Glucose glass films: A matrix for mass spectrometry that mimics aqueous solution behavior

Abstract

This study demonstrates that an amorphous film of glucose has many of the features of water as a medium for solvating ions and, at low concentrations, maintaining ion pair separation. Aqueous solutions of glucose containing dissolved salts are evaporated to form a homogeneous glucose glass where the distribution of the solute in solution is preserved in the evaporated glass film. Cluster ions form in aqueous solutions at high solute concentration, and glucose films made from these solutions form gas-phase cluster ions when the film is excited by a high energy density pulse. These cluster ions do not form in dilute solutions and are not present in the mass spectrum of ions desorbd from films prepared from these solutions. Non-polar ions concentrate at the surface of aqueous solutions owing to the hydrophobic interaction and glucose glass films prepared from these solutions show, by mass spectrometry, that these features are retained in the glucose film. The salts studied include KCI, NaBr, LiCF,SO, , (tert-butyl),NI and (C,HS),NBF,. The concentration of the salt is the important variable in the study and ranges from a mole fraction of O.l-lO-,.For non-polar ions, the abundance of the molecular ion is not significantly changed over a wide range of dilutions.

Determination of the Anomeric Percentages of α- and β-D-(+)-Glucose in Glucose Glasses Used for Solid-Matrix Luminescence Spectrometry with Proton Nuclear Magnetic Resonance Spectrometry

“…However, in this case, the anom eric percentages obtained corresponded to the equilibrium percentages of aand b-D-(1)-glucose in D 2 O. 17 The NM R signals from the protons of the OH-1 groups on the anomeric carbon (C 1 ) of D-(1)-glucose were assigned by comparing the chemical shifts and J 1,O H-1 proton-proton coupling constants of the two anomers in M e 2 SO-d 6 to similar values reported in the literature. Coxon 16 12,14 As discussed earlier, when a-D-(1)-glucose crystals are melted, anomerization to b-D-(1)-glucose occurs.…”

PDMS-chemistry of angiotensin II and insulin in glucose glass thin films

“…The details of the preparation of the glucose films has been described elsewhere [6]. A brief summary of the salient features is given here.…”

“…At some point in the evaporation process, the analyte molecules are locked into position and when the thin film forms, the distribution of analyte molecules in the film retains some of the features of the bulk solution. In our first studies using this concept, we showed that hydrophilic ions are distributed throughout the film and that glucose molecules occupy surface sites [6]. Hydrophobic ions concentrate at the surface and deplete the concentration of glucose molecules at the surface, a phenomenon characteristic of the FAB method.…”

“…Influenced by the success of Barber's FAB method and the desire to put more chemistry-related variables into PDMS, a few years ago we introduced the concept of using glucose glass films as a matrix [6]. The idea was that an aqueous solution of an analyte would have a composition dependent on concentration and pH and a distribution between the bulk and surface modulated by the hydrophobic interaction.…”