Ionization of Volatile Organics and Nonvolatile Biomolecules Directly from a Titanium Slab for Mass Spectrometric Analysis

Atmospheric pressure chemical ionization (APCI)-mass spectrometry (MS) and electrospray ionization (ESI)-MS can cover the analysis of analytes from low to high polarities. Thus, an ion source that possesses these two ionization functions is useful. Atmospheric surface-assisted ionization (ASAI), which can be used to ionize polar and nonpolar analytes in vapor, liquid, and solid forms, was demonstrated in this study. The ionization of analytes through APCI or ESI was induced from the surface of a metal substrate such as a titanium slab. ASAI is a contactless approach operated at atmospheric pressure. No electric contacts nor any voltages were required to be applied on the metal substrate during ionization. When placing samples with high vapor pressure in condensed phase underneath a titanium slab close to the inlet of the mass spectrometer, analytes can be readily ionized and detected by the mass spectrometer. Furthermore, a sample droplet (~2 μL) containing high-polarity analytes, including polar organics and biomolecules, was ionized using the titanium slab. One titanium slab is sufficient to induce the ionization of analytes occurring in front of a mass spectrometer applied with a high voltage. Moreover, this ionization method can be used to detect high volatile or polar analytes through APCI-like or ESI-like processes, respectively.

A New Acyclic Diterpene Glycoside from Nicotiana attenuata with a Mild Deterrent Effect on Feeding Manduca sexta Larvae

To investigate the role of secondary metabolites in the feeding behavior of Manduca sexta larvae feeding on Nicotiana attenuata, an aqueous acetone extract of the aerial parts of the plant was subjected to feeding-performance bioassay-guided fractionation. We isolated three 20- hydroxygeranyllinalool glycosides from the leaves of N. attenuata, which acted as mild deterrents to the feeding herbivore M. sexta. One of the diterpenoid glycosides, attenoside (3), is a novel natural product. The structures of the compounds were determined using APCI mass spectrometry and 1- and 2D-NMR spectroscopy.