Capillary liquid chromatographic-high-resolution mass spectrometric analysis of ribonucleotides

A method of capillary HPLC-high-resolution MS was developed for the trace analysis of ATP, GTP, dATP and dGTP Dimethylhexylamine (DMHA) was used as ion-pairing agent for the HPLC retention and separation of the nucleotides and positive ion electrospray time-of-flight MS was used for the detection. The application of capillary HPLC allowed minimal usage of DMHA while providing excellent peak retention and resolution, which significantly reduced the ion suppression in electrospray ionization-MS analysis and thus increased the sensitivity. Adduct ions of nucleotides and DMHA were used as quantitative ions in order to achieve the best sensitivity. DMHA concentration at 5 mM in the aqueous mobile phase at pH 7 was found to be the optimal conditions for the C Is capillary column. The method was applied to determine ATP level in cultured C6 glioma cells that were treated with toxic concentrations of Zn. The results showed that the cellular ATP level decreased from 2.7 pmol/cell (<10% cell death) in average control cell samples to 0.36 pmol/cell as the concentration of Zn increased to 120 mg/l (>35% cell death) in culture medium.

Preparation of polymer/silica nanoscale hybrids through sol-gel method involving emulsion polymers. II. Poly(ethyl acrylate)/SiO2

Poly(ethyl acrylate) (PEA)/SiO2 hybrids with different compositions were prepared under different casting temperatures and pH values. Their morphology as investigated by transmission electron microscopy (TEM) shows that samples with different compositions have different morphologies. When the SiO2 content is lower, PEA is the continuous phase and SiO2 is the dispersed phase. At higher SiO2 content, the change in phase morphology takes place, nd PEA gradually dispersing in the form of latex particles in SiO2 matrix. Change in phase morphology depends mainly on the time the sol-gel transition occurs. At suitable casting temperature and pH value, PEA/SiO2 in 95/5 and 50/50 hybrids with even dispersion was obtained.

Hybrid luminescent films obtained by covalent anchoring terbium complex to silica-based network

New monomer N-(4-carboxyphenyl)-NL-(propyltriethoxysilyl)urea (1) which acts as both a ligand for Th3+ ion and a sol-gel precursor has been synthesized and characterized by H-1 NMR, and MS. Hybrid luminescent thin films consisting of organoterbium covalently bonded to a silica-based network have been obtained in situ via a sol-gel approach. Strong line emission of Tb3+ ion was observed from the hybrid luminescent films under UV excitation.

Capillary electrophoresis with electrochemiluminescence detection of procyclidine in human urine pretreated by ion-exchange cartridge

This paper describe a Ru(bpy)(3)(2+) based electrochemiluminescence (ECL) method to detect procyclidine in human urine following separation by capillary electrophoresis (CE). An ECL detection cell was designed for post-column addition of Ru(bpy)(3)(2+). Parameters affecting separation and detection were optimized, leading to a detection limit of 1 x 10(-9) mol/l in an on-capillary stacking mode. For application in urine, a cartridge packed with slightly acidic cation-exchange resin was used to eliminate the matrix effects of urine and improve the detection sensitivity. Extraction recovery was nearly 90%.

Preparation and luminescence properties of hybrid materials containing europium(III) complexes covalently bonded to a silica matrix

A new kind of luminescent organic-inorganic hybrid material (denoted Hybrid I) consisting of europium 1,10-phenanthroline complexes covalently attached to a silica-based network was prepared by a sol-gel process. 1,10-Phenanthroline grafted to 3-(triethoxysilyl)propyl isocyanate was used as one of the precursors for the preparation of an organic-inorganic hybrid materials. For comparison purposes, the hybrid material (denoted Hybrid II) in which phenanthroline was not grafted onto the silica backbone of the frameworks was also prepared. Elemental analysis; NMR, FT-IR, UV/vis absorption, and luminescence spectroscopies, and luminescence decay analysis were used to characterize the obtained hybrid materials. It is shown that the homogeneity of Hybrid I is superior to that of Hybrid II, and a higher concentration europium can be incorporated into Hybrid I than Hybrid II. Excitation at the ligand absorption wavelength (283 nm) resulted in the strong emission of the Eu3+ D-5(0)-F-7(J) (J = 0-4) transition lines as a result of the efficient energy transfer from the ligands to the EU3+ in Hybrid I. The number of water molecules coordinated to the europium ion was estimated, and the structure of the as-synthesized Hybrid I was predicted on the basis of the experimental results.

Capillary electrophoresis with amperometric detection of curcumin in Chinese herbal medicine pretreated by solid-phase extraction

In the present study, curcumin from Chinese herbal medicine turmeric was determined by capillary electrophoresis with amperometric detection (CE-AD) pretreated by a self-designed, simple, inexpensive solid-phase extraction (SPE) cartridge based on the material of tributyl phosphate resin. An average concentration factor of 9 with the recovery of >80% was achieved when applied to the analysis of curcumin in extracts of turmeric. Under the optimized CE-AD conditions: a running buffer composed of 15 mM phosphate buffer at a pH 9.7, separation voltage at 16 W, injection for 6 s at 9 W and detection at 1.20 V, CE-AD with SPE exhibited low detection limit as 3 - 10(-8) mol/l (SIN = 3), high efficiency of 1.0(.)10(5) N, linear range of 7(.)10(-4) -3(.)10(-6) mol/l (r = 0.9986) for curcumin extracted from light petroleum. The method developed resulted in enhancement of the detection sensitivity and reduction of interference from sample matrix in complicated samples and exhibited the potential application for routine analysis, especially in food, because a relatively complete process of sample treatment and analysis was described.

Electrochemiluminescence of tris(2,2 '-bipyridyl)ruthenium (II) ion-exchanged in polyelectrolyte-silica composite thin-films

The organic-inorganic hybrid, PSS-silica composite material was developed for the immobilization of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) on glassy carbon electrode via ion-exchange (PSS stands for poly(sodium 4-styrene-sulfonate)). The electrochemiluminescence (ECL) and electrochemistry of Ru(bpy)(3)(2-) immobilized in the composite thin films have been investigated with tripropylamine (TPA) as the coreactant. The immobilized Ru(bpy)(3)(2-) underwent a surface process. The modified electrode was used for the ECL detection of TPA and showed high sensitivity. Detection limit was 0,1 mumol L-1 for TPA (S/N = 3) with a linear range from 0.5 mumol L-1 to 5 mmol L-1 (R = 0.998), Moreover, the resulting modified electrode was stable over six months and the good stability may be due to the strong interaction between Ru(bpy)(3)(2-) and the high ion-exchange able PSS-silica composite films on GCE. Compared with other materials. the PSS-silica composite films containing incorporated Ru(bpy)(3)(2-) showed improved sensitivity and long-term stability, Thus, such composite thin film can be a promising material for the construction of ECL sensor.

Progress in amperometric detection for capillary electrophoresis

As a high efficiency separation technique, capillary electrophoresis(CE) has been widely used in various fields of analytical science. Amperometry is one of the most sensitive electrochemical detection methods in CE. The capillary/electrode decoupling mechanism, applications,of new electrode systems in CE, detection cell technique are discussed in detail. Amperometric detection is compatible with microfabricated CE chips and will make the concept of lab-on-a-chip become a reality. Because of these progresses, amperometry is becoming a widely acceptable detection method,for more chemical and biological analytes.

Preparation of polymer/silica nanoscale hybrids through sol-gel method involving emulsion polymers (PMMA/SiO2)

The different poly (methyl methacrylate) (PMMA) /SiO2 hybrids were prepared through sol-gel method involving PMMA emulsion (emulsion method) and PMMA/THF solution (solution method). The samples were characterized by differential scanning calorimetry(DSC), thermogravimetry analysis(TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that PMMA/SiO2 composites in nanoscale were prepared by emulsion method, and its size of phase heterogeneity was less than that of solution method. Meanwhile, the polymer emulsion as the reactive medium was more suitable for the formation of SiO2 network.

Polymer/silica nanoscale hybrids through sol-gel method involving emulsion polymers. 1. Morphology of poly(butyl methacrylate)/SiO2

In this article, we report on an approach of using an emulsion polymerized polymer in preparing organic-inorganic nanocomposites through a sol-gel technique. By mixing a polymer emulsion with prehydrolyzed tetraethoxysilane transparent poly(butyl methacrylate)/SiO2, nanocomposites were prepared as shown by TEM. AFM, FTIR, and XPS results show that there is a strong interaction between polymer latex particles and the SiO2 network. Comparison of the emulsion method with a traditional solution method shows that nanocomposites can be prepared by both methods, but there is some difference in their morphology and properties.

Determination of three beta-blockers by capillary electrophoresis with end-column electrochemical detection

Three beta -blockers (propranolol, timolol, acebutolol) were separated by capillary electrophoresis (CE) and detected by end-column electrochemical detection (EC). In the present work, a carbon fiber (33 mum) electrode was used as the working electrode. The effect of the buffer concentration, buffer pH, detection potential and separation voltage on the separation of analytes and behavior of electrochemical detection was systematically investigated. The optimum conditions determined were as following: 40 cm length, 25 mum i.d. capillary; 17.5 kV separation voltage; 2 s injection at 15 kV; 70mM phosphate buffer, pH 3.5; detection potential + 1.2V (vs. Ag/AgCl). Under these conditions, the linear ranges of beta -blockers were over three orders of magnititude and the low detection limit of 10(-8)M was obtained. This method was also applied to detect the simulated urine sample.

Silica sol-gel composite film as an encapsulation matrix for the construction of an amperometric tyrosinase-based biosensor

An amperometric tyrosinase enzyme electrode for the determination of phenols was developed by a simple and effective immobilization method using sol-gel techniques. A grafting copolymer was introduced into sol-gel solution and the composition of the resultant organic-inorganic composite material was optimized, the tyrosinase retained its activity in the sol-gel thin film and its response to several phenol compounds was determined at 0 mV vs. Ag/AgCl (sat. KCI). The dependences of the current response on pH, oxygen level and temperature were studied, and the stability of the biosensor was also evaluated. The sensitivity of the biosensor for catechol, phenol and p-cresol was 59.6, 23.1 and 39.4 muA/mM, respectively. The enzyme electrode maintained 73% of its original activity after intermittent use for three weeks when storing in a dry state at 4 degreesC. (C) 2000 Elsevier Science S.A. All rights reserved.

Tunable photoluminescence in sol-gel derived silica xerogels

Silica xerogels prepared by sol-gel method show blue emission under UV excitation with a smaller Stokes shift. The luminescent properties have been investigated under various preparation conditions and compositions. The silica xerogels show similar luminescent properties when using C2H5OH and N,N-dimethylformamide (DMF) as solvents, which are very different from those when using dimethylsulfoxide (DMSO) as solvent, i.e., a red shift of excitation and emission has been observed in the latter case. The emission intensity of the silica xerogels also depends on the water content and pH of the starting reaction solution. The introduction of organic group (-CH3) in the silica xerogel modifies the network structure and further changes their luminescence properties. Heat treatment results in the decomposition of the organic (-SiCH3) groups, which eliminates the old luminescent centers and produces new luminescent centers in longer wavelength simultaneously. (C) 2000 Elsevier Science B.V. All rights reserved.

In situ synthesis of terbium-benzoic acid complex in sol-gel derived silica by a two-step sol-gel method

Terbium complexes with benzoic acid and its derivatives o-hydroxybenzoic acid and p-hydroxybenzoic acid were in situ synthesized in sol-gel derived silica matrix via a two-step sol-gel process. The formation process of the complex was characterized by fluorescence spectra, absorption spectra and IR spectra. The gels that contain in situ synthesized complexes exhibit the characteristic emission bands of terbium ion. The fluorescence lifetimes of Tb3+ in the silica gels are longer than those in the pure complexes and in the solutions that contain the corresponding complexes. (C) 2000 Elsevier Science Ltd. All rights reserved.

Simultaneous determination of 2-aminothiazole, 2-aminobenzothiazole and 2-mercaptobenzothiazole by capillary electrophoresis with end-column amperometric detection

Capillary electrophoresis with amperometric detection is evaluated for the simultaneous determination of 2-aminothiazole (A), 2-amino-benzothiazole (AB), 2-mercaptobenzothiazole (AM). The cyclic voltammogram, hydrodynamic voltammogram, effect of pH, concentration of buffer and separation voltage on the separation and the detection were studied. The conditions were optimized as follows: 50 mM phosphate buffet; pH 6.0, 2s at 17.5 kV sample injection, separation at 17.5 kV, 1.2 V as detection potential. The method provided low detection limit as 0.5 mu M, 0.05 mu M and 0.01 mu M, wide linear range 2-200 mu M, 10-200 mu M and 0.025-100 mu M for A, AB, and AM, respectively. The variations in peak current and migration time for 15 consecutive injections of a standard containing 5 mu M each compound were 3.7, 2.1, and 3.9%, and 1.2, 0.8, and 1.2%, for A, AB and AM, respectively. This method was employed to analyze river water.