http://www.seipub.org/pcc/RSS.aspxen-US2016-10<p class="abstract">Redox Behavior of Riboflavin and Its Determination in Real Samples at Graphene Modified Glassy Carbon Electrode</p><ul><li>Pages 65-76</li><li>Author Atmanand M. BagojiSharanappa Nandibewoo</li><li>Abstract Improved electrochemical oxidative determination of riboflavin (RF) at a thin graphene film modified glassy carbon electrode (GF-GCE) has been established using cyclic and differential pulse voltammetric techniques. The graphene was characterized by SEM, TEM and electron diffraction studies. The surface area calculated for modified electrode was higher than the glassy carbon electrode which is responsible for more catalytic activity in the present system. Cyclic voltammetry was employed to unveil the electrocatalytic performance of graphene and two redox peaks were observed for RF with good intensity. The redox voltammetric behavior of RF at the sensor was quasi-reversible involving two electrons-two protons. At the surface of modified electrode, the redox reaction was adsorption-controlled. A probable electro-redox mechanism was proposed. Under the optimum conditions, a calibration curve of longer linearity for peak current and RF concentration in the range from 1.0 nM to 1.5 × 10-8 M was obtained with a detection limit of 1.0 × 10-10 M. The present method was applied to riboflavin determination in pharmaceutical and real samples with good recovery. There was no interference from any excipients, which indicates the specificity of the composite electrode. Furthermore, the fabricated RF chemical sensor exhibited excellent stability, remarkable catalytic activity and reproducibility towards RF determination. The method finds applications in clinical laboratory.</li></ul>http://www.seipub.org/pcc/PaperInfo.aspx?ID=30449Physical Chemistry Communicationshttp://www.seipub.org/pcc/PaperInfo.aspx?ID=304492016-10<p class="abstract">Bonding Character of Amino and Cyclopropyl Substituted Six-Membered Ring Carbenes: DFT/NMR and AIM Analysis</p><ul><li>Pages 77-86</li><li>Author Seyed Majid MusaviJavad Aman</li><li>Abstract A systematic B3LYP/6-311++G**//B3LYP/6-31+G* calculations of GIAO/CSGT-NMR (σd, σp, σii and ∆χanis) and AIM ( , and ε) are performed on some X-substituted six-membered ring carbenes (3a/3b, 4a/4b/4c, and 5a/5b; X=amino and cyclopropyl). The findings confirm the interaction of divalent centers with neighboring attached groups, either amino or cyclopropyl, but have a much more pronounced impact for the former. The N–Ccarbene bonds of all singlet carbenes are stronger than their corresponding triplets and the π-components also bring about higher charge transfer contributions as compared with the corresponding triplets. The large chemical shielding anisotropy at the Ccarbene could mainly be related to a low-lying n→π* transition, σxx,p. The extent of paramagnetic contribution is generally proportional to the inverse of singlet-triplet gaps ΔEs-t. Calculated 13Ccarbene chemical shifts for singlet states are significantly more downfield as compared with their corresponding triplets. Calculated σiis at the Ccarbene show that the amino and cyclopropyl groups have the same behavior in the polarization of the X–Ccarbene bond toward X, but the amino group has a more π back-donation ability. In the singlet carbenes, the absolute values of paramagnetic components decrease in the order of σxx,p > σyy,p > σzz,p, but in the triplet carbenes the order is almost reverse. The calculated ∆χanis values show that the electron delocalization to carbene center of all triplet carbenes is less than the corresponding singlet states.</li></ul>http://www.seipub.org/pcc/PaperInfo.aspx?ID=30546Physical Chemistry Communicationshttp://www.seipub.org/pcc/PaperInfo.aspx?ID=305462016-10<p class="abstract">Mechanism of Oxidation of Theophylline by Silver (III) Periodate Complex in Aqueous Alkaline Medium</p><ul><li>Pages 87-94</li><li>Author Arunkumar T. BuddanavarSharanappa Nandibewoo</li><li>Abstract The kinetics of oxidation of theophylline (TP) by diperiodatoargentate (III) (DPA) in aqueous alkaline medium at a constant ionic strength of 0.31 mol dm−3 was studied spectrophotometrically. The reaction between TP and DPA in alkaline medium exhibits 1:2 stoichiometry. The reaction is of the first order with respect to [DPA] and has a zero order in [TP] and unit order in [alkali]. The main oxidation product was identified as 3-methyl-2,6-dioxo-2,3dihydro-6H-purine-1(7H)-carbaldehyde by spot test, FT-IR and LC-MS spectral studies. A probable mechanism was proposed; the activation parameters were computed and discussed.</li></ul>http://www.seipub.org/pcc/PaperInfo.aspx?ID=31875Physical Chemistry Communicationshttp://www.seipub.org/pcc/PaperInfo.aspx?ID=318752016-10<p class="abstract">Thermochemical Study of Hardening Cement Mixtures Which Contained Simulated Radioactive Waste</p><ul><li>Pages 95-108</li><li>Author P.V. KozlovO.M. SlyunchevK.V. Kir'yanovI. V. MyalkinA.V. Knyaze</li><li>Abstract Heat generation of cement mixtures of various compositions was measured with the calorimetric method during hardening of solutions, which simulated liquid medium-level wastes (MLW) from the radiochemical plant and distillation residues obtained from evaporation of Nuclear Power Plant (NPP) liquid radioactive wastes. Thermal capacity was determined and heat generation was calculated for the processes of hydration and solidification of cement mixtures. Impact of dry mixture and solution compositions on heat generation was determined, as well as that of the solution-cement ratio. A scaled-up experiment was carried out to solidify a 4 m3 block of compound using the developed cement mixture with reduced heat generation. It was found that at hardening, the temperature in the specimen didn’t exceed 57ºС. This fact confirmed the efficiency of the measures undertaken to decrease heating up of the compound in the course of hardening. Applicability of the cementation technology was considered in relation to NPP distillation residues with subsequent storage of the obtained compound in pour- type compartments. It was demonstrated that the developed dry mixture compositions ensured compliance of the cement compound with the respective process and regulation requirements during NPP distillation residues hardening. Results of the study will help verify and, if necessary, adjust the mathematical model used in preliminary calculations to describe the process of storage compartment heating. It will allow developing a safe mode of filling compartments of the storage facility with the cement compound containing solidified MLW.</li></ul>http://www.seipub.org/pcc/PaperInfo.aspx?ID=31938Physical Chemistry Communicationshttp://www.seipub.org/pcc/PaperInfo.aspx?ID=319382016-10<p class="abstract">Reducing the Uncertainty in Terahertz Time-domain Reflection Spectroscopy</p><ul><li>Pages 109-112</li><li>Author Yijun XiePing SunHaiyan WangXiaochun Su</li><li>Abstract A self-referenced algorithm to extract the optical parameters of polycrystalline glucose based on the terahertz time-domain reflection spectroscopy was used. The results showed that the intrinsic phase error existing in the traditional algorithm was eliminated and the combined uncertainties decreased. Therfore, the self-referenced algorithm can obtain more accurate optical parameters than traditional algorithm. In addition, through analyzing the combined uncertainties, we explained the systematic and random influences on the optical parameters.</li></ul>http://www.seipub.org/pcc/PaperInfo.aspx?ID=34972Physical Chemistry Communicationshttp://www.seipub.org/pcc/PaperInfo.aspx?ID=34972