2-(9-蒽基)-2-甲氧基乙酸乙酯的高效液相色谱手性拆分

以键合在5 μm硅胶上的纤维素-三(二甲基苯基氨基甲酸酯)为色谱柱的手性固定相,采用高效液相色谱(HPLC)法对外消旋的2-(9-蒽基)-2-甲氧基乙酸乙酯进行了手性拆分.对影响2-(9-蒽基)-2-甲氧基乙酸乙酯拆分的三个重要因素:流动相组成、流速、色谱柱温度进行了研究.实验结果表明,在流动相组成为正已烷-异丙醇(94/6,V/V),流速1.0 mL/min,柱温20℃的条件下,2-(9-蒽基)-2-甲氧基乙酸乙酯对映体得到很好的分离,分离度为3.63.     

RP-HPLC测定反式-2-硝基乙烯基噻吩的含量

建立了反相高效液相色谱测定反式-2-硝基乙烯基噻吩含量的方法.采用shim-pack C18柱(5 μm,4.6 mm i.d.×250 mm),流动相为V(乙腈)∶V(pH 3的KH2PO4水溶液)=50∶50,流速为1.0 mL/min,检测波长为210 nm.外标法定量,反式-2-硝基乙烯基噻吩在0.002～0.1 mg/mL浓度范围内呈良好的线性关系,线性回归系数(r)为0.9998,平均回收率为99.80%,RSD=0.67% (n=9).     

2-(2-噻唑偶氮)-对-甲酚螯合物反相高效液相色谱同時分离测定镍、钴的研究——合金中微量钴和镍的测定

本文研究了2-(2-噻唑偶氮)-对-甲酚(TAC)与镍(Ⅱ)、钴(Ⅱ)螯合物的柱前衍生条件和液相色谱的分离条件。于KYWG-C_(18)柱上,用含有0.03mol/L KH_2PO_4-Na_2HPO_4(pH7.77)和2.5×10~(-4)mol/L TAC的甲醇-四氢呋喃-水(40∶10∶50 V/V)混合液为流动相,流速为1.0mL/min。于580nm处检测。该法用于四种标准合金中镍和钴的测定,回收率在98%～101.5%之间。Ni(Ⅱ)和Co(Ⅱ)的检出限(信噪比为2∶1)分别为0.2ng和1.5ng。建立了同时测定镍,钴的高灵敏、高选择性,快速的HPLC-光度法。     

高效液相色谱检测反应香精中的2-氨基-N-甲基-5-苯基咪唑并吡啶(PhIP)方法研究

建立了用高效液相色谱快速检测反应香精中2-氨基-N-甲基-5-苯基咪唑并吡啶的方法. 反应香精中的2-氨基-N-甲基-5-苯基咪唑并吡啶用二甲基甲酰胺直接超声振荡提取; 高效液相色谱的色谱柱为Eclipse XDB-C18 (250 mm×4.6 mm, 5 μm); 流动相为V(二甲基甲酰胺)∶V(甲醇)∶V(水)=8∶50∶42; 流速为0.5 mL/min; 光电二极管阵列检测器检测波长为UV-327 nm. 10种反应香精中均未检出该种物质, 回收率为78.9%～85.9%, 检出限为19.2 ng/mL.     

4-(6-甲基-2-苯并噻唑偶氮)间苯二酚作螯合剂反相HPLC分离测定V(V)、cu(Ⅱ)、co(Ⅱ)、Ni(Ⅱ)、cr(VI)

本文提出用4-(6-甲基-2-苯并噻唑偶氮)间苯二酚(MBTAR)为柱前衍生试剂,用含有15mmol/L TBA·Br,10mmool/L pH6.0 HAc-NaAc缓冲溶液的甲醇-水(75/25,V/V)混合溶液作流动相,在C_8柱上分离和测定了V(V)、Cu(Ⅱ)、Ni(Ⅱ)、co(Ⅱ)和Cr(Ⅵ)。当信噪比为3时,其检出限为0.15～6.1ppb。本法干扰少,分离时间短,应用于人发分析,结果令人满意。     

固相萃取-高效液相色谱法测定焦糖色素中副产物2-甲基咪唑、4-甲基咪唑和2-乙酰基-4-(1,2,3,4-四羟基丁基)咪唑

建立了固相萃取法结合高效液相色谱同时检测焦糖色素中2-甲基咪唑(2-Methylimidazole,2-MEI)、4-甲基咪唑(4-Methylimidazole,4-MEI)和2-乙酰基-4-(1,2,3,4-四羟基丁基)咪唑(2-Acetyl-4-(1,2,3,4-tetrahydroxybutyl) imidazole,THI)的方法.样品经加水涡旋提取后,经混合型强阳离子交换固相萃取小柱富集净化,以乙腈-0.05％氨水(10∶90,V/V)为流动相,流速为0.6 mL/min,用反向色谱柱Polaris C18-A(250 mm×4.6 mm,5μm)柱分离,分别在二极管阵列检测器215 nm波长条件下检测焦糖色素中的2-甲基咪唑、4-甲基咪唑和287 nm波长条件下检测2-乙酰基4.(1,2,3,4-四羟基丁基)咪唑的含量.2-甲基咪唑、4-甲基咪唑和2-乙酰基-4-(1,2,3,4-四羟基丁基)咪唑在0.2～ 20 mg/L之间线性关系良好(r＞0.9996),在10,25和100 mg/kg添加浓度的回收率范围为75.3％ ～93.4％,相对标准偏差均小于10％,检出限分别为为2.6,3.0和1.5 mg/kg,定量限分别为8.5,10.0和5.0 mg/kg.     

1─(2─吡啶偶氮)─2─萘酚─6─磺酸衍生化反相高效液相色谱法测定铁、钴、镍

本文研究了水溶性试剂1-(2-吡啶偶氮)-2-萘酚-6-磺酸(PAN-S)与铁(Ⅱ)、钴(Ⅱ)和镍(Ⅱ)之螯合物的衍生和液相色谱分离条件.在Nova-Pak^TMC₁₈柱上,用含10mmol/L的pH5.0的醋酸-醋酸钠缓冲溶液的甲醇-水溶液(50:50,V/V)作流动相,溴化四丁基铵(TBA·Br)作离子对试剂,流动相流速为1.0mL/min,在550nm波长处进行光度检测.在Ⅱmin内用高效液相色谱分离测定了Fe(Ⅱ)、Co(Ⅱ)和Ni(Ⅱ)与PAN     

新型药物辅料2-羟丙基-β-环糊精的色谱分离纯化

利用薄层色谱方法对碱浓度为1.5%、β-环糊精∶环氧丙烷(摩尔比)=1∶21的条件下生成的2-羟丙基-β-环糊精进行了定性分析,并通过对展开剂的选择和优化,得到了3种能有效分离不同取代度2-羟丙基-β-环糊精的展开剂体系,分别为正丙醇-水-浓氨水(6∶3∶1,V/V),异丙醇-水-浓氨水(6∶4∶0.5,V/V)和乙醇-水-浓氨水(6∶3∶0.8,V/V)。通过以乙醇体系为洗脱剂的硅胶柱色谱对其进行分离纯化,得到了两种不同取代的2-羟丙基-β-环糊精。经过ESI-MS谱图分析,确定分离后产品分别为单取代和双取代2-羟丙基-β-环糊精。     

反相高效液相色谱测定钴和镍的1-(5-溴-2-吡啶偶氮)-2-萘酚-6-磺酸螯合物

研究了1-(5-溴-2-吡啶偶氮)-2-萘酚-6-磺酸与钴(Ⅱ)和镍(Ⅱ)之螯合物的衍生和液相色谱分离条件。于Zorbax ODS柱上,用含0.01mol/L HAC-NaAc(pH 5.5)的乙腈-四氢呋喃-水(24:5:71,V/V)作流动相,流速0.7ml/min淋洗,于570nm检测。本方法已用于镍矿、催化剂回收液和人发样品的分析。     

高效液相色谱法测定纺织品中1-甲基-2-吡咯烷酮的含量

建立了纺织品中1-甲基-2-吡咯烷酮(N-Methylpyrrolidone,NMP)的高效液相色谱检测方法。样品经超声提取,采用ZORBAX SB-C18色谱柱分离,流动相为乙腈-水(30/70,V/V),检测波长210nm。结果表明,在0.4~48mg/L范围内,NMP的响应峰面积与其质量浓度呈良好的线性关系,相关系数r=0.9997,检测限(S/N=3)为0.2mg/kg,定量限(S/N=10)为0.4mg/kg,平均回收率为80.6%~108.6%。方法具有较高的灵敏度,可简便、快速地测定纺织品中NMP的含量。     

Separation and simultaneous determination of niobium and tantalum in steel by reversed-phase high-performance liquid chromatography using 2-(2-pyridylazo)-5-diethylamino phenol as a pre-column derivatizing reagent

A method for the simultaneous determination of Nb and Ta in steel and alloy by reversed-phase high-performance liquid chromatography (RP-HPLC) was proposed. 2-(5-Bromo-2-pyridylazo)-5-diethylamino phenol (5-Br-PADAP) was used as a pre-column chelating agent to form a ternary complex with Nb(V) and Ta(V) and tartaric acid. The ternary complexes of Nb(V) and Ta(V) were eluted within 8 min on a C₁₈ column with a mobile phase of methanol-water (55:45, v/v) containing 10 mmol l⁻¹ acetate buffer (pH3.5) and determined with spectrophotometric detection at 598 nm. The detection limits for Nb(V) and Ta(V) were 0.60 and 0.72 μg l⁻¹, respectively, when the ratio of signal-to-noise is 3. The proposed method was used to analyze Nb and Ta in cast iron, alloy and stainless steel.     

Determination of V(V), Nb(V) and Ta(V) as their 2-(5-nitro-2-pyridylazo)-5-diethylaminophenol complexes by reversed-phase high performance liquid chromatography

A method for the reversed-phase liquid chromatographic separation and determination of V(V), Nb(V) and Ta(V) as 2-(5-nitro-2-pyridylazo)-5 diethylaminophenol (5-NO₂-PADAP) complexes is reported. The metal complexes were eluted in 9 min with a mobile phase of methanol-water (54 : 46, v/v) containing 10 mmol L^–1 acetate buffer (pH 3.0) on an ODS column. The detection limits for V, Nb and Ta were 0.09, 0.13 and 1.41 ng mL^–1, respectively, with S/N=3. The analysis of a reference sample of a mineral is discussed. The results corresponded to the certified values, and recoveries of 98.3–101.4% have been obtained.     

Determination of V(V), Nb(V) and Ta(V) as their 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol chelates by reversed-phase HPLC

This paper reports the separation and determination of V(V), Nb(V) and Ta(V) by RP-HPLC using 5-Br-PADAP as a precolumn derivatizing reagent. On C(18) column, the three metal chelates can be separated on a baseline in 9 min with the mobile phase of methanol-water (59:41, v/v) containing tartaric acid (0.2%) and acetate buffer (pH 3.5, 10 mM). The detection limits of V(V), Nb(V) and Ta(V) are 0.13 ppb, 0.22 ppb and 1.79 ppb, respectively when S/N is 3. This method is simple and rapid, and has been used in mineral analysis with satisfactory results.     

Probing the electronic structure of early transition-metal oxide clusters: polyhedral cages of (V2O5)n(-) (n = 2-4) and (M2O5(2)(-) (M = Nb, Ta)

Vanadium oxide clusters, (V2O5)n, have been predicted to possess interesting polyhedral cage structures, which may serve as ideal molecular models for oxide surfaces and catalysts. Here we examine the electronic properties of these oxide clusters via anion photoelectron spectroscopy for (V2O5)n(-) (n = 2-4), as well as for the 4d/5d species, Nb4O10(-) and Ta4O10(-). Well-resolved photoelectron spectra have been obtained at 193 and 157 nm and used to compare with density functional calculations. Very high electron affinities and large HOMO-LUMO gaps are observed for all the (V2O5)n clusters. The HOMO-LUMO gaps of (V2O5)n, all exceeding that of the band gap of the bulk oxide, are found to increase with cluster size from n = 2-4. For the M4O10 clusters, we find that the Nb/Ta species yield similar spectra, both possessing lower electron affinities and larger HOMO-LUMO gaps relative to V4O10. The structures of the anionic and neutral clusters are optimized; the calculated electron binding energies and excitation spectra for the global minimum cage structures are in good agreement with the experiment. Evidence is also observed for the predicted trend of electron delocalization versus localization in the (V2O5)n(-) clusters. Further insights are provided pertaining to the potential chemical reactivities of the oxide clusters and properties of the bulk oxides.     

On-line preconcentration of niobium(V) and tantalum(V) as 4-(2-pyridylazo) resorcinol-citrate ternary complexes in geological samples by ion interaction high-performance liquid chromatography

4-(2-Pyridylazo) resorcinol (PAR) and citrate were used as pre-column complexing agents for the determination of Nb(V) and Ta(V) as ternary complexes in geological samples. Aliquots of 2 ml of the standard and sample solutions containing the Nb(V) and Ta(V) complexes were loaded onto a concentrator column (C18, 0.4 cm x 4.6 mm) with a carrier mobile phase comprising 20% (v/v) methanol and containing 5 mM acetic acid, 5 mM citric acid and 10 mM tetrabutylammonium bromide (TBABr), pH 6.5 at 2 ml/min for 2 min, with the effluent being directed to waste. An automatic switching valve was then switched to flush both complexes from the concentrator column onto a C18 analytical column using a mobile phase comprising 32% (v/v) methanol and containing 5 mM acetic acid, 5 mM citric acid and 3 mM TBABr, pH 6.5 for 2.5 min. The switching valve was then switched back to the original position, and cleaned with methanol for 7 min to eliminate unwanted species still adsorbed to the concentrator column. This procedure prevented later eluting compounds from reaching the analytical column, which reduced the overall run time. The detection limits of Nb(V) and Ta(V) (determined at a signal-to-noise ratio of 3, detection wavelength of 540 nm and a 2-ml sample volume) were 0.012 and 0.039 ppb for Nb(V) and Ta(V), respectively. Recoveries of Nb(V) and Ta(V) were 99.4 and 96.2%, respectively. The HPLC results obtained from the reference granite and basalt samples agreed well with inductively coupled plasma MS and certified values, but the HPLC method yielded slightly low values of the Nb/Ta ratio.     

Determination of niobium(V) and tantalum(V) as 4-(2-pyridylazo)resorcinol–citrate ternary complexes in geological materials by ion-interaction reversed-phase high-performance liquid chromatography

A method for the simultaneous separation and determination of Nb(V) and Ta(V) as ternary complexes formed with 4-(2-pyridylazo)resorcinol (PAR) and citrate was developed using ion-interaction reversed-phase high-performance liquid chromatography on a C₁₈ column. Method parameters, such as pre-column complex formation conditions and composition of the complexes were investigated using spectrophotometry and HPLC. Under the optimum conditions, the Nb(V) and Ta(V) complexes were eluted within 12 min with a mobile phase of methanol–water (32:68, v/v) containing 5 mM acetate, 5 mM TBABr and 5 mM citrate buffer at pH 6.5, with detection at 540 nm. A typical separation efficiency was 33 000 and 20 000 theoretical plates per metre for Nb(V) and Ta(V), respectively. The relative standard deviation of retention times for the Nb(V) and Ta(V) complexes were 0.16% and 0.17% and for peak areas were 0.28% and 1.36%, respectively. The detection limits (signal-to-noise ratio=3) for Nb(V) and Ta(V) were 0.4 ppb and 1.4 ppb, respectively. Results obtained for standard reference rock samples agreed well with certified values and results obtained by inductively coupled plasma MS.     

A chelating resin containing 1-(2-thiazolylazo)-2-naphthol as the functional group; synthesis and sorption behavior for trace metal ions

A new polystyrene-divinylbenzene resin containing 1-(2-thiazolylazo)-2-naphthol (TAN) functional group was synthesized and its sorption behavior for 19 metal ions including Zr(IV), Hf(IV) and U(VI) was investigated by batch and column experiments. The chelating resin showed a high sorption affinity for Zr(IV) and Hf(IV) at pH 2. Some parameters affecting the sorption of the metal ions are detailed. The breakthrough and overall capacities were measured under optimized conditions. The overall capacities of Zr(IV) and Hf(IV) that were higher than those of the other metal ions were 0.92 and 0.87 mmol/g, respectively. The elution order of metal ions at pH 4 was evaluated as: Zr(IV)>Hf(IV)>Th(IV)>V(V)>Nb(V)>Cu(II)>U(VI)>Ta(V)>Mo(VI)>Cr(III)>Sn(IV)>W(VI). Quantitative recovery of most metal ions except Zr(IV) was achieved using 2 M HNO₃. Desorption and recovery of Zr(IV) was successfully performed with 2 M HClO₄ and 2 M HCl.     

Metal-metal interactions in mixed-valence [M2Cl9]2- species: electronic structure of d1d2 (V, Nb, Ta) and d4d5 (Fe, Ru, Os) face-shared systems

The molecular and electronic structures of mixed-valence d1d2 (V, Nb, Ta) and d4d5 (Fe, Ru, Os) face-shared [M2Cl(9)]2- dimers have been calculated by density functional methods in order to investigate metal-metal bonding in this series. General similarities are observed between d1d2 and d4d5 systems and can be considered to reflect the electron-hole equivalence of the individual d1-d5 and d2-d4 configurations. The electronic structures of the dimers have been analyzed using potential energy curves for the broken-symmetry and other spin states resulting from the d1d2 and d4d5 coupling modes. In general, a spin-doublet (S = 1/2) state, characterized by delocalization of the metal-based electrons in a metal-metal bond with a formal order of 1.5, is favored in the systems containing 4d and 5d metals, namely, the Nb, Ta, Ru, and Os dimers. In contrast, the calculated ground structures for [V2Cl9]2- and [Fe2Cl9]2- correspond to a spin-quartet (S = 3/2) state involving weaker coupling between the metal centers and electron localization. In the case of [Ru2Cl9]2-, both the spin-doublet and spin-quartet states are predicted to be energetically favored suggesting that this species may exhibit double-minima behavior. A comparison of computational results across the (d1d1, d1d2, d2d2) [Nb2Cl9]z- and [Ta2Cl9]z- and (d4d4, d4d5, d5d5) [Ru2Cl9]z- and [Os2Cl9]z- series has revealed that, in all four cases, the shortening of the metal-metal distances correlates with an increase in formal metal-metal bond order.     

Determination of V(V), Nb(V), and Ta(V) with 2-(2-Thiazolylazo)-5-diethylaminophenol by Reversed-Phase High Performance Liquid Chromatography

The simultaneous determination of vanadium, niobium, and tantalum by reversed-phase high performance liquid chromatography (HPLC) with 2-(2-thiazolylazo)-5-diethylaminophenol (TADAP) as the precolumn chelating reagent has been established. Optimum conditions for the separation, such as the methanol content, the addition of tartaric acid, pH, and the concentration of acetate buffer, were investigated. The metal chelates were eluted in 8 min with a mobile phase of methanol–water (55/45, v/v) containing tartaric acid (0.1%, m/v) and acetate buffer (pH 3.5, 10 mmol/liter) on an ODS column at 568 nm. The detection limits (signal-to-noise RATIO = 3) for V(V), Nb(V), and Ta(V) were 0.16, 0.32, and 1.77 ng/ml, respectively. The proposed method was applied to the analyses of a reference of mineral and synthetic samples. The result was in accord with the certified value, and the recoveries were 98.9–101.8%.     

Heterobimetallic bismuth-transition metal salicylate complexes as molecular precursors for ferroelectric materials. Synthesis and structure of Bi(2)M(2)(sal)(4)(Hsal)(4)(OR) (4) (M = Nb,Ta; R = CH(2)CH(3), CH(CH(3))(2)), Bi(2)Ti(3)(sal)(8)(Hsal)(2), and Bi(2)Ti(4)(O(i)Pr)(sal)(10)(Hsal) (sal = O(2)CC(6)H(4)-2-O; Hsal = O(2)CC(6)H(4)-2-OH)

The reactions between triphenylbismuth, salicylic acid, and the metal alkoxides M(OCH(2)CH(3))(5) (M = Nb, Ta) or Ti[OCH(CH(3))(2)](4) have been investigated under different reaction conditions and in different stoichiometries. Six novel heterobimetallic bismuth alkoxy-carboxylate complexes have been synthesized in good yield as crystalline solids. These include Bi(2)M(2)(sal)(4)(Hsal)(4)(OR)(4) (M = Nb, Ta; R = CH(2)CH(3), CH(CH(3))(2)), Bi(2)Ti(3)(sal)(8)(Hsal)(2), and Bi(2)Ti(4)(O(i)Pr)(sal)(10)(Hsal) (sal = O(2)CC(6)H(4)-2-O; Hsal = O(2)CC(6)H(4)-2-OH). The complexes have been characterized spectroscopically and by single-crystal X-ray diffraction. Compounds of the group V transition metals contain metal ratios appropriate for precursors of ferroelectric materials. The molecules exhibit excellent solubility in common organic solvents and good stability against unwanted hydrolysis. The nature of the thermal decomposition of the complexes has been explored by thermogravimetric analysis and powder X-ray diffraction. We have shown that the complexes are converted to the corresponding oxide by heating in an oxygen atmosphere at 500 degrees C. The mass loss of the complexes, as indicated by thermogravimetric analysis, and the resulting unit cell parameters of the oxides are consistent with the formation of the desired heterobimetallic oxide. The complexes decomposed to form the bismuth-rich phases Bi(4)Ti(3)O(12) and Bi(5)Nb(3)O(15) as well as the expected oxides BiMO(4) (M = Nb, Ta) and Bi(2)Ti(4)O(11).