Liquid extraction surface analysis (LESA) of food surfaces employing chip‐based nano‐electrospray mass spectrometry

Abstract

An automated surface-sampling technique called liquid extraction surface analysis (LESA), coupled with infusion nano-electrospray high-resolution mass spectrometry and tandem mass spectrometry (MS/MS), is described and applied to the qualitative determination of surface chemical residues resulting from the artificial spraying of selected fresh fruits and vegetables with representative pesticides. Each of the targeted pesticides was readily detected with both high-resolution and full-scan collision-induced dissociation (CID) mass spectra. In the case of simazine and sevin, a mass resolution of 100,000 was insufficient to distinguish the isobaric protonated molecules for these compounds. When the surface of a spinach leaf was analyzed by LESA, trace levels of diazinon were readily detected on the spinach purchased directly from a supermarket before they were sprayed with the five-pesticide mixture. A 30 s rinse under hot running tap water appeared to quantitatively remove all remaining residues of this pesticide. Diazinon was readily detected by LESA analysis on the skin of the artificially sprayed spinach. Finally, incurred pyrimethanil at a level of 169 ppb in a batch slurry of homogenized apples was analyzed by LESA and this pesticide was readily detected by both high-resolution mass spectrometry and full-scan CID mass spectrometry, thus showing that pesticides may also be detected in whole fruit homogenized samples. This report shows that representative pesticides on fruit and vegetable surfaces present at levels 20-fold below generally allowed EPA tolerance levels are readily detected and confirmed by the title technologies making LESA-MS as interesting screening method for food safety purposes.

Spatially‐resolved protein surface microsampling from tissue sections using liquid extraction surface analysis

“…This junction is maintained for a few seconds and this step could be repeated to improve the efficiency of extraction. This method is most commonly used for small molecule extraction on tissue sections [4,5] or in different types of surfaces like food [6], TLC plates [7] or contact lenses [8]. In our previous studies based on direct on-tissue trypsin digestion followed by liquid-microjunction extraction and shotgun proteomics analysis, we showed for the first time the possibility to retrieve from a spot size of 650 m in diameter (corresponding to an estimated number of 1900 cells) 1500 proteins with a variability of 1.6 ± 0.8% per experiments on both frozen or formalin fixed and paraffin embedded tissue section [9,10].…”

Fully automated laser ablation liquid capture surface analysis using nanoelectrospray ionization mass spectrometry

“…[18] One commercially available direct liquid extraction-based surface sampling/ionization system for MS is liquid extraction surface analysis (LESA ® ) implemented on the Triversa NanoMate robotic nanoelectrospray ionization (nanoESI) system. [15,[18][19][20][21] With LESA ® , a robot-controlled pipette tip is positioned above the surface spot to be sampled and a specific volume of the extraction solvent is dispensed onto the sample forming a liquid junction between the pipette tip and surface. The material extracted into the liquid junction is aspirated back into the pipette tip then nanoelectrosprayed and mass analyzed.…”

Lipidomics for Elucidation of Metabolic Syndrome and Related Lipid Metabolic Disorder

“…We have evaluated the novel technique called LESA in combination with a NanoMate system (Advion BioSciences) [87]. By LESA, most of lipid molecules were effectively extracted and detected from specific localized position of tissues, even though space resolution is lower than 1 mm in diameter.…”