybeans and several nuts (peanuts, walnuts, cashew nuts, macadamia nuts, pistachios and almonds) using different solid needles as sampling probes. For comparative study ESI MS and PESI MS analyses were performed with methanolic extracts obtained from the seeds. Because seeds are rich in phospholipids, strongest signals detected in the positive ion mode were phosphatidylcholine, phosphatidylethanolamine and triacylglycerols of different fatty acid residues. Lipids were observed mostly as adducts with Na+ or K+. No significant differences were observed between both experiments, but the great advantage of using PESI MS is that no sample preparation is needed and minimum volume of organic solvents are required. In order to find the optimal experimental conditions for seeds analysis by PESI MS some variables were modified. (i) The effect of using different materials as probes and different needle diameters was evaluated. (ii) A typical protocol for lipids extraction from seed tissues was used and the extract MS analyses were compared with in situ analysis of the seeds. (iii) For direct analysis different solvents were used to keep wet the surface of the tissue. (iv) Two methods were used to acquire the mass spectra: the single-shot mode and the continuous mode. In the former, the droplet was left to be electrosprayed until the electrospray current decreased to zero and in the latter the droplet was periodically renewed. The results obtained showed that PESI MS is a valuable approach for in situ lipid analysis of seeds. Additionally, PESI mass spectrum is not probe material dependant. However, by modifying the titanium wire surface with pentafluorophenyl-triethoxysilane to make it more hydrophobic, time-dependent mass spectra could be obtained when single PESI mode is adopted allowing sequential analyses of carbohydrates and lipids. [1]  K. Hiraoka, K. Nishidate, K. Mori, D. Asakawa, S. Suzuki, Rapid Commun. Mass Spectrom. 21, 3139 (2007).