Bromotrimethylsilane as a selective reagent for the synthesis of bromohydrins

Glycerol, a by-product of biodiesel production, can be efficiently converted into α-monobromohydrin or α,γ-dibromohydrin with trimethylsilyl bromide (TMSBr), in solvent-free and mild reaction conditions.

Native mass spectrometry of human carbonic anhydrase I and its inhibitor complexes

Native mass spectrometry is a potent technique to study and characterize biomacromolecules in their native state. Here, we have applied this method to explore the solution chemistry of human carbonic anhydrase I (hCA I) and its interactions with four different inhibitors, namely three sulfonamide inhibitors (AAZ, MZA, SLC-0111) and the dithiocarbamate derivative of morpholine (DTC). Through high-resolution ESI-Q-TOF measurements, the native state of hCA I and the binding of the above inhibitors were characterized in the molecular detail. Native mass spectrometry was also exploited to assess the direct competition in solution among the various inhibitors in relation to their affinity constants. Additional studies were conducted on the interaction of hCA I with the metallodrug auranofin, under various solution and instrumental conditions. Auranofin is a selective reagent for solvent-accessible free cysteine residues, and its reactivity was analyzed also in the presence of CA inhibitors. Overall, our investigation reveals that native mass spectrometry represents an excellent tool to characterize the solution behavior of carbonic anhydrase. Graphic abstract

A Highly Selective Reagent Scheme for Scheelite Flotation: Polyaspartic Acid and Pb–BHA Complexes

Previous studies have proved that the lead complexes of benzohydroxamic acid (Pb–BHA) are effective collectors of scheelite flotations; however, the separation of scheelite from calcite needs depressants with high selectivity. In this study, we reported a novel depressant for calcite minerals, and Pb–BHA served as the collector of scheelite. The flotation behavior of polyaspartic acid (PASP) in a scheelite and calcite flotation that uses Pb–BHA was determined via flotation experiments. Furthermore, the selective adsorption of PASP on the mineral surfaces and the effect of PASP on the adsorption of Pb–BHA on the mineral surfaces were investigated through zeta potential measurements, X-ray photoelectron spectroscopy (XPS), crystal chemistry calculations, and Fourier transform infrared spectroscopy (FTIR) measurements. Thus, PASP demonstrated high selectivity in both scheelite and calcite and contributed to the successful separation of scheelite from calcite. PASP exhibited a higher adsorption capacity and stronger chemisorption with the active sites of calcium atoms on the calcite surface. The crystal chemistry calculations indicated that the distance of the PASP functional groups matched with the calcium distance of a calcite mineral surface, which can be attributed to the selectivity of PASP. Furthermore, the adsorption of PASP impeded the adsorption of Pb–BHA on the calcite surfaces, whereas the opposite was the case for scheelite. The mutually reinforcing selectivity of PASP and Pb–BHA considerably contributes to the efficient flotation separation of scheelite from calcite.

Utilization of Sodium Hexametaphosphate for Separating Scheelite from Calcite and Fluorite Using an Anionic–Nonionic Collector

This study presents a highly selective reagent system that utilizes sodium hexametaphosphate (SHMP) to improve the separation of scheelite from calcite and fluorite using an anionic–nonionic collector. The recoveries of calcite and fluorite decreased to 20% as the SHMP dose exceeded 6 × 10−6 mol/L, whereas that of scheelite remained at 85%. The interaction mechanisms of minerals with SHMP were investigated through equilibrium speciation, Zeta potential, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy analyses. SHMP exists as hydrogen phosphate anion in the aqueous solution with a pH of 7–12. Moreover, it may be adsorbed intensively on the positively charged surfaces of calcite and fluorite via electrostatic force or chelation with calcium ion to impede further adsorption of the assembled collector. By comparison, the adsorption of SHMP is feeble on the scheelite surface because of its negative charge. The roughing grade of low-grade scheelite ore is substantially improved from 0.74% to 1.65% compared with that in the contrast test in the absence of SHMP.

Gas Phase Reactions of Iron, Copper and Rhodium Cations with Monoterpenes

Monoterpene hydrocarbons C10H16 are emitted by the vegetation to the atmosphere, where they participate in the atmospheric chemistry and aerosols formation. Thus there is a need to analyse their concentrations selectively with measurement time less than 1 s. This task could not be solved solely by gas chromatography and one of the possible solutions is selective reagent ions in chemical ionization mass spectrometry techniques. This study presents product ion distributions of the gas phase single collision reactions of Fe+, Cu+ and Rh+ metal cations with seven monoterpenes: α-pinene, sabinene, myrcene, 3-carene, ocimene, β-pinene and α-phellandrene. Some distinctive product ion patterns were noticed: C5H8 loss in reactions with Fe+, C10H16 adduct formation with Cu+, and series of H2 losses in with Rh+. Application of these results are discussed, particularly that a combination of few reagent ions should be utilized in order to analyse monoterpenes mixture selectively.

Gas Phase Reactions of Iron, Copper and Rhodium Cations with Monoterpenes

Monoterpene hydrocarbons C10H16 are emitted by the vegetation to the atmosphere, where they participate in the atmospheric chemistry and aerosols formation. Thus there is a need to analyse their concentrations selectively with measurement time less than 1 s. This task could not be solved solely by gas chromatography and one of the possible solutions is selective reagent ions in chemical ionization mass spectrometry techniques. This study presents product ion distributions of the gas phase single collision reactions of Fe+, Cu+ and Rh+ metal cations with seven monoterpenes: α-pinene, sabinene, myrcene, 3-carene, ocimene, β-pinene and α-phellandrene. Some distinctive product ion patterns were noticed: C5H8 loss in reactions with Fe+, C10H16 adduct formation with Cu+, and series of H2 losses in with Rh+. Application of these results are discussed, particularly that a combination of few reagent ions should be utilized in order to analyse monoterpenes mixture selectively.