离子色谱-电感耦合等离子体质谱联用法测定水中痕量BrO-3及Br-

建立了离子色谱-电感耦合等离子体质谱联用技术(IC-ICP-MS)用于饮用水中的痕量BrO-3及Br-的测量.使用DIONEX Carbopac PA-100(4 mm×250 mm i.d.)在流速1 mL/min及5 mmol/L NH4NO3(pH 5.7)淋洗液下进行BrO-3和Br-的分离.该方法以100 μL进样量对BrO-3的检出限为0.0027 μmol/L(0.22 μg/L);对Br-的检出限为0.0067 μmol/L (0.54 μg/L).对水样的分析结果表明,所测矿泉水中的BrO-3浓度大大超出了世界卫生组织最新<饮用水水质准则>中所规定的溴酸盐的指导值,而所测量的青岛崂山区生活用水则未检出BrO-3.     

火焰原子吸收光谱法测定高纯氯化铷中的钠、钾

采用火焰原子吸收光谱法测定高纯氯化铷中钠和钾的含量。加入氯化铯作为抑制剂,消除了钠、钾的电离干扰。钠、钾测定结果的相对标准偏差分别为17．4％、8．6％,回收率分别为92％～103％、94％～105％。     

火焰原子吸收光谱法间接测定青霉素V钾

基于青霉素V钾在酸性条件下的水解产物可与Pb2 + 形成沉淀 ,用火焰原子吸收光谱法测定沉淀中铅的含量 ,可间接测定药片中青霉素V钾的含量。在优化条件下 ,测定青霉素V钾的线性范围为 5 .15× 10 -5～ 4 .12× 10 -4mol/L ,线性回归方程为A =2 .4 2× 10 3 c - 0 .0 6 3 1,相关系数为 0 .999 1,检出限为 7.392× 10 -7mol/L ,测定结果的相对标准偏差为 0 .0 6 %～ 0 .6 9% ,回收率为 97.8%～ 10 2 .0 %。     

钾元素对生物质主要组分热解特性的影响

采用热重-红外联用仪对松木及生物质主要化学组分半纤维素、纤维素、木质素的热解特性及钾元素对其热解特性的影响进行了研究.结果表明,半纤维素、纤维素、木质素发生热解的主要温度分别为200~350 ℃、300~365 ℃和200~600 ℃;半纤维热解产物中CO、CO₂较多;纤维素热解产物中LG和醛酮类化合物最多;木质素热解主要形成固体产物,气体中CH₄相对含量较高.三种组分共热解过程中发生相互作用使热解温度提高、固体产物增加,气体中CO增加而CH₄减少.添加K₂CO₃后半纤维素和纤维素热解温度区间向低温方向移动,固体产率提高.K对纤维素作用最明显,CO、CO₂气体与固体产物产率明显增加,醛酮类和酸类物质的产率降低;木质素受K影响相对较小,热解固体产物略有增加,挥发分中H₂O和羰基物质增加;三组分共热解减弱了钾元素的催化作用.     

Electronic structure and chemical bonding in K<Subscript>2</Subscript>V<Subscript>3</Subscript>O<Subscript>8</Subscript>

The calculations of the electronic structure of layered polyvanadate K₂V₃O₈ were made employing the spin-polarized tight-binding LMTO method. Calculated magnetic moment for K₄V₆O₁₆ compound phase equals 1.97 μ_B. V-O interactions were established to be dominating in the chemical bonding generation in this polyvanadate according to the estimated crystal orbital overlap population. The covalent bonds V(2)-V(2) in V(2)₂O₇ groups and electron density localization on vanadium atoms in isolated pyramids V(1)O₅ were found.     

Solvation Phenomena of Potassium Thiocyanate in Methanol–Water Mixtures

This paper reports the results of a variety of experiments carried out for understanding the solvation behavior of potassium thiocyanate in methanol–water mixtures. Electrical conductivity, speed of sound, viscosity, and FT-Raman spectra of potassium thiocyanate solutions in 5 and 10% methanol–water (w/w) mixtures were measured as functions of concentration and temperature. The conductivity and structural relaxation time suggest the ion–solvent and solvent-separated ion–ion associations increase as the salt concentration increases in the mixtures. The Raman band shifts due to the C–O stretching mode of methanol for the solvent mixtures reveal the formation of methanol–water complexes. The significant changes in the Raman bands for the C–N, C–S and O–H stretching modes indicate the presence of SCN⁻−solvent interactions through the N-end, “free” SCN⁻ and the solvent-shared ion pairs as potassium thiocyanate is added to the methanol–water mixtures. The relative changes corresponding to H–O–H bending and C–O stretching frequencies indicate that K⁺ is preferentially solvated by water in these solvent mixtures. The appearance and increase of the intensity of a broad band at ≈940 cm⁻¹ upon salt addition was attributed to the SCN⁻–H₂O–K⁺ solvent-shared ion pairs. No Raman spectral evidence for K⁺(H₂O)_n species was observed. The preferential solvation of K⁺ and SCN⁻ in the methanol−water mixtures was verified by the application of the Kirkwood−Buff theory of solutions. This theory confirms that K⁺ is strongly preferentially solvated by water, whereas SCN⁻ is preferentially solvated by the methanol component.     

Ion-exchange selectivity of a network calixarene-containing polymer obtained by the template synthesis on Na<Superscript>+</Superscript>, K<Superscript>+</Superscript>, and Ba<Superscript>2+</Superscript> matrices

The ion-exchange equilibrium in network polymers obtained from cis-2,8,14,20-tetraphenyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene by template synthesis on cations Na⁺, K⁺, and Ba²⁺ as matrices was studied. The selectivity coefficients of ion exchanges Ba²⁺-H⁺, Na⁺-H⁺, K⁺-H⁺, Na⁺-K⁺, and Na⁺-NH₄ ⁺ were determined. The template synthesis enhanced the affinity of the polymers to matrix-forming cations by 6–8 kJ mol⁻¹. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1919–1922, August, 2005.     

Quantum chemical models of alkali metal hydroxide-water-dimethylsulfoxide superbasic media (MOH-H<Subscript>2</Subscript>O-DMSO,M = Li,Na, K)

Models of alkali metal hydroxide-water-dimethylsulfoxide superbasic media have been constructed using Hartree Fock and DFT (B3LYP) quantum chemical methods; the structure and energies of anion complexes are considered. The hydroxide anion in the models is stabilized as complexes of OH^?·H₂O and OH^?· 2H₂O types.     

Heterobimetallic s‐Block Hydrides by σ‐Bond Metathesis

Reactions between PhSiH₃ and alkali‐metal diamidoalkylmagnesiates ([M{N(SiMe₃)₂}₂MgBu], M=Li, Na, K) provide either selective alkyl metathesis or the formation of polyhydride aggregates contingent upon the identity of the Group 1 metal. In the case of [M{N(SiMe₃)₂}₂MgBu], this reactivity results in a structurally unprecedented dodecametallic decahydride cluster species.     

Skin‐worn Soft Microfluidic Potentiometric Detection System

A flexible skin‐mounted microfluidic potentiometric device for simultaneous electrochemical monitoring of sodium and potassium in sweat is presented. The wearable device allows efficient natural sweat pumping to the potentiometric detection chamber, containing solid‐contact ion‐selective Na⁺ and K⁺ electrodes, during exercise activity. The fabricated microchip electrolyte‐sensing device displays good analytical performance and addresses sweat mixing and carry‐over issues of early epidermal potentiometric sensors. Such soft skin‐worn microchip platform integrates potentiometric measurement, microfluidic technologies with flexible electronics for real‐time wireless data transmission to mobile devices. The new fully integrated microfluidic electrolyte‐detection device paves the way for practical fitness and health monitoring applications.