Use of inorganic, complex-forming ions for selectivity enhancement in capillary electrophoretic separation of organic compounds

Capillary electrophoresis (CE) is a powerful separation method based on the migration of charged species under the influence of electric field. The main merits of CE are high separation efficiency, short analysis time and small consumption of solvents and samples. However, the main drawbacks of CE are generally lower sensitivity compared to classical column-chromatographic methods.Selectivity and/or sensitivity of CE separation can be improved by forming complexes between analytes and a complex-forming reagent present as an additive in the background electrolyte (BGE). We focus this review primarily on the application of inorganic complex-forming reagents added to the BGE to separate organic ligands. We briefly mention common CE separations of inorganic analytes (mainly metal ions) using BGEs with organic ligands (e.g., hydroxycarboxylic or aminopolycarboxylic acids) as selectors.The review involves brief theoretical consideration of the significance of the effect of complex formation on separation selectivity and/or sensitivity in CE, but the major topic is critical evaluation of different inorganic complex-forming reagents used recently in the CE analysis of organic compounds, including:

(i)

borate, tungstate and molybdate in separating organic compounds possessing vicinal -OH groups;

(ii)

ligand-exchange CE and capillary electrochromatography in chiral analysis; and,

(iii)

the role of metal ions as central ions employed for selectivity enhancement of CE separation of various classes of organic compounds, including biopolymers.

     

Europium(III) Concentration Effect on the Spectroscopic and Photoluminescent Properties of BaMoO4:Eu

BaMoO₄:Eu (BEMO) powders were synthesized by the polymeric precursor method (PPM), heat treated at 800 °C for 2 h in a heating rate of 5 °C/min and characterized by powder X-ray diffraction patterns (XRD), Fourier Transform Infra-Red (FTIR) and Raman spectroscopy, besides room temperature Photoluminescence (PL) measurements. The emission spectra of BEMO samples under excitation of 394 nm present the characteristic Eu³⁺ transitions. The relative intensities of the Eu³⁺ emissions increase as the concentration of this ion increases from 0.01 to 0.075 mol, but the luminescence is drastically quenched for the Ba_0.855Eu_0.145MoO₄ sample. The one exponential decay curves of the Eu^{3+ 5}D₀→⁷F₂ transition, λ _exc = 394 nm and λ _em = 614 nm, provided the decay times of around 0.54 ms for all samples. It was observed a broadening of the Bragg reflections and Raman bands when the Eu⁺³ concentration increases as a consequence of a more disordered material. The presence of MoO₃ and Eu₂Mo₂O₇ as additional phases in the BEMO samples where observed when the Eu³⁺ concentration was 14.5 mol%.     

双锰卟啉应用于钼酸根电位传感器的研究

以[MnT(p-CH3)PP]2O为活性物质、以o-NPOE为增塑剂PVC膜制成的新型高效电位型传感器来测定MoO42-离子浓度。该电极具有线性能斯特斜率为30.5的响应特征,其工作浓度范围为2.1×10-6~1.0×10-1mol/L,pH范围为5.0~12.5,响应时间不超过15 s,对常见干扰离子有较高的选择性,并被应用于实际样品中MoO42-含量的测定。     

Ca1−xMo1−ySiyO4:Eux: A novel red phosphor for white light emitting diodes

Single phase of Ca_1−xMo_1−ySi_yO₄:Eu_x³⁺ (0.18?x?0.26, 0?y?0.04) was synthesized by solid-state method. The photoluminescence investigation indicated that Ca_1−xMoO₄:Eu_x³⁺ (0.18?x?0.26) could be effectively excited by 393 and 464 nm, and it exhibited an intense red emission at 615 nm. The introduction of Si⁴⁺ ions did not change the position of the peaks but strongly enhanced the emission intensity of Eu³⁺ under 393 and 464 nm excitations and showed very good color purity. The emission intensity of optimal Ca_0.8Mo_0.98Si_0.02O₄:Eu_0.2³⁺ sample (excited by 393 nm) was about 5.5 times higher than that of the phosphor Y₂O₂S:0.05Eu³⁺. So this phosphor could be nicely suitable for the application of the UV LED chips.     

聚乙烯醇存在下钼酸盐和罗丹明B光度法测定钪

在聚乙烯醇存在下，钪相杂多酸和罗丹明Ｂ（ＲＢ）形成离子缔合物，其最大吸收位于５７０ｎｍ，表观摩尔吸光系数ε值为５．６２×１０＾５Ｌ．ｍｏｌ＾－１．ｃｍ＾－１，服从比耳定律范围０－１．０μｇＳｃ／２５ｍＬ，检出限１．１ｎｇ／ｍＬ（ｎ＝９），考察了５０多种外来离子影响，缔合物的摩尔组成为Ｓｃ：Ｍｏ：ＲＢ＝１：１２：６，方法用于地质样品中钪的分析，结果满意。     

Tetraammonium Diglycinyl‐octamolybdate(VI) Dihydrate, (NH4)4[(NH3CH2CO)2(Mo8O28)] · 2 H2O

The reaction of ammonium heptamolybdate with hydrazine sulfate in an aqueous solution of glycine at room temperature yielded colorless crystals of (NH₄)₄[(NH₃CH₂CO)₂(Mo₈O₂₈)] · 2 H₂O. The crystal is monoclinic, space group C2/c (no. 15), a = 17.234 Å, b = 10.6892 Å, c = 18.598 Å, β = 108.280°, V = 3253.2 ų, Z = 4. The crystal structure contains ammonium cations and isolated octamolybdate(4–) anions, [(NH₃CH₂CO)₂(Mo₈O₂₈)]^4–, with two zwitterionic glycine molecules as ligands.     

PIXE Spectroscopy for Determination of Volatile Corrosion Inhibitor Concentration in Anticorrosion Polymer Films

Summary. Anti-corrosion polymer films used for 0 to 6 years were investigated to determine the type and content of volatile corrosion inhibitors (VCI) and how long the films emit it to protect the metal surface encased by the film. By FTIR and DSC low density polyethylene (LDPE) was identified as the polymer carrier. Particle induced X-ray emission (PIXE) spectroscopy of anti-corrosion polymer films revealed significant concentration of molybdenum implying that corrosion inhibitor was molybdate based. The films were divided into three groups according to different rate of the VCI concentration decrease with increasing age. The division of films into groups and diffusion of VCI was confirmed by significant decrease of Mo content determined by PIXE spectroscopy after accelerated ageing in vacuum at 50°C. It was concluded that films with initial concentration of Mo above 6000 ppm emit VCI for at least 6 years while the films with less than 4000 ppm of molybdenum do not emit the VCI in the ambient conditions.     

Solid and solution chemistry of protonated and deprotonated mononuclear molybdenum(VI) citrates

Mononuclear molybdenum(VI) citrates with variable degrees of protonation, (NH₄)₂[MoO₂(H₂cit)₂]·H₂O (1), (NH₄)₃[MoO₂(H₂cit)(Hcit)]·H₂O (2) and (NH₄)₅[MoO₂(Hcit)(cit)]·2.5H₂O (3) (H₄cit = citric acid), have been well characterized, where the citrate ligands in 1–3 coordinate bidentate with Mo, while the free carboxylates form very strong hydrogen bonds with α-alkoxy and β-carboxylic acid groups. The chelation of α-alkoxy and α-carboxy groups in citrate are compared with that of FeMo-cofactor in NifV^– Klebsiella pneumoniae nitrogenase. Solution ¹³C NMR spectra show that 1–3 dissociated partly in D₂O. The equilibria are calculated based on ¹H NMR spectra in solution.     

Effects of doping Fe cations on crystal structure and thermal expansion property of Yb2Mo3O12

Crystal structures and thermal expansion properties of Yb_(2-x)Fe_xMo_3O_(12)(x=0.0,0.6,1.0,1.1,1.4) solid solutions have been studied by X-ray powder diffraction(XRPD) at different temperatures.Rietveld analysis of the XRPD data shows that Yb_(2-x)Fe_xMo_3O_(12) solid solutions adopt orthorhombic structure and have variable thermal expansion coefficients controlled by the ratio of Yb~(3+) to Fe~(3+).Yb_2Mo_3O_(12) shows anisotropic negative thermal expansion property,induced by the reductions in average Yb-O-Mo angle and average apparent Mo2-O bond length with increasing temperatures.As more Yb~(3+) substituted by Fe~(3+),the linear thermal expansion coefficients of Yb_(2-x)Fe_xMo_3O_(12) increase from negative to positive.A near-zero thermal expansion coefficient of 0.55×10~(-6)K~(-1) for Yb_(0.6)Fe_(1.4)Mo_3O_(12) is observed in the temperature range of 573-873 K     

Sonochemical synthesized BaMoO4/ZnO nanocomposites as electrode materials: A comparative study on GO and GQD employed in hydrogen storage

Due to poor rate proficiency and electrochemical capacity of transition metal oxides, production electrode materials as operative way to develop the electrochemical performance is a crucial strategy to make sure the great electroactive sites and fast electron/ion diffusion route. In order to solve this problem, carbon-based nanocomposites as conductive substrates are applied. The nanostructured BaMoO₄/ZnO was produced by sonochemical method in the presence of tween 20 as stabilizing agent. Effect of graphene quantum dots (GQDs) and graphene oxide (GO) for developing hydrogen capacity of BaMoO₄/ZnO was studied by providing representative composites of BaMoO₄/ZnO-GQDs and BaMoO₄/ZnO-GO. For this purpose, GQDs was synthesized using green source of Spiraea crenata and the GO provided by commercial company. The structural analysis shows preparation of scales-like morphology of BaMoO₄/ZnO without any impurities through SEM, TEM, XRD, EDS and FT-IR characterization data. Also, the specific surface area for BaMoO₄/ZnO-GQDs (11 m²/g) and BaMoO₄/ZnO-GO (124 m²/g) nanocomposites increased by comparing to BaMoO₄/ZnO (9.1 m²/g). The resultant nanocomposites used as new active compounds for applying in hydrogen storage strategies using cyclic voltammetry and chronopotentiometry tests. Comprehensively, the hydrogen capacitance after 15 cycles was demonstrated on the nanostructured BaMoO₄/ZnO about 129 mAhg⁻¹. It demanded the maximum capacitance for BaMoO₄/ZnO-GQDs and BaMoO₄/ZnO-GO nanocomposites were 284 and 213 mAhg⁻¹ respectively, which was higher than the initial nanostructured BaMoO₄/ZnO. It was exposed from the carbon based structured that; the endorsed electrochemical hydrogen storage (EHS) performance is ascribed to the reaction of the redox pair of Mo⁶⁺ /Mo⁵⁺ at the active sites throughout the EHS procedure. This study delivers a novel plan and potential sorption electrode materials to progress the intrinsic action of conductive compounds.