Ionic liquids as mobile phase additives in high-performance liquid chromatography with electrochemical detection: Application to the determination of heterocyclic aromatic amines in meat-based infant foods

The beneficial effects of several ionic liquids (ILs) as mobile phase additives in high-performance liquid chromatography with electrochemical detection for the determination of six heterocyclic aromatic amines (HAs) have been evaluated for first-time. The studied ionic liquids were 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF₄), 1-hexyl-3-methylimidazolium tetrafluoroborate (HMIm-BF₄) and 1-methyl-3-octylimidazolium tetrafluoroborate (MOIm-BF₄). Several chromatographic parameters have been evaluated in the presence or absence of ILs, or using ammonium acetate as the most common mobile phase additive, with three different C18 stationary phases. The effect of the acetonitrile content was also addressed. In general, best resolution, lower peak-widths (up to 72.1% lower) and lower retention factors are obtained when using ILs rather than ammonium acetate as mobile phase additives. The main improvement was obtained in the baseline noise, being 360% less noisy for BMIm-BF₄, 310% for HMIm-BF₄, and 227% for MOIm-BF₄, when compared to ammonium acetate at +1000 mV. Different chromatographic methods using the best conditions for each IL were also evaluated and compared. Finally, the best chromatographic conditions using 1 mM of BMIm-BF₄ as mobile phase additive, the Nova-Pak^® C18 column, 19% (v/v) of acetonitrile content in the mobile phase, and +1000 mV in the ECD, have been applied for the chromatographic analysis of six HAs contained in meat-based infant foods. The whole extraction method of meat-based infant foods using focused microwave-assisted extraction and solid-phase extraction has also been optimized. Extraction efficiencies up to 89% and detection limits ranged between 9.30 and 0.165 ng g⁻¹ have been obtained under optimized conditions.     

Electrochemical study and MO — modeling of the reduction behaviour of some arylidene substituted derivatives of dibenz [b,e]-thiepin-5,5-dioxide-11-one

The electrochemical reduction of four arylidene substituted derivatives of dibenz-[b,e]-thiepin-5,5-dioxide-11- one has been studied by cyclic voltammetry on platinum (Pt) electrode in aprotic media (DMSO), coupled with spectral EPR techniques. From the analysis of cyclic voltammetry experiments, aided by digital simulations using DigiSim software, the kinetic and thermodynamic parameters were evaluated for each system. The electrochemical behaviour is strongly directed by the nature of the arylidene substituents bound to the central heterocycle. The electrochemical investigation and solvent dependent semiempirical modeling using the PM3 hamiltonian in the frame of AMPAC program package allowed a rationalisation of experimental data regarding the electrochemical reduction and the reactivity of the intermediate species involved.      

DTPA双酰胺杂环钆(Ⅲ)配合物的合成、表征与弛豫效能

通过二乙三胺五乙酸(DTPA)酸酐与一种新型杂环化合物的酰化反应,得到了双酰胺共价键链接、杂环化合物修饰的DTPA配体。再与GdCl₃·6H₂O反应得到相应的顺磁性钆(Ⅲ)配合物。通过元素分析、FTIR、1H NMR等手段表征了配体和金属配合物的结构,进而测定了配合物的纵向弛豫率(R₁)。结果表明,配合物分子稳定性很好,且在同等含钆量条件下,这种新型钆(Ⅲ)金属配合物的R₁(5.12 mmol·L-1·s-1)高于临床应用的磁共振成像对比剂Gd-DTPA(3.64 mmol·L-1·s-1)。     

葡萄糖与杂环化合物在甲酰胺中的焓相互作用参数

由于糖具有特殊的生物和生理性质 ,在工业生产中已有广泛应用 ,故其溶液热力学性质已成为人们感兴趣的研究课题之一 .糖在水溶液中的热力学性质已见文献报道 [1] ,但在非水体系中的有关数据则较少报道 .研究表明 ,溶剂介质的变化对溶质的溶剂化状态和溶质间相互作用的影响较大 ,选用酰胺为溶剂可以获得模拟蛋白质环境条件下的溶质 -溶剂、溶质 -溶质间相互作用的信息 [2～ 4] .本文利用微量量热法测得了葡萄糖在杂环化合物与甲酰胺的混合溶剂中的溶解焓 .如果把杂环化合物作为 x,葡萄糖作为 y,按照 Mc Millan- Mayer[5 ] 理论 ,1 mol葡萄…     

芳香杂环聚合物紫外-可见光谱性质的理论研究

在AM₁方法优化构型的基础上,用ZINDO/CI方法计算了系列芳香杂环聚合物的紫外-可见光谱,探索分子结构与其光学性质之间的关系.理论计算结果表明,模型化合物ABPBO,PBO,PBOV和PBODV的紫外-可见光谱最大吸收波长(λ_max)依次增加,且相应吸收强度与分子链共轭长度相关.根据线性递变规律推导的理论λ_max值与其实验值(薄膜干态紫外吸收)符合得较好.由于质子化效应等环境因素,溶液中测量值较理论值和薄膜紫外吸收偏大.     

Solid-Liquid Phase Transfer Catalytic Method for the Preparation of Acyclic and Cylic and Cyclic Ketene Acetals

Solid-liquid phase transfer catalytic elimination reaction for the preparation of acyclic and cyclic ketene acetals has been developed.     

A Facile One-Pot Synthesis of Highly-Functionalized Stable Heterocyclic Phosphorus Ylides in Aqueous Media

Phthalimide or succinimide undergo a reaction with dialkyl acetylenedicarboxylates and triphenylphosphine to produce highly-functionalized stable heterocyclic phosphorus ylides in good yields in water-tetrahydrofuran (6:1). This methodology is of interest because of the use of water as solvent, thus minimizing the cost, operational hazards, and environmental pollution.     

Polyamides from Aromatic BisaminesChloral Derivatives and Terephthaloyl Chloride by Interfacial Polycondensation

Investigations on a new class of polyamides obtained by interfacial polycondensation from amine-chloral derivatives, e.g., 2,2-bis(p-aminophenyl)-1,1,1-trichloromethane or 2,2-bis(p-aminophenyl)-1, 1-dichloroethylene and terephthaloyl chloride, have been carried out. It was found that the interfacial process proceeds in the most advantageous way in acidic medium at 0°C using equivalent volume amounts and equimolar concentrations of methylene chloride and water phases in the presence of a stoichiometric quantity of triethylamine as the hydrogen acceptor.     

某些含三唑取代的苯甲酸苯甲酰甲酯衍生物的合成

以三乙胺为缚酸剂，通过苯甲酸同ω－（１Ｈ－１，２，４－三唑－１－基）－ω－溴化苯乙酮反应，合成了六种含三唑取代的苯甲酸甲酰甲酯类化合物，具有较高收率。     

Oxidative kinetic resolution of heterocyclic sulfoxides with a porphyrin-inspired manganese complex by hydrogen peroxide

We have successfully reported here the low loading porphyrin-inspired high-valent manganese (IV)-oxo complex was applied in oxidative kinetic resolution (OKR) of racemic heterocyclic sulfoxides using the environmentally benign hydrogen peroxide for the first time. This approach allows for rapid OKR (0.5?h) of a variety of racemic sulfoxides (including pyridine, pyrimidine, pyrazine, thiazole, benzothiazole, thiophene) in excellent enantioselectivity (up to?>?99%?ee), simultaneously generating the corresponding sulfones in high yield (up to 80%). The catalytic system also showed an unexceptionable chemoselectivity for the sulfoxide substrates with hydroxyl groups in which only the sulfoxide group was oxidized. The practical utility of the method has been demonstrated in the OKR of gram-scale sulfoxides.