Determination of arsenic species by capillary zone electrophoresis with large-volume field-amplified stacking injection

Determination of arsenic species by large-volume field amplified stacking injection-capillary zone electrophoresis (LV-FASI-CZE) is reported in this paper. Whole column injection was employed. The optimum buffer pH for the separation of weak acids was discussed. It was found that the optimum buffer to analyze the stacked arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) was 25 mm phosphate at pH 6.5. However, the optimum buffer to analyze the concentrated arsenite (As(III)) was 20 mm phosphate - 10 mm borate at pH 9.28. The limits of detection of the method developed were 0.026 mg/L for As(III), 0.023 mg/L for As(V), 0.043 mg/L for MMA, and 0.018 mg/L for DMA. An enrichment factor of 34-100 for several arsenic species was obtained. In the end, this method was applied to determine the arsenic concentration in the environmental reference materials to show the usefulness of the method developed.

Profiling of Complex Microbial Populations by Denaturing Gradient Gel Electrophoresis Analysis of Polymerase Chain Reaction-Amplified Genes Coding for 16S rRNA

We describe a new molecular approach to analyzing the genetic diversity of complex microbial populations. This technique is based on the separation of polymerase chain reaction-amplified fragments of genes coding for 16S rRNA, all the same length, by denaturing gradient gel electrophoresis (DGGE). DGGE analysis of different microbial communities demonstrated the presence of up to 10 distinguishable bands in the separation pattern, which were most likely derived from as many different species constituting these populations, and thereby generated a DGGE profile of the populations. We showed that it is possible to identify constituents which represent only 1% of the total population. With an oligonucleotide probe specific for the V3 region of 16S rRNA of sulfate-reducing bacteria, particular DNA fragments from some of the microbial populations could be identified by hybridization analysis. Analysis of the genomic DNA from a bacterial biofilm grown under aerobic conditions suggests that sulfate-reducing bacteria, despite their anaerobicity, were present in this environment. The results we obtained demonstrate that this technique will contribute to our understanding of the genetic diversity of uncharacterized microbial populations.

Soil microbial community analysis using denaturing gradient gel electrophoresis

The most biological diversity on this planet is probably harbored in soils. Understanding the diversity and function of the microbiological component of soil poses great challenges that are being overcome by the application of molecular biological approaches. This review covers one of many approaches being used: separation of polymerase chain reaction (PCR) amplicons using denaturing gradient gel electrophoresis (DGGE). Extraction of nucleic acids directly from soils allows the examination of a community without the limitation posed by cultivation. Polymerase chain reaction provides a means to increase the numbers of a target for its detection on gels. Using the rRNA genes as a target for PCR provides phylogenetic information on populations comprising communities. Fingerprints produced by this method have allowed spatial and temporal comparisons of soil communities within and between locations or among treatments. Numerous samples can be compared because of the rapid high throughput nature of this method. Scientists now have the means to begin addressing complex ecological questions about the spatial, temporal, and nutritional interactions faced by microbes in the soil environment.

Direct electrochemical detection of glucose in human plasma on capillary electrophoresis microchips

We developed an electrochemical detector on a hybrid chip for the determination of glucose in human plasma. The microchip system described in this paper consists of a poly(dimethylsiloxane) (PDMS) layer containing separation and injection channels and an electrode plate. The copper microelectrode is fabricated by selective electroless deposition. The fabrication of the decoupler is performed by platinum electrochemical deposition on the metal film formed by electroless deposition. Factors influencing the performance, including detection potential, separation field strength, and buffer concentration, were studied. The electrodes exhibited good stability and durability in the analytical procedures. Under optimized detection conditions, glucose responded linearly from 10 muM to 1 mM. Finally, glucose in human plasma from three healthy individuals and two diabetics was successfully determined, giving a good prospect for a new clinical diagnostic instrument.

Field-amplified sample stacking capillary electrophoresis with electrochemiluminescence applied to the determination of illicit drugs on banknotes

Capillary electrophoresis (CE) with Ru(bpy)(3)(2+) electrochemiluminescence. (ECL) detection system was established to the determination of contamination of banknotes with controlled drugs and a high efficiency on-column field-amplified sample stacking (FASS) technique was also optimized to increase the ECL intensity. The method was illustrated using heroin and cocaine, which are two typical and popular illicit drugs. Highest sample stacking was obtained when 0.01 mM acetic acid was chosen for sample dissolution with electrokinetical injection for 6 s at 17 kV. Under the optimized conditions: ECL detection at 1.2 V, separation voltage 10.0 kV, 20 mM phosphate-acetate (pH 7.2) as running buffer, 5 mM Ru(bpy)(3)(2+) with 50 mM phosphate-acetate (pH 7.2) in the detection cell, the standard curves were linear in the range of 7.50 x 10(-8) to 1.00 x 10(-5) M for heroin and 2.50 x 10(-7) to 1.00 x 10(-4) M for cocaine and detection limits of 50 nM for heroin and 60 nM for cocaine were achieved (S/N = 3), respectively. Relative standard derivations of the ECL intensity and the migration time were 3.50 and 0.51% for heroin and 4.44 and 0.12% for cocaine, respectively.The developed method was successfully applied to the determination of heroin and cocaine on illicit drug contaminated banknotes without any damage of the paper currency.

Application of matrix-assisted laser desorption/ionization-time of flight-mass spectrometry and sodium dodecyl sulfate-polyacrylamide gel electrophoresis in determining arginine esterase from snake venom

Using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The homogeneities and molecular weights of three arginine esterases from snake venom, which possessing therapeutic use in myocardial infarction, were determined and compared, MALDI-TOF-MS is possessed of high accuracy, high sensitivity and rapidity. MALDI-TOF-MS and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) can provide complementary and confirmatory results information. MALDI-TOF-MS can be directly used as an important method for the purification of snake venom complexes successfully.

Determination of heavy metal ions by capillary electrophoresis with contactless conductivity detection after field-amplified sample injection

A method has been developed for determining of heavy metal ions by field-amplified sample injection capillary electrophoresis with contactless conductivity detection. The effects of the 2-N-morpholinoethanesulfonic acid/histidine (MES/His) concentration in the sample matrix, the injection time and organic additives on the enrichment factor were studied. The results showed that MES/His with a low concentration in the sample matrix, an increase of the injection time and the addition of acetonitrile improved the enrichment factor. Four heavy metal ions (Zn2+, Co2+, Cu2+ and Ni2+) were dissolved in deionized water, separated in a 10 mM MES/His running buffer at pH 4.9 and detected by contactless conductivity detection. The detection sensitivity was enhanced by about three orders of magnitude with respect to the non-stacking injection mode. The limits of detection were in the range from 5 nM (Zn2+) to 30 nM (Cu2+). The method has been used to determine heavy metal ions in tap water.

Principles of flow field diagnostics by laser-induced biacetyl phosphorescence

A new method for measuring the density, temperature and velocity of N2 gas flow by laser induced biacetyl phosphorescence is proposed. The characteristics of the laser induced phosphorescence of biacetyl mixed with N2 are investigated both in static gas and in one-dimensional flow along a pipe with constant cross section. The theoretical and experimental investigations show that the temperature and density of N2 gas flow could be measured by observing the phosphorescence lifetime and initial intensity of biacetyl triplet (3Au) respectively. The velocity could be measured by observing the time-of-flight of the phosphorescent gas after pulsed laser excitation. The prospect of this method is also discussed.

Numerical Simulation of Pulsed Laser Transformation Hardening

A novel pulsed laser surface processing technology is introduced, which can make use of the spatial and temporal profile of laser pulse to obtain ideal hardening parameters. The intensity distribution of laser pulse is spatially and temporally controlled by using laser shape transformation technology. A 3D numerical model including multi-phase transformations is established to explore material microstructure evolution induced by temperature field evolution. The influences of laser spatial-temporal profiles on hardening parameters are investigated. Different from the continuous laser processing technology, results indicate that spatial and temporal profiles are important factors in determining processing quality during pulsed laser processing method.

Structural and optical properties of YAG : Ce3+ phosphors by sol-gel combustion method

High-quality Ce3+-doped Y3Al5O12 (YAG:Ce3+) phosphors were synthesized by a facile sol-gel combustion method. In this sol-gel combustion process, citric acid acts as a fuel for combustion, traps the constituent cations and reduces the diffusion length of the precursors. The XRD and FT-IR results show that YAG phase can form through sintering at 900 degrees C for 2 h. This temperature is much lower than that required to synthesize YAG phase via the solid-state reaction method. There were no intermediate phases such as YAlO3 (YAP) and Y4Al2O9 (YAM) observed in the sintering process. The average grain size of the phosphors sintered at 900-1100 degrees C is about 40 nm. With the increasing of sintering temperature, the emission intensity increases due to the improved crystalline and homogeneous distribution of Ce3+ ions. A blue shift has been observed in the Ce3+ emission spectrum of YAG:Ce3+ phosphors with increasing sintering temperatures from 900 to 1200 degrees C. It can be explained that the decrease of lattice constant affects the crystal field around Ce3+ ions. The emission intensity of 0.06Ce-doped YAG phosphors is much higher than that of the 0.04Ce and 0.02Ce ones. The red-shift at higher Ce3+ concentrations may be Ce-Ce interactions or variations in the unit cell parameters between YAG:Ce3+ and YAG. It can be concluded that the sol-gel combustion synthesis method provides a good distribution of Ce3+ activators at the molecular level in YAG matrix. (c) 2005 Elsevier B.V. All rights reserved.