CuCrAl和CuCrZr低温液相合成甲醇催化剂的研究

 用络合共沉淀法制备了CuCrAl和CuCrZr复合氧化物液相合成甲醇催化剂，其比表面分别达到119和116m2／g．在5．0～5．5MPa和383K条件下，分别用间歇式和流动式反应釜考察了催化剂的活性和稳定性．结果表明：CuCrAl和CuCrZr的活性均明显高于CuCr；CuCrAl的活性略高于CuCrZr，但甲酸甲酯（MF）的选择性明显低于CuCrZr；两者在12h内未见活性明显下降．甲醇钠在反应过程中部分转化为甲酸钠和NaOH．CuCrAl和CuCrZr有较高的氢解活性可抑制甲醇钠与MF生成甲酸钠，从而有较低的甲酸钠浓度．但是，Al2O3和ZrO2的酸性有利于甲醇脱水，引起甲醇钠水解生成NaOH．溶剂对CuCr基催化剂的活性和选择性有明显影响．对反应机理进行了讨论．     

高效液相色谱指纹图谱应用于地黄的研究

利用高效液相色谱建立了地黄的色谱指纹图谱。采用反相C1 8柱 (5 μm ,1 5 0mm× 4.6mm) ,流动相甲醇∶水 (V V =5∶95 ) ,检测波长为 2 80nm ,流速 1 .0mL min进行实验。根据相对保留值和相对面积值对色谱指纹图谱进行分析对比研究 ,建立了控制地黄药材质量的新方法。该法为中药样品的鉴定提供了较全面的信息 ,并为HPLC在复杂组分的样品分析领域开拓了新的应用途径。     

Synthesis and amino acid extraction abilities of chiral calix[4]arene triamides containing amino alcohol units

Herein the synthesis and extraction abilities of new d-/l-phenylalaninol substituted p-tert-butylcalix[4]arene triamide derivatives (3 and 4) towards amino acids are reported. These compounds (3 and 4) have been easily synthesized via aminolysis of p-tert-butylcalix[4]arene trimethylester (2) with d-/l-phenylalaninol in methanol-toluen solvent system at one step. The extraction properties of the prepared chiral calix[4]arene triamide derivatives (3 and 4) towards some selected amino acid methylesters are studied by liquid–liquid extraction. Results show that these chiral calix[4]arene triamide derivatives (3 and 4) exhibited a good affinity towards all amino acid species without any remarkably discrimination.     

High performance liquid chromatographic studies on lanthanides, uranium and thorium on amide modified reversed phase supports

The retention behavior of uranium, thorium and lanthanides has been investigated with amide modified reversed phase C₁₈ supports using α-hydroxy isobutyric acid (α-HIBA) as the mobile phase. Four structurally different amide moieties namely, 4-hydroxy-N,N-dihexyl butyramide (4HHBA), 4-hydroxy-N,N-di-2-ethylhexylhexanamide (4HEHHA), bis(N,N,N′,N′-2-ethylhexyl)malonamide (B2EHM) and N-methyl-tris(dihexylcarbamoyl-3-methoxy)pivolamide (MTDCMPA) have been synthesized and studied. Among the various amide coated columns, the supports modified with 4HHBA, B2EHM and MTDCMPA exhibit an interesting retention for uranium and thorium, which is different from 4HEHHA modified support. The retention time for uranium and thorium increases with increasing amide concentration for 4HHBA, B2EHM and MTDCMPA supports, while the same decreases with increasing 4HEHHA content. However, the separation factor for uranium and thorium is greater on a 4HEHHA support, compared to an unmodified C₁₈ column, reflecting the amide's preferential complexation of uranium over thorium.Columns modified with 4HHBA, B2EHM and MTDCMPA exhibit relatively higher retentions for lanthanides. However, MTDCMPA modified support shows a different elution profile for lanthanides compared to 4HHBA, and B2EHM modified columns. Individual separations of heavier lanthanides, i.e., from gadolinium to lutetium also have been achieved using 4HHBA and B2EHM modified supports.The influence of modifier content, mobile phase concentration and its pH on the retention of metal ions has also been studied. Based on these investigations, an efficient high performance liquid chromatographic method (HPLC) has been developed for the rapid separation of uranium from thorium as well as for the individual separation of heavier lanthanides.     

Predicting the performance of molecularly imprinted polymers: Selective extraction of caffeine by molecularly imprinted solid phase extraction

A rational design approach was taken to the planning and synthesis of a molecularly imprinted polymer capable of extracting caffeine (the template molecule) from a standard solution of caffeine and further from a food sample containing caffeine. Data from NMR titration experiments in conjunction with a molecular modelling approach was used in predicting the relative ratios of template to functional monomer and furthermore determined both the choice of solvent (porogen) and the amount used for the study. In addition the molecular modelling program yielded information regarding the thermodynamic stability of the pre-polymerisation complex. Post-polymerisation analysis of the polymer itself by analysis of the pore size distribution by BET yielded significant information regarding the nature of the size and distribution of the pores within the polymer matrix. Here is proposed a stepwise procedure for the development and testing of a molecularly imprinted polymer using a well-studied compound—caffeine as a model system. It is shown that both the physical characteristics of a molecularly imprinted polymer (MIP) and the analysis of the pre-polymerisation complex can yield vital information, which can predict how well a given MIP will perform.     

Development and validation of a capillary electrophoresis method for the determination of phenothiazines in human urine in the low nanogram per milliliter concentration range using field-amplified sample injection

A capillary zone electrophoresis (CZE) method with ultraviolet-visible detection has been established and validated for the determination of five phenothiazines: thiazinamium methylsulfate, promazine hydrochloride, chlorpromazine hydrochloride, thioridazine hydrochloride, and promethazine hydrochloride in human urine. Optimum separation was obtained on a 64.5 cm x 75 microm bubble cell capillary using a buffer containing 150 mM tris(hydroxymethyl)aminomethane and 25% acetonitrile at pH 8.2, with temperature and voltage of 25 degrees C and 20 kV, respectively. Naphazoline hydrochloride was used as an internal standard. Field-amplified sample injection (FASI) has been applied to improve the sensitivity of the detection. Considering the influence of parameters affecting the on-line preconcentration (nature of preinjection plug, sample solvent composition, injection times, and injection voltage) and due to the significant interactions among them, in this paper we propose for the first time the application of a multivariate approach to carry out the study. The optimized conditions were as follows: preinjection plug of water for 7 s at 50 mbar, electrokinetic injection for 40 s at 6.2 kV, and 32 microm of H3PO4 in the sample solvent. Also, a solid-phase extraction (SPE) procedure is developed to obtain low detection limits and an adequate selectivity for urine samples. The combination of SPE and FASI-CZE-UV allows adequate linearities and recoveries, low detection limits (from 2 to 5 ng/mL), and satisfactory precisions (3.0-7.2% for an intermediate RSD %).     

Determination of water-soluble vitamins in pharmaceutical preparations by reversed-phase high-performance liquid chromatography with a mobile phase containing sodium dodecylsulphate andn-propanol

Summary A reversed-phase liquid chromatographic method with sodium dodecylsulphate-n-propanolwater as mobile phase has been used to separate and determine six water-soluble vitamins in twelve minutes. The analytical characteristics linear range, sensitivity, detection limits, and precision were evaluated. The lowest detection limits were those of nicotinic acid (not usually present in pharmaceutical products), 0.7 mgL⁻¹, nicotinamide, 1.3 mg L⁻¹, and pyridoxine, 1.4 mg L⁻¹. When the method was applied to the determination of the vitamins in pharmaceutical samples the values found agreed with those on the labels.     

Cadmium speciation in Arabidopsis thaliana as a strategy to study metal accumulation system in plants

The strategy to identify cadmium deactivation mechanism in Arabidopsis thaliana has been developed using selective and sensitive hyphenated techniques. Cadmium concentrations, in main parts of the plant, were determined by ICP-MS and total amount was found as 0.43-0.44 μg g⁻¹ in leaves and 3.3-3.4 μg g⁻¹ in roots. Speciation of the metal complexes in cells was investigated by SEC-ICP-MS in order to estimate the accumulation process. Phytochelatins, desglycyl-phytochelatins and phytochelatins homologues lacking the N-terminal γ-linked glutamic acid were extracted from plant and were identified by RPLC-ESI-MS. Two-dimensional chromatography allowed to link the metal complexes separated by SEC with isoforms of phytochelatins analyzed by high resolution RPLC and confirm their significant responsibility for metal accumulation. The potential of the cadmium complexes speciation indicates that obtained results could be reliable source of knowledge to confirm the information coming from the well-known genomic sequence of Arabidopsis and to estimate the role of γ-glutamyl transpeptidase in metabolism of glutathione.     

Chiral separation of N-(trans-4-isopropylcyclohexylcarbonyl)-D,L-phenylalanine isomers by high performance liquid chromatography

Summary A high-performance liquid chromatographic method was developed for the chiral separation of a new anti-diabetic agent, N-(trans-4-isopropylcyclohexylcarbonyl)-D-phenylalanine, and its L-enantiomer. The separation was performed on a Sumichiral OA-3300 column. Optimized mobile phase was 0.025 mol.L⁻¹ ammonium acetate in methanol solution. UV detection was at 210 nm. Baseline chiral separation was obtained within 12 minutes. The detection limits are 80 pg for the D-enantiomer and 120 pg for the L-enantiomer. RSD of the method was below 1% (n=5).     

Brnsted酸性离子液体催化醛(酮)与二元醇的缩合反应

研究了以Bro¨nsted酸性离子液体1-正丁基-3-甲基咪唑磷酸二氢盐(BMImH2PO4)为催化剂,在不使用其它有机溶剂且无需脱水的条件下,于室温下进行醛(酮)与二元醇的缩合反应,得到了由中至高的转化率和高选择性.产物1,3-二口恶戊烷可以和反应物自动分层,后处理操作简单.过量的醇与离子液体可以多次重复使用,且醛(酮)的转化率无明显降低.