Electron transfer dissociation (ETD) and collision-induced dissociation (CID) were used to investigate underivatized, metal-cationized oligosaccharides formed via electrospray ionization (ESI). Reducing and non-reducing sugars were studied including the tetrasaccharides maltotetraose, 3α,4β,3α-galactotetraose, stachyose, nystose, and a heptasaccharide, maltoheptaose. Univalent alkali, divalent alkaline earth, divalent and trivalent transition metal ions, and a boron group trivalent metal ion were adducted to the non-permethylated oligosaccharides. ESI generated [M + Met], [M + 2Met], [M + Met], [M + Met - H], and [M + Met - 2H] most intensely along with low intensity nitrate adducts, depending on the metal and sugar ionized. The ability of these metal ions to produce oligosaccharide adduct ions by ESI had the general trend: Ca(II) > Mg(II) > Ni(II) > Co(II) > Zn(II) > Cu(II) > Na(I) > K(I) > Al(III) ≈ Fe(III) ≈ Cr(III). Although trivalent metals were utilized, no triply charged ions were formed. Metal cations allowed for high ESI signal intensity without permethylation. ETD and CID on [M + Met] produced various glycosidic and cross-ring cleavages, with ETD producing more cross-ring and internal ions, which are useful for structural analysis. Product ion intensities varied based on glycosidic-bond linkage and identity of monosaccharide sub-unit, and metal adducts. ETD and CID showed high fragmentation efficiency, often with complete precursor dissociation, depending on the identity of the adducted metal ion. Loss of water was occasionally observed, but elimination of small neutral molecules was not prevalent. For both ETD and CID, [M + Co] produced the most uniform structurally informative dissociation with all oligosaccharides studied. The ETD and CID spectra were complementary. Graphical Abstract ᅟ.

Thermodynamic assessment of electrochemical reduction of TiO2 to Ti metal in CaCl2 molten salt electrolyte is discussed. The conversion of TiO2 to Ti takes place via multi-step reduction process that involves formation of several intermediates or sub-oxides of titanium at different reaction conditions. A complete understanding of these redox chemical reactions, and change in reaction Gibbs energy is very essential for efficient extraction of the Ti metal. This research article discusses the thermodynamic modelling studies on the formation of different titanium sub-oxides and corresponding reaction conditions (change in Gibb’s energy, temperature, and pressure) during TiO2 reduction to Ti metal.

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