TUTORIAL: ION ACTIVATION IN TANDEM MASS SPECTROMETRY USING ULTRA-HIGH RESOLUTION INSTRUMENTATION

Tandem mass spectrometry involves isolation of specific precursor ions and their subsequent excitation through collision-, photon-, or electron-mediated activation techniques in order to induce unimolecular dissociation leading to formation of fragment ions. These powerful ion activation techniques, typically used in between mass selection and mass analysis steps for structural elucidation, have not only found a wide variety of analytical applications in chemistry and biology, but they have also been used to study the fundamental properties of ions in the gas phase. In this tutorial paper, a brief overview is presented of the theories that have been used to describe the activation of ions and their subsequent unimolecular dissociation. Acronyms of the presented techniques include CID, PQD, HCD, SORI, SID, BIRD, IRMPD, UVPD, EPD, ECD, EDD, ETD, and EID. The fundamental principles of these techniques are discussed in the context of their implementation on ultra-high resolution tandem mass spectrometers. © 2020 John Wiley & Sons Ltd. Mass Spec Rev     

A novel solution for simulating air overpressure resulting from blasting using an efficient cascaded forward neural network

Air overpressure (AOp) is a hazardous effect induced by the blasting method in surface mines. Therefore, it needs to be predicted to reduce the potential risk of damage. The aim of this study is to offer an efficient method to predict AOp using a cascaded forward neural network (CFNN) trained by Levenberg–Marquardt (LM) algorithm, called the CFNN-LM model. Additionally, a generalized regression neural network (GRNN) and extreme learning machine (ELM) were employed to demonstrate the accuracy level of the proposed CFNN-LM model. To conduct the CFNN-LM, GRNN, and ELM models, an extensive database, related to four quarry sites in Malaysia, was used including 62 sets of dependent and independent parameters. Next, the performances of the aforementioned models were checked and discussed through statistical criteria and efficient graphical tools. Finally, the results showed the superiority of CFNN-LM (R² = 0.9263 and RMSE = 3.0444) over GRNN (R² = 0.7787 and RMSE = 5.1211) and ELM (R² = 0.6984 and RMSE = 6.2537) models in terms of prediction accuracy. Furthermore, three different regression analysis metrics were used to perform the sensitivity analysis, and according to the obtained results, the maximum charge per delay (\(\beta\) = 0.475, SE = 0.115, t-test = 4.125) was considered as the most influential feature in modeling the AOp.

     

Synthesis of TiCr<Subscript>2</Subscript> intermetallic compound from mechanically activated starting powders via calcio-thermic co-reduction

Effect of mechanical activation of TiO2 and Cr2O3 oxides as starting materials was investigated for direct synthesis of TiCr₂. Differential thermal analysis (DTA) indicated that increasing the ball milling time resulted in lower exothermic reaction temperatures between molten Ca–Cr2O3 and molten Ca–TiO2. A model-free Kissinger type method was applied to DTA data to evaluate the reaction kinetics. The results reveal that the activation energy of the exothermic reactions decreased with increasing the milling time. The structure, oxygen content, and average particle sizes of the obtained TiCr₂ product were affected by the ball milling time of the starting materials. Increasing the milling time from 10 to 40 h decreased the average particle size and oxygen content of the obtained TiCr₂ from 10 to 2 μm and from 1690 to 1290 ppm, respectively. The X-ray diffraction (XRD) results showed that TiCr₂ compounds with metastable bcc phase can be produced using nano-sized starting materials, while only a slight amount of bcc phase can be obtained in the TiCr₂ compounds, using micron-sized starting materials. The TiCr₂ obtained by this method had a hydrogen absorption capability of 0.63 wt % and the kinetics of the hydrogen absorption increased for the 40 h milled sample.     

Production of ultrapure hydrogen via utilizing fluidization concept from coupling of methanol and benzene synthesis in a hydrogen-permselective membrane reactor

In this work, a novel fluidized-bed thermally coupled membrane reactor has been proposed for simultaneous hydrogen, methanol and benzene production. Methanol synthesis is carried out in exothermic side which is a fluidized-bed reactor and supplies the necessary heat for the endothermic side. Dehydrogenation of cyclohexane is carried out in endothermic side with hydrogen-permselective Pd/Ag membrane wall. Selective permeation of hydrogen through the membrane in endothermic side is achieved by co-current flow of sweep gas through the permeation side. A steady-state fixed-bed heterogeneous model for dehydrogenation reactor and two-phase theory in bubbling regime of fluidization for methanol synthesis reactor is used to model and simulate the integrated proposed system. This reactor configuration solves some observed drawbacks of new thermally coupled membrane reactor such as internal mass transfer limitations, pressure drop, radial gradient of concentration and temperature in both sides. The proposed model has been used to compare the performance of a fluidized-bed thermally coupled membrane reactor (FTCMR) with thermally coupled membrane reactor (TCMR) and conventional methanol reactor (CR) at identical process conditions. This comparison demonstrates that fluidizing the catalytic bed in the exothermic side of reactor caused a favorable temperature profile along the FTCMR. Furthermore, the simulation results represent 5.6% enhancement in the yield of hydrogen recovery in comparison with TCMR.     

Comparison of asphaltene structure and morphology under different deasphaltene methods

Problems associated with asphaltene deposition during the production, transportation, and processing of crude oils are some of the important issues in oil industry. Thus, accurate identification of structure and surface morphology of asphaltene should be investigated. In this study, asphaltene are isolated from an Iranian heavy crude oil under three different experimental conditions by using heat (thermal deasphaltene), heat and toluene (thermal-toluene deasphaltene), and n-heptane (n-heptane deasphaltene) as precipitation agent. The effect of isolation method on the crystallite structure and surface morphology of asphaltene is characterized by X-ray diffraction and scanning electron microscope technique, respectively. It is found that extraction procedure has a strong influence on the physicochemical properties of the isolated asphaltene. The results showed that at thermal deasphaltene solid such as micellar the shape was the dominant morphology of asphaltene particles that cause the least height of the crystallites and number of aromatic sheets in a stacked cluster. This morphology changes to semisolid smooth surface and agglomerated asphaltene with cavities by altering the separation method to thermal-toluene deasphaltene and n-heptane deasphaltene. The maximum heights of the crystallites belong to n-heptane deasphaltene.     

Paraffin dehydrogenation and hydrogenation of nitrobenzene to aniline: Optimal design and operating condition

In this study, a radial flow configuration is optimized using NSGA-II algorithm for simultaneous heavy paraffin dehydrogenation and hydrogenation of nitrobenzene to aniline. Main products yield (Olefin and Aniline) and selectivity are maximized as two objective functions. The Shannon's Entropy, LINMAP and TOPSIS methods as three decision making approaches are used to select the final solution of Pareto front. The optimization results are shown that production rate of olefin and aniline enhanced about 36.55 and 4.33 ton/day, respectively, based TOPSIS and LINMAP methods compared with the non-optimized configuration. In addition, selectivity is increased 5.75% in optimized configuration.     

Reactive extraction and LSER model consideration of lactic acid with tripropylamine+organic solvent systems from aqueous solution at room temperature

The extraction of lactic acid was done by tripropylamine (TPA) dissolved in seven single solvents (isoamyl alcohol, heptan-1-ol, hexan-1-ol, octan-1-ol, nonan-1-ol, decan-1-ol, and dodecanol). All measurements were carried out at 298.15 K. The extent to which the organic phase may be loaded with lactic acid is expressed as loading ratio, Z, its value extraction efficiencies, E, and overall particular distribution coefficients, D, were calculated. Equilibrium complexation constants for (acid:amine) (1:1), (1:2) have been determined according to Bizek's approach. The maximum removal of lactic acid accomplished was about 81% with isoamyl alcohol having 1.935 mol dm^− 3 initial concentration of TPA. All of the obtained data have been correlated by linear solvation energy relationship (LSER) model. LSER model results were compared with the experimental results and well agreement between them was observed. Regression coefficient (R²) of LSER model is 0.972.