Use of a fritless dual tapered column and a low flow interface for capillary electrochromatography-mass spectrometry

To avoid problems associated with the use of sintered frits to retain packing material, tapered columns were investigated for use with capillary electrochromatography-mass spectrometry (CEC-MS) analysis. Taking the advantage that negatively charged stationary phase particles have a net velocity directed towards the buffer reservoir (inlet) over a wide range in pH, a fritless CEC column with a single taper tip was prepared for CEC-MS analysis. During CEC-MS analysis, the tapered end was immersed in the buffer reservoir and the unmodified end was pointed toward the ionization source. For better sensitivity, this single tapered CEC column was coupled to ESI/MS using a low flow sheath liquid interface. With this setup, occasional blockage of the ESI sprayer by stationary phase particles was observed. In addition, significant dead volume was observed because the unmodified tip could not be inserted into the very end of the sprayer of the low flow sheath liquid interface. To circumvent these problems, a dual tapered CEC column was prepared. This fritless dual tapered column CEC-MS approach alleviated the problems of frit, sprayer blockage and extensive dead volume.     

The investigation and application of the packed glass capillary column with a core

A new type of packed glass capillary column (PGCC) with a core, and its potential usage in practice are described. The permeability of the column is considerably greater than that of conventional PGCC and its N/(P_i-P_o) value is also higher. This novel PGCC column has been successfully applied to the analysis of trace levels of ethyne, cyclopropane, propadiene, propyne, and other C₁? C₄ impurities in pure ethene, propene, 1,3-butadiene, and catalytic cracking gas samples as well as other petrochemical gases such as liquified petroleum gas.     

Performance of columns packed with the new shell particles,Kinetex-C18

The performance of the new Kinetex-C₁₈ column was investigated. Packed with a new brand of porous shell particles, this column has an outstanding efficiency. Once corrected for the contribution of the instrument extra column volume, the minimum values of the reduced plate heights for a number of low molecular weight compounds (e.g., anthracene and naphtho[2,3-a]pyrene) were between 1.0 and 1.3, breaking the legendary record set 3 years ago by Halo-C₁₈ packed columns. The liquid-solid mass transfer of proteins (e.g., insulin and lyzozyme) is exceptionally fast on Kinetex-C₁₈ much faster than on the Halo-C₁₈ column. The different contributions of dispersion and mass transfer resistances to the column efficiency were determined and discussed. The possible reasons for this extremely high column efficiency are discussed.     

High performance liquid chromatographic analysis of phytoplankton pigments using a C16-amide column

In this study, a reverse-phase HPLC method incorporating a ternary solvent system was developed to analyze most polar and non-polar chlorophylls and carotenoids present in phytoplankton. The method is based on an RP-C₁₆-Amide column and provided excellent peak resolution of most taxonomically important pigments and an elution profile different than C₈ or C₁₈ columns provide. Analysis of mixed pigment standards, extracts of phytoplankton monocultures, and field samples showed that this method was able to resolve more than sixty pigments, ranging from very polar acidic chlorophylls to the non-polar hydrocarbon carotenes in less than 36 min. This included chlorophylls c₁, c₂ and c₃, divinyl chlorophylls a and b, the carotenoids lutein and zeaxanthin and some recently discovered pigments. The ability of this method to resolve divinyl chl b from monovinyl chl b and divinyl chl a from monovinyl chl a is particularly important for the quantification and identification of the marine cyanobacteria Prochlorococcus spp. in oceanic waters. The described protocol is sensitive and reproducible and can be used to assess the distribution and dynamics of major phytoplankton groups in marine and freshwater ecosystems.     

A novel method for the preparation of C18 ester-bonded RP-HPLC packings

Summary A novel procedure had been developed for the preparation of RP packings. A C₁₈ alkyl-chain was bound onto spherical silica (particle size d_p=5 μm, s=300 m²g⁻¹) with glycidoxypropyltrimethoxysilane as coupling agent. Elemental analysis, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) and chromatographic evaluation confirmed the bonding of the packings and their RP behavior.     

Reactions of chlorofullerene C60Cl6 with N-substituted piperazines

It was shown for the first time that reactions of C₆₀ halides with aliphatic amines provide a facile route for the synthesis of aminofullerenes, valuable precursors for water-soluble cationic fullerene derivatives. Particularly, chlorofullerene C₆₀Cl₆ and N-substituted piperazines were investigated in this work. It was shown that substitution of chlorine atoms in C₆₀Cl₆ by amine groups is accompanied by partial elimination of addends from the fullerene cage that yields mixtures of di-, tetra- and, hexaaminofullerenes as the final products. Separation of these mixtures by column chromatography resulted in isolation of pure 1,4-diaminofullerenes; this procedure gives much higher and more reproducible yields of these compounds than direct oxidative photoaddition of secondary amines to C₆₀. ESI mass spectrometry and NMR spectroscopy data showed that hexaaminofullerene isomers are major components in inseparable mixtures of polyaddition products. Polyaminofullerenes were found to be readily soluble in aqueous acids; these solutions are unstable because of a facile substitution of protonated amine groups with hydroxyls. Nevertheless, the use of other amine substrates in the investigated reaction can potentially allow the preparation of more stable water-soluble cationic fullerene derivatives for biological studies.     

Development of a New HPLC Method for Determination of Papaverine in Presence of Its Photooxidation Products

A new HPLC method was developed for determination of papaverine in a papaverine naturally photooxidized solution using a Duet C18/SCX column. The mobile phase used was a mixture of phosphate buffer (pH = 3.80) and acetonitrile in 40:60 ratio. The compounds identified were: papaverinol, papaveraldine, papaverine, and pyrrocolonium ion. Very good resolutions, peak shapes, and asymmetries were obtained. An ion exchange experiment was developed in order to identify and separate the pyrrocolonium ion. This was retained completely by a cation exchange resin in its Na⁺ form, while papaverine, papaverinol, and papaveraldine were retained more or less, due to a retention explained by a combined ion exchange-solvent extraction mechanism. Voltammetric studies showed that natural photooxidation of papaverine occurs in three irreversible steps and yields to stable compounds in solution.     

Hydration of C3a in the presence of CaCO3

The hydration of C₃A with and without CaCO₃ was studied. The techniques used were X-ray diffraction, thermogravimetry, differential thermogravimetry and calorimetry.In the presence of CaCO₃, the hydration of C₃A is accelerated. The hexagonal hydrates are formed first. They react with CaCO₃ to form calcium carboaluminate hydrate. This reaction blocks formation of the cubic hydrate. The latter appears when CaCO₃ is completely consumed.     

DFT study of structural, electronic, vibrational, and magnetic properties of the chirality cage-like molecule C24O12

Bonding, vibrational and magnetic properties of the cage-like molecule C(24)O(12) are studied by DFT calculations. Infrared- and Raman-active vibrational frequencies of the cage-like molecule C(24)O(12) are assigned. Two (13)C and one (17)O nuclear magnetic resonance (NMR) spectral signals of the cage-like molecule C(24)O(12) are characterized. Heat of formation of the cage-like molecule C(24)O(12) is estimated. Compared to C(60) and the cage-like molecule C(24)O(12), only from the thermodynamic points of view, C(24)O(12) is more stable than C(60). Thus we believe that the cage-like molecule C(24)O(12) has sufficient stability to allow its experimental preparation. We proposed that it could be synthesized by using the condensation of molecules C(6)(OH)(6) and C(12)Cl(12). Since the symmetry of C(24)O(12) is D(6), it is a chiral molecule.     

Improving analysis of apolar organic compounds by the use of a capillary titania-based column: Application to the direct determination of faecal sterols cholesterol and coprostanol in wastewater samples

This article reports a new procedure for the direct determination of faecal sterols coprostanol and cholesterol in wastewater samples as tracers of human sewage contamination. The method combines in-tube solid-phase microextraction (IT-SPME) for analyte enrichment and capillary liquid chromatography (LC) for separation with diode array detection for identification and quantification. A titania-based polymeric capillary column and a conventional octadecyl silica (ODS) capillary column were evaluated and compared for their ability to separate the analytes. The titania-based column allowed the separation of the analytes in much shorter chromatographic times and with better chromatographic profiles, which in turn resulted in better detectability. In addition, IT-SPME allowed the direct injection into the chromatographic system of sample volumes as large as 200 μL, thus making unnecessary off-line clean-up and concentration steps. In such a way, the tested compounds could be directly analysed in less than 10 min, the limits of detection (LODs) being 10 and 1.2 μg/L for coprostanol and cholesterol, respectively. The reliability of the proposed method was tested by processing several wastewater samples.     

带喷头混合型毛细管色谱柱的制备及其在蛋白质组分离分析中的应用

本研究制备了一种应用于液-质联用（LC-MS）系统中的带喷头混合型毛细管色谱柱．用标准蛋白和酵母蛋白胰蛋白酶酶切溶液考察了其在LC—MS中的离子化效率、毛细管色谱柱分离性能和寿命,并与直接填充型毛细管色谱柱的色谱性能进行比较,未见显著性差异．将制备的带喷头混合型毛细管色谱柱应用于鼠肝蛋白组的分析,在假阳性率为1％的条件下鉴定到1262个肽段,归属于513个蛋白簇．通过对鉴定蛋白质理化性能的统计分析,其等电点和分子量分布高于一般两维凝胶电泳的范围．实验结果还表明该混合型毛细管色谱柱在肽段的理化性能上没有偏性,可以广泛应用于蛋白质组学的研究中．     

纳米金聚集复合物放大的计时电位法测定补体C3

报道了一种用金标复合物放大的计时电位法测定补体C3的电化学免疫检测方法.对影响传感器响应的因素如蛋白A固定浓度、抗体包被过程的pH及浓度、金标物混合比等进行了考察.在优化的实验条件下,传感器的信号响应和补体C3的浓度在0.12～117.3 ng/mL范围内具有良好的线性关系,检出限达0.02 ng/mL.     

Solid-phase microextraction using octadecyl-bonded silica immobilized on the surface of a rotating disk: Determination of hexachlorobenzene in water

Solid-phase microextraction of hexachlorobenzene from water was implemented for the first time on a rotating disk coated with an octadecyl-bonded silica (C₁₈) sorptive phase. The results indicate that the sorption performance of this phase for the model analyte selected is similar to that observed using a rotating disk containing PDMS. In both cases, equilibrium is achieved within approximately 120 min for samples volumes of 50 mL and decreases to 20–30 min when the sample volume is decreased to 10 mL. The comparable behavior observed for the sorption of HCB in both phases is consistent with a similar rate-determining step for extraction, which suggests that the overall mass transfer of analyte is not limited by internal diffusion into the phase but by diffusion into the aqueous stagnant layer. The main advantage in the use of the C₁₈ phase is that the elution of the analyte was achieved in 15 min compared with 45 min for PDMS because, in the case of C₁₈, dichloromethane can be used as the eluting solvent.     

Development of a gel monolithic column polydimethylsiloxane microfluidic device for rapid electrophoresis separation

A β-cyclodextrin (β-CD)-bonded gel monolithic column polydimethylsiloxane (PDMS) microfluidic device was developed in a simple and feasible way. Before preparation of gel monolithic column in PDMS microchannel, PDMS surface was activated by UV light to create silanol groups, which is an active molecule to covalently bond 3-(trimethoxysilyl)-propyl methacrylate (Bind-Silane) and seal microfluidic device. By the way, Bind-Silane is a bifunctional molecule to link polyacrylamide (PAA) gel and inner wall of PDMS microchannel covalently. Allyl-β-CD was used not only as a multifunctional crosslinker in PAA gel to control the size of the pores, but also as a chiral selector for the enantioseparation. The stability, transferring heat and optical characteristic of the microfluidic device were examined. The separation capability of the gel monolithic column was confirmed by the successful separation of fluorescein isothiocyanate (FITC)-labeled arginine (Arg), glutamine acid (Glu), tryptophan (Try), cysteine (Cysteine) and phenylalanine (Phe) in the PDMS microfluidic device less than 100 s at 36 mm effective separation length. A maximum of 2.06 × 10⁵ theoretical plates was obtained by the potential strength of 490 V/cm. A pair of FITC-labeled dansyl-d,l-threonine (Dns-Thr) was separated absolutely.     

Development of a disulfiram-modified human serum albumin-based HPLC column

Summary A human serum albumin (HSA)-based HPLC column has been modified in situ by disulfiram, an alcohol-deterrent drug reported to bind cys₃₄, the only free cysteine in HSA, under physiological conditions. The reversible and covalent binding of disulfiram was found to change the binding properties of the protein, giving rise to a new selector which performed differently from the native albumin-based stationary phase. When low concentrations of disulfiram were used as mobile phase modifier, reversible binding resulted in a cooperative allosteric effect with improved selector performance. Covalent modification resulted in markedly reduced affinity for binding of the drugs to sites I or II, while still maintaining enantioselectivity. This study has enabled the monitoring of interactions of disulfiram with potentially coadministered drugs, and the preparation of a chiral selector with different drug affinity and enantioselectivity.     

Thermochemistry of C60 and C70 fullerene solvates

In an effort to improve understanding of dissolution behaviour of fullerenes and their simple chemical derivatives the binary systems of C₆₀, C₇₀ and the piperazine monoadduct of [60] fullerene C₆₀ N₂C₄H₈ with a series of aromatic solvents have been studied by means of DSC. In certain systems solid solvates have been found to be the thermodynamically stable phases relative to saturated solution at room temperature. Identified solid solvates were characterized by their compositions, temperatures and enthalpies of incongruent melting transitions. The regularities in thermodynamic stability of the solvated crystals have been discussed along with dissolution properties of fullerenes and the derivative. Certain correlations have been observed.     

A column packing for isothermal gas chromatographic analysis of C1−C5 paraffins and monoolefins and dimethyl ether

Summary An analytical GC method was developed which uses a single packed column consisting of three packings in series prepared with the following liquid phases: dimethyl sulfolane, propylene carbonate, and silver nitrate. This system provides satisfactory resolution of mixtures of C₁–C₅ hydrocarbons and dimethyl ether obtained when converting methanol to gasoline. Due to the high capacity of the column it is possible to inject larger sample amounts permitting trace analysis.     

Crystal growth of Ln3GaO6 (Ln = Nd, Sm, Eu and Gd): Structural and optical properties

Single crystals of Ln₃GaO₆ (Ln = Nd, Sm, Eu, Gd) were grown out of a reactive high temperature hydroxide melt. The structures were solved by single-crystal X-ray diffraction. These gallium oxides crystallize in the polar space group Cmc2₁ where the orientation of the GaO₄ tetrahedra determines the polarity of the structure. The atomic positions along with the determination of the absolute structure are reported. The lanthanide atoms are located in a seven-fold coordination environment forming edge-sharing zigzag-chains. The photoluminescence was investigated and the europium and gadolinium members of this series exhibit intense luminescence in the visible portion of the spectrum.