JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2007
Marie-Françoise Nonier
Abstract The reactions between (+)-catechin and representative oak wood furanic (furfuraldehyde, 5-hydroxymethylfurfuraldehyde and 5-methylfurfuraldehyde) and phenolic (vanillin and syringaldehyde) aldehydes in a wine-like model solution were studied and the corresponding condensation kinetics at pH 3.0 and 3.5 were compared. A comparative study on the reactivity of these two representative families of aldehydes towards (+)-catechin showed a large difference between them. When incubated separately with (+)-catechin at both pH values, the reactions were faster with furanic aldehydes than with phenolic aldehydes. In mixtures containing (+)-catechin and individual aldehydes, new compounds were identified by high-performance liquid chromatography (HPLC)/UV,visible detection, some of which were characterised by liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS). The increase in solution absorbance with time was closely linked to these new products. Copyright © 2007 Society of Chemical Industry [source]

High-throughput screening of kinase inhibitors by multiplex capillary electrophoresis with UV absorption detection

ELECTROPHORESIS, Issue 1-2 2003
Yan He
Abstract Protein kinases play a major role in the transformation of cells and are often used as molecular targets for the new generation of anticancer drugs. We present a novel technique for high-throughput screening of inhibitors of protein kinases. The technique involves the use of multiplexed capillary electrophoresis (CE) for the rapid separation of the peptides, phosphopeptides, and various inhibitors. By means of UV detection, diversified peptides with native amino acid sequences and their phosphorylated counterparts can be directly analyzed without the need for radioactive or fluorescence labeling. The effects of different inhibitors and their IC50 value were determined using three different situations involving the use of a single purified kinase, two purified kinases, and crude cell extracts, respectively. The results suggest that multiplexed CE/UV may prove to be a straightforward and general approach for high-throughput screening of compound libraries to find potent and selective inhibitors of the various protein kinases. [source]

Use of various processes for pilot plant treatment of wastewater from a wood-processing factory

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2001
Nikolaos S Athanasopoulos
Abstract The wastewater from a wood-processing factory is characterized by a high COD, chlorides and nitrogen content. Various treatment processes were applied to treat this wastewater in pilot-scale units. By applying one-stage denitrification,activated sludge biological treatment it was not possible to remove nitrogen. Nitrification was inhibited by wastewater compounds. By applying a second stage of a nitrification biofilter it was possible to have a high degree of nitrification. The denitrification was complete. With biological methods the reduction of COD, and -N and -N concentrations to acceptable values was not achievable. Physical,Chemical methods as H2O2/UV, electrolysis and ozonation were used as post-treatment of effluents from the biological system. Radical degradation, initiated by the powerful hydroxyl radicals which are generated from H2O2 by UV activation, is used for wastewater post-treatment. The combination of H2O2/UV was not suitable for post-treatment of this wastewater. With electrolysis, -N and COD removal can be complete. The total amount of ammonia and organic nitrogen converted to nitrate nitrogen for current density of 1.15,Adm,2 and energy consumption of 71.6,kWhm,3 was 0.35,gdm,3. Further biological denitrification is required for -N removal to permitted values. Energy consumption for the elimination of 1,kg COD was 40.4,kWh and 35.8,kWh for current densities of 0.7,Adm,2 and 1.15,Adm,2 respectively. The energy required to reach the limit value of COD equal to 150,mgdm,3 for current density of 1.15,Adm,2 was 71.6,kWhm,3. With ozonation, the COD removal can be complete. Further biological nitrification,denitrification is required to remove -N and -N to permitted values. At pH 7.0, in order to reach the limit value of COD equal to 150,mgdm,3, specific ozone dose was 6.0,g per g of COD removed and the total amount of ammonia and organic nitrogen converted to nitrate nitrogen was 0.25,gdm,3. The total equivalent energy required is estimated to be 75.0,kWhm,3. © 2001 Society of Chemical Industry [source]

Dosage de l'octyl dimethyl PABA, de l'homosalate et de l'octyl salicylate dans les produits de protection solaire

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2001
M.-O. Masse
Résumé La méthode décrit le dosage de l,octyl dimethyl PABA (2-ethylhexyl 4-(dimethylamino)benzoate) (CAS RN 21245-02-3), de l,homo-salate (3,3,5-trimethylcyclohexyl salicylate) (CAS RN 118-56-9) et de l,octyl salicylate (2-ethylhexyl salicylate) (CAS RN 118-60-5) dans les produits cosmétiques de protection solaire. L,échantillon est mis en suspension dans le méthanol et après traitement approprié, le dosage est effectué par HPLC/UV. La précision, le rendement et la fiabilité de la méthode ont été déterminés. Synopsis The method describes the quantitative determination of octyl dimethyl PABA (2-ethylhexyl 4- (dimethylamino)benzoate) (CAS RN 21245-02-3), homosalate (3,3,5-trimethylcyclohexyl salicylate) (CAS RN 118-56-9) and octyl salicylate (2-ethylhexyl salicylate) (CAS RN 118-60-5) in cosmetic sunscreen products. The sample is suspended in methanol and after appropriate treatment the determination is made by HPLC/UV. Accuracy, yield and viability of the method were resolved. [source]

Switching from HPLC/UV to MEIA for whole blood sirolimus quantitation: comparison of methods

JOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 6 2006
Luigi Alberto Pini
Abstract Sirolimus is a immunosuppressive agent for renal transplant recipients. Monitoring of whole blood sirolimus concentration is necessary in order to improve clinical outcomes. An increasing number of clinical laboratories (4,14% during 2005) are using microparticle enzyme immunoassay (MEIA) for sirolimus quantitation but previous reports indicated a high variability, with a mean difference of 17% for MEIA method vs. high-performance liquid chromatography/ultraviolet (HPLC/UV). This study was aimed at comparing the reliability of MEIA with the HPLC/UV method. Blood samples from transplant patients were processed using both HPLC/UV and MEIA assays. Comparison and Bland-Altman plots, as well as regression analysis and paired t -test were used to compare results of the assays. Concentrations were stratified into three groups and used to investigate whether any observed difference between methods could be influenced by sirolimus concentration. Regression analysis yielded a coefficient of correlation R of 0.9756, the line of best fit being y=0.9832x+0.1976. The statistical analysis showed no difference between the two sets of experimental data. The average percentage difference between the two methods was found to be ,0.2±19.2%. On the basis of our present results, the tested MEIA assay is able to quantify sirolimus concentration with a clinically acceptable imprecision, similar to that of HPLC/UV method. J. Clin. Lab. Anal. 20:239,244, 2006. © 2006 Wiley-Liss, Inc. [source]

Isolation and Characterization of Virgin Olive Oil Phenolic Compounds by HPLC/UV and GC-MS

JOURNAL OF FOOD SCIENCE, Issue 4 2001
M. Tasioula-margari
ABSTRACT This research examined the phenolic fraction of extra virgin olive oil samples from Lianolia variety olives grown in the region of Preveza, Greece. Phenolic compounds were extracted from oil samples, separated by reversed-phase high-performance liquid chromatography (HPLC), and characterized by gas chromatography-mass spectrometry (GC-MS). Both simple and complex phenols were detected with the latter being the most abundant. 3,4-Dihydroxyphenyl ethanol (hydroxytyrosol) and p-hydroxyphenylethanol (tyrosol) predominated among the simple phenols. Complex phenolic compounds were further separated by preparative HPLC and analyzed by GC-MS before and after hydrolysis. The presence of hydroxytyrosol and tyrosol derivatives was confirmed. Both derivatives were always present in greater quantities and made up an average exceeding 70% in all samples analyzed. [source]

Characterization of dihydrostreptomycin-related substances by liquid chromatography coupled to ion trap mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2009
Murali Pendela
Dihydrostreptomycin sulphate (DHS) is a water-soluble, broad-spectrum aminoglycoside antibiotic. For quantitative analysis, the European Pharmacopoeia (Ph. Eur.) prescribes an ion-pairing liquid chromatography/ultraviolet (LC/UV) method using a C18 stationary phase. Several unknown compounds were detected in commercial samples. Hence, for characterization of these unknown peaks in a commercial DHS sample, the Ph. Eur. method was coupled to mass spectrometry (MS). However, since the Ph. Eur. method uses a non-volatile mobile phase, each peak eluted was collected and desalted before introduction into the mass spectrometer. The desalting procedure was applied to remove the non volatile salt, buffer and ion-pairing reagent in the collected fraction. In total, 20 impurities were studied and 14 of them were newly characterized. Five impurities which are already reported in the literature were also traced in this LC/UV method. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Microbiological Benefits of Removing Foam Formed After UV-Enhanced Ozonation of Poultry-Processing Chiller Water for Recycling

JOURNAL OF FOOD SCIENCE, Issue 3 2002
M.E. Diaz
ABSTRACT: Prior experiments using 250 mL samples of unscreened poultry overflow chiller water evaluated the beneficial bactericidal and oxidative effects of 4 different treatments (namely, O2/O3,O2/UV, O2/O3/UV, and O2 as the control) for improving microbiological safety, turbidity, and water-use efficiency allowing its reconditioning for reuse. When excluding foam as in this present study, synergistic reductions > 1.5 log CFU/mL for aerobic plate counts (APC) were additionally achieved after 4 min for all O3/UV treatment combinations as compared to serially applied treatments of O3 and UV acting separately. With foam present, 16-min O3/UV treatments were required to achieve similar results. We now report these additional benefits achieved by removing the foam formed by the advanced oxidation process of ultraviolet-photon enhanced ozonation. Furthermore, foam microbial and general physical content were analyzed to determine suitability as an additive in rendering-type processes. Treatment of the wastewater resulted in total plate counts between 2 to 4 Log CFU/mL in the foam after 8 min. Fat and protein constituted 89% of the solids collected (384 mg/L or 14% of the foam) with trace amounts of metal elements (for example, Ca, Na, K, Fe, Cu) present. Irradiating had negligible effect on foam characteristics yet decreased the amount of solids collected. [source]

Advanced oxidation processes for destruction of cyanide from thermoelectric power station waste waters

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2004
José M Monteagudo
Abstract Several advanced oxidation processes for the destruction of cyanide contained in waste waters from thermoelectric power stations of combined-cycle were studied. Thus, oxidation processes involving ozonation at basic pH, ozone/hydrogen peroxide, ozone/ultraviolet radiation and ozone/hydrogen peroxide/ultraviolet radiation have been carried out in a semi-batch reactor. All these methods showed that total cyanide can be successfully degraded but with different reaction rates, and the decrease in the total cyanide concentration can be described by pseudo-first order kinetics. The influence of pH and initial concentration of hydrogen peroxide was studied to find the optimal conditions of the oxidation process. Experimental results of the single ozone treatment indicated that total cyanide is destroyed more rapidly at higher pH (12), while ozonation combined with H2O2 and/or UV is faster at pH 9.5. The optimum concentration of H2O2 was 20.58 × 10,2M because an excess of peroxide decreases the reaction rate, acting as a radical scavenger. The total cyanide degradation rate in the O3/H2O2(20.58 × 10,2M) treatment was the highest among all the combinations studied. However, COD reduction, in the processes using UV radiation such as O3/UV or O3/H2O2/UV was about 75%, while in the processes with H2O2 and/or O3/H2O2 was lower than 57% and was insignificant, when using ozone alone. Copyright © 2003 Society of Chemical Industry [source]

Removal of organic contaminants in paper pulp effluents by AOPs: an economic study

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2002
Montserrat Pérez
Abstract The degradation of the organic content of a bleaching Kraft mill effluent was carried out using Advanced Oxidation Processes (AOPs). The study was focused on the identification of the AOP, or combination of AOPs, that showed the highest efficiency together with the lowest cost. Direct UV photolysis (UV), TiO2 assisted-photocatalysis (TiO2/UV), Fenton, Fenton-like, and photo-Fenton reactions (Fe(II)/H2O/UV), UV-assisted ozonation (O3/UV) and addition of Fe2+ and/or H2O2 to the TiO2/UV and the O3/UV systems, were used for the degradation of a conventional cellulose bleaching effluent. The effluent was characterized by the general parameters TOC, COD and color, and analyzed for chlorinated low molecular weight compounds using GC,MS. The costs of the systems per unit of TOC reduction were compared. Fenton, Fenton-like and photo-Fenton reactions achieved better levels of TOC degradation than photocatalysis and with lower cost's than photocatalytic treatments. Ozonation is an effective but rather expensive process. The use of UVA light, however, increased the effectiveness of ozonation with a significant decrease (>25%) in the operational cost. © 2002 Society of Chemical Industry [source]

Decolorization of RR-120 Dye Using Ozone and Ozone/UV in a Semi-Batch Reactor

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2004
Mohammad Kazemi
Abstract Treatability of RR-120 aqueous dye solutions using O3 and O3/UV was studied in a bench scale set-up. Reduction in colour and chemical oxygen demand (COD) under various pH and initial dye concentrations were investigated. Pseudo first order reaction rate was satisfactorily used for kinetic interpretations in destruction of the dye. The results showed that decolorization with O3 was faster at neutral pH values. While use of UV had a small effect on ozonation at low pH values, UV radiation had a considerable effect at pH values of 7 and above. It was found that ozone utilization efficiency of higher than 95% could be attained in the experimental set up. On a étudié la possibilité de traitement de solutions aqueuses de colorant RR-120 à l'aide d'O3 et O3/UV dans un banc d'essai. La réduction de la demande chimique en oxygène (DCO) et en colorant a été étudiée pour différentes concentrations initiales de colorant. La vitesse de réaction du pseudo-premier ordre a été utilisée avec succès pour les interprétations cinétiques de la destruction du colorant. Les résultats montrent que la décoloration avec l'O3 est plus rapide à des valeurs de pH neutres. Alors que le recours aux UV a un faible effet sur l'ozonation à de faibles valeurs de pH, la radiation par UV a un effet considérable à des valeurs de pH de 7 et au-dessus. On a trouvé qu'une efficacité d'utilisation de l'ozone supérieure à 95% pouvait être atteinte dans l'installation expérimentale. [source]

Removal of organic contaminants in paper pulp effluents by AOPs: an economic study

Low temperature hydrothermal growth and optical properties of ZnO nanorods

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2009
J. H. Yang
Abstract Well-faceted hexagonal ZnO nanorods have been synthesized by a simple hydrothermal method at relative low temperature (90°C) without any catalysts or templates. Zinc oxide (ZnO) nanorods were grown in an aqueous solution that contained Zinc chloride (ZnCl2, Aldrich, purity 98%) and ammonia (25%). Most of the ZnO nanorods show the perfect hexagonal cross section and well-faceted top and side surfaces. The diameter of ZnO nanorods decreased with the reaction time prolonging. The samples have been characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) measurement. XRD pattern confirmed that the as-prepared ZnO was the single-phase wurtzite structure formation. SEM results showed that the samples were rod textures. The surface-related optical properties have been investigated by photoluminescence (PL) spectrum and Raman spectrum. Photoluminescence measurements showed each spectrum consists of a weak band ultraviolet (UV) band and a relatively broad visible light emission peak for the samples grown at different time. It has been found that the green emission in Raman measurement may be related to surface states. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Crystal growth, optical and luminescence properties of (Ce,Sr)-doped PrAlO3 single crystals

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2007
A. Novoselov
Abstract Using the micro-pulling-down method, (Ce,Sr)-doped PrAlO3 square-shaped single crystals (4×4×12 mm) were grown. Structural parameters studied by X-ray powder diffraction were consistent with R3m space group. Compositional homogeneity was checked with electron probe micro-analysis and found quite uniform. Absorption spectra and luminescence characteristics under UV and X-ray excitations were measured at room temperature with no Ce-related emission appeared. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Growth and characterisation of potassium cobalt nickel sulfate hexahydrate for UV light filters

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2006
Xinxin Zhuang
Abstract A new single crystal for ultraviolet light filter, KCNSH (Potassium Cobalt Nickel Sulfate Hexahydrate) was designed and its crystal structure was studied using X-ray diffraction in this paper. The empirical of the title compound is K2Co0.1Ni0.9(SO4)2.6H2O with formula weight 437.15. KCNSH crystal belongs to the monoclinic space group P2(1)/c, a=6.1390(3)Å, b=12.1839(6)Å, c=9.0095(4)Å, ,=,=90°, ,=105.060(2)°, V=650.74(5)Å3, Z=2, Dc=2.231g/cm3. Using the cooling solution method, we have grown a deep green KCNSH crystal with dimension of 12×12×40mm3. The transmission spectrum of KCNSH in the range from UV to near IR wavelengths, its thermal properties, and the relationship between the structure and optical transmission properties are also studied and further discussed in this paper. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Does Imiquimod Histologically Rejuvenate Ultraviolet Radiation,Damaged Skin?

DERMATOLOGIC SURGERY, Issue 12 2007
KATHLEEN SMITH MD
BACKGROUND Imiquimod (IMI) 5% is believed by some to result in an improved cosmetic appearance of chronically ultraviolet radiation (UV)-damaged skin. OBJECTIVE The objective was to determine what histologic and immunohistologic changes were present in actinically damaged skin after treatment with IMI. METHODS AND MATERIALS Pre- and posttherapy biopsies of 12 patients with histories of actinic keratoses were evaluated with routine histology and immunohistochemical stains including p53, p63, proliferating cell nuclear antigen (PCNA), c-kit, and Factor XIIIa. RESULTS After IMI therapy there was less compact hyperkeratosis, a more uniform rete ridge pattern with a more ordered proliferation of the epidermis, and a decrease in sun-damaged melanocytes. The papillary dermis showed a more uniform cellularity, and there was increased cellularity within the area of solar elastosis. After therapy, staining for p53, p63, and PCNA was decreased within the epidermis; staining for c-kit was decreased but more uniform in the basal cell; and Factor XIIIa expression was increased within the papillary dermis with a more ordered pattern of staining. CONCLUSION These morphologic and immunohistochemical patterns may explain some of the improvement in overall skin appearance after IMI therapy and may be related to the spectrum of signaling pathways induced by the imidazoquinolines. [source]

Effect of Laser Resurfacing on p53 Expression in Photoaged Facial Skin

DERMATOLOGIC SURGERY, Issue 6 2007
MOETAZ M. EL-DOMYATI MD
BACKGROUND p53 overexpression has been reported in photoaged skin. Meanwhile, p53 gene mutations have been implicated as an important factor in the pathogenesis of ultraviolet (UV) light,induced skin cancer. OBJECTIVE The objective was to evaluate the effect of laser resurfacing on the epidermal thickness and expression of p53 in photoaged skin. METHODS Specimens were obtained from the facial skin of 10 patients before and after 3 months and 1 year of treatment using CO2 (five cases) and erbium (Er):YAG (five cases) lasers. Specimens were also obtained from six age-matched controls. These biopsies were used for routine histopathology, histometry, and p53 immunoperoxidase staining. RESULTS Both CO2 and Er:YAG lasers were found to induce a significant decrease in p53 expression in biopsies obtained after 3 months (p=.0004 and .002, respectively) followed by gradual increase (p=.01 in both groups). A significant increase (p<.01) in epidermal thickness was also observed after 1 year of resurfacing. This increase, however, is inversely correlated with the level of p53 expression in such patients. CONCLUSION The decrease in epidermal p53 expression after CO2 and Er:YAG lasers may account for some of the benefits of resurfacing on the epidermis, as well as prevention of actinic neoplasia by adjusting any disturbance in the proliferation/apoptosis balance observed in photoaged facial skin. [source]

The Polyhydroxy Acid Gluconolactone Protects Against Ultraviolet Radiation in an In Vitro Model of Cutaneous Photoaging

DERMATOLOGIC SURGERY, Issue 2 2004
Eric F. Bernstein MD
Background. Ultraviolet (UV) radiation damages skin through a variety of mechanisms, including the generation of free radicals. Gluconolactone is a polyhydroxy acid (PHA) that is capable of chelating metals and may also function by scavenging free radicals, thereby protecting skin from some of the damaging effects of UV radiation. Objective. This study measured the ability of gluconolactone to protect against UV radiation,induced damage. Methods. The ability of gluconolactone to prevent UV radiation,induced elastin promoter activation was determined in vitro using a transgenic model of cutaneous photoaging. Gluconolactone was also evaluated to determine its ability to promote the formation of sunburn cells in human skin after exposure to UV radiation. Results. Gluconolactone provided up to 50% protection against UV radiation, as measured in our in vitro system, and did not significantly increase sunburn cells in human skin. Conclusions. These results demonstrate the ability of the PHA gluconolactone to protect against UV radiation,induced elastin promoter activation. In addition, in vivo studies demonstrated that gluconolactone treatment does not result in a significant increase in sunburn cells. Further investigation of this and other PHAs is necessary to identify their potential role in preventing and repairing cutaneous photodamage. [source]

Interaction of vitamins C and E as better cosmeceuticals

DERMATOLOGIC THERAPY, Issue 5 2007
Karen E Burke
ABSTRACT:, Although many cosmeceutical formulations contain vitamin C and/or vitamin E, very few are actually effective in topical application. First because there is only a low concentration, second because the stability is compromised as soon as the product is opened and exposed to air and light, and third because the form of the molecule (an ester or a mixture of isomers) is not absorbed or metabolized effectively by the skin. However, when a stable formulation delivers a high concentration of the nonesterified, optimal isomer of the antioxidant, vitamins C and E do indeed inhibit the acute ultraviolet (UV) damage of erythema, sunburn, and tanning as well as chronic UV photoaging and skin cancer. Both are highly effective depigmenting agents. Topical vitamin C also increases collagen synthesis in both young and old fibroblasts. Because vitamin C regenerates oxidized vitamin E, the combination in a cosmeceutical formulation is synergistic , particularly in UV protection. [source]

Topical and systemic photoprotection

DERMATOLOGIC THERAPY, Issue 1 2003
Cheryl F. Rosen
ABSTRACT: Sunscreens are a valuable method of sun protection. Several new compounds are now available. It is important to remember, however, that photoprotection includes more than the use of sunscreens. There are a number of sun-protective behaviors that people can use to decrease their exposure to ultraviolet (UV) radiation. Dermatologists and other health professionals can work toward changing public policy, greatly increasing the ability of people to access shade. In addition, there is growing evidence about the effectiveness of other sun-protective agents. The only systemic medication for sun protection is ,-carotene, which is effective in erythropoietic protoporphyria (EPP). [source]

Influence of ambient light on the evolution of colour signals: comparative analysis of a Neotropical rainforest bird community

ECOLOGY LETTERS, Issue 4 2004
Doris Gomez
Abstract Rainforests offer two contrasted light environments: a bright canopy rich in blue and UV and a dark understorey, rich in green and orange. Therefore, natural selection for crypsis should favour dark brown signals in understorey and bright green signals in canopy, whereas sexual selection for conspicuousness should favour bright yellow-red signals in understorey and dark blue and UV signals in canopy. Using spectrometry and comparative analyses, we examined the relationship between ambient light and colour signals in a bird community of French Guiana. It appears that brightness and hue are mostly naturally selected, while UV content of plumage is more likely sexually selected. At each height, both sexes present similar coloration but males display more conspicuous sexually selected patterns than females. These results show that ambient light drives the evolution of colour signals at community scale, and should be considered when studying signalling in other communities and light-contrasted ecosystems. [source]

Preparation of Novel Arrays Silver Nanoparticles Modified Polyrutin Coat-Paraffin-Impregnated Graphite Electrode for Tyrosine and Tryptophan's Oxidation

ELECTROANALYSIS, Issue 8 2008
Guan-Ping Jin
Abstract A novel array silver nanoparticles and Rutin complex film modified paraffin-impregnated graphite electrode was proposed in this work (denoted as Ag/Rutin/WGE). The characteristics were investigated by the field emission scanning electron microscopy (FE-SEM), infrared spectra (IR), UV-visible (UV), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. Silver ions were gradually chelated by polyrutin film at 4,-oxo-5,-OH and 5-OH-4-oxo sites accompanying adsorption, then. Silver nanoparticles were highly-dispersed electrodeposited on polyrutin film. The electrochemical behaviors of tyrosine (Tyr) and tryptophan (Trp) were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The Ag/Rutin/WGE electrode shows overlapping catalysis for the oxidation of Tyr and Trp. The linear response of Tyr and Trp were 0.3,10.0 and 0.7,70.0,,M with detection limit of 0.07 and 0.1,,M in a signal-to-noise ratio of 3. [source]

Development of 230,270 nm AlGaN-based deep-UV LEDs

ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 3 2010
Hideki Hirayama
Abstract We demonstrated AlGaN multi-quantum well (MQW) deep-ultraviolet (UV) light-emitting diodes (LEDs) with wavelengths in the range of 227.5 to 273 nm fabricated on high-quality AlN buffers on sapphire substrates grown by metal-organic chemical vapor deposition (MOCVD). We realized crack-free, thick AlN buffers on sapphire with a low threading dislocation density (TDD) and an atomically flat surface by using the ammonia (NH3) pulse-flow multilayer (ML) growth technique. We obtained single-peaked operation of an AlGaN-MQW LED with a wavelength of 227.5 nm, which is the shortest wavelength of AlGaN-based LED on sapphire. The maximum output power and the external quantum efficiency (EQE) of the 261- and 227.5-nm LEDs were 1.65 mW and 0.23% in room-temperature (RT) continuous-wave (CW) operation, and 0.15 mW and 0.2% in RT pulsed operation, respectively. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(3): 24,33, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10197 [source]

Analysis of amphetamine-type substances by capillary zone electrophoresis using capacitively coupled contactless conductivity detection

ELECTROPHORESIS, Issue 15 2010
Rochelle Epple
Abstract CE with capacitively coupled contactless conductivity detection (C4D) was employed for the separation and detection of seven amphetamine analogues as well as amphetamine, dextroamphetamine, methamphetamine and 3,4-methylenedioxymethamphetamine. The separation electrolyte was 30,mM hydroxypropyl-,-cyclodextrin (HP,CD) in a 75,mM acetic acid+25,mM sodium acetate buffer adjusted to pH 4.55. Conductivity detection was compared with UV detection using this same electrolyte. Average detection limits for C4D and UV were 1.3 and 1.0,ppm, respectively. The effects of HP,CD concentration and BGE composition on the selectivity of the separation were also investigated. An illicit, street-grade sample of 3,4-methylenedioxymethamphetamine (Ecstasy) and a prescription dextroamphetamine tablet were also analysed. [source]

Cyclodextrin-based nonaqueous electrokinetic chromatography with UV and mass spectrometric detection: Application to the impurity profiling of amiodarone,

ELECTROPHORESIS, Issue 17 2008
Roelof Mol
Abstract The potential of nonaqueous electrokinetic chromatography (NAEKC) using cyclodextrins (CD) for the analysis of basic drugs and related compounds was evaluated. Both UV absorbance and mass spectrometric (MS) detection were employed. Addition of neutral CD to the NA background electrolyte did not significantly enhance the separation of a test mixture of basic drugs, and no change in selectivity was observed. In contrast, anionic single-isomer-sulfated CD strongly added to the selectivity of the NAEKC system inducing an improved resolution among the test compounds and increasing the migration time window. The applicability of the NAEKC system using anionic CD is demonstrated by the profiling of a sample of the drug amiodarone that had been stored for 1,year at room temperature. Amiodarone is poorly soluble in water. NAEKC-UV analysis indicated the presence of at least seven impurities in the amiodarone sample. In order to identify these compounds, the NAEKC system was coupled directly to electrospray ionization (ESI) ion-trap MS. The total of detected impurities increased to 12 due to the added sensitivity and selectivity of MS detection. Based on the acquired MS/MS data, three sample constituents could be identified as ,known' impurities (British Pharmacopoeia), whereas for three unknown impurities molecular structures could be proposed. Estimated limits of detection for amiodarone using the NAEKC method were 1,,g/mL with UV detection and 15,ng/mL with ESI-MS detection (full-scan). Based on relative responses, the impurity content of the stored drug substance was estimated to be 0.33 and 0.47% using NAEKC-UV and NAEKC-ESI-MS, respectively. [source]

Open-tubular capillary electrochromatography using a capillary coated with octadecylamine-capped gold nanoparticles

ELECTROPHORESIS, Issue 4 2008
Qishu Qu Dr.
Abstract Octadecylamine-capped gold nanoparticles (ODA-Au-NPs) were prepared and characterized by using UV,Vis adsorption spectrum, transmission electron chromatography (TEM), SEM, and FT-IR. A simple but robust hydrophobic coating was easily developed by flushing a capillary with a solution of ODA-Au-NPs, because the positive charges were carried by the nanoparticles which strongly adsorb to the negatively charged inner surface of a fused-silica capillary via electrostatic and hydrophobic interactions. The chromatographic characteristics of the coated capillary was investigated by varying the experimental parameters such as buffer pH, buffer concentration, and percentage of organic modifier in the mobile phase. The results show that (i) resolution between thiourea and naphthalene is almost the same when comparing the electrochromatograms obtained using pH,7 buffer as mobile phase after and before the capillary column was operated using pH,11 and 3 mobile phase; (ii) no significant changes in retention time and deterioration in peak efficiency were found after 60,runs of test aromatic mixtures; and (iii) column efficiency up to 189,000 theoretical plates/meter for testosterone was obtained. All of the results indicated that the coating could act as a stable stationary phase for open tubular CEC as well as for bioanalysis. [source]

Analyses of alkaloids in different products by NACE-MS

ELECTROPHORESIS, Issue 22 2007
Chen-Wen Chiu
Abstract A simple method for the separation and characterization of five nicotine-related alkaloids by NACE employing UV and MS detections is described here for the first time. Several factors, including NACE parameters (compositions of running solution) and MS parameters (such as nature and flow rate of sheath liquid, pressure of nebulization gas, and flow rate of dry gas), were optimized in order to obtain both an adequate CE separation and high MS signals for the alkaloid compounds used in this study. A reliable CE separation of five alkaloids was achieved in 50,mM ammonium formate that was dissolved in an ACN/methanol mixture (50:50, v/v) of pH*,4.0 (apparent pH 4.0). The optimal electrospray MS measurement was carried out in the positive ionization mode using a coaxial sheath liquid composed of isopropyl alcohol and water in the ratio of 80:20 v/v at a flow rate of 180,,L/h. In addition, the proposed NACE method was also applied in the analyses of alkaloids in several products including chewing gums, beverages, and tobaccos. This NACE-MS method was found to provide a better detection ability and separation resolution for the analysis of nicotine alkaloids when compared to other aqueous CE-MS reports. [source]

Light-emitting diode-compatible probes for indirect detection of anions in CE

ELECTROPHORESIS, Issue 19 2007
Peter Balding
Abstract A range of compounds were evaluated as probes for the indirect detection of inorganic ions using CE and light-emitting diodes (LEDs) as the light source. Emphasis was placed on examining probes likely to absorb strongly in the UV,Vis region near 350,430,nm as compounds, which absorb at longer wavelengths tend to be bulkier and adsorb onto the capillary wall. These probes should act as a replacement for the very effective but carcinogenic probe chromate. Two probes were identified and evaluated: p -nitrophenol and 4-hydroxy-3,5-dinitrobenzoic acid. The former showed the most potential with low-mobility anions, while the later had a moderate electrophoretic mobility and was more suitable for a wider mobility range of analytes. However, neither could match the efficiencies and LOD of chromate for the separation of the fast inorganic ions such as chloride, nitrate and sulphate. Nevertheless, application of the 4-hydroxy-3,5-dinitrobenzoic acid system to the determination of oxalate in Bayer liquors showed excellent sensitivity and selectivity. [source]

Simultaneous determination of low-molecular-weight organic acids and chlorinated acid herbicides in environmental water by a portable CE system with contactless conductivity detection

ELECTROPHORESIS, Issue 10 2007
Yan Xu
Abstract This report describes a method to simultaneously determine 11 low-molecular-weight (LMW) organic acids and 16 chlorinated acid herbicides within a single run by a portable CE system with contactless conductivity detection (CCD) in a poly(vinyl alcohol) (PVA)-coated capillary. Under the optimized condition, the LODs of CE-CCD ranged from 0.056 to 0.270,ppm, which were better than for indirect UV (IUV) detection of the 11 LMW organic acids or UV detection of the 16 chlorinated acid herbicides. Combined with an on-line field-amplified sample stacking (FASS) procedure, sensitivity enhancement of 632- to 1078-fold was achieved, with satisfactory reproducibility (RSDs of migration times less than 2.2%, and RSDs of peak areas less than 5.1%). The FASS-CE-CCD method was successfully applied to determine the two groups of acidic pollutants in two kinds of environmental water samples. The portable CE-CCD system shows advantages such as simplicity, cost effectiveness, and miniaturization. Therefore, the method presented in this report has great potential for onsite analysis of various pollutants at the trace level. [source]

Data processing in metabolic fingerprinting by CE-UV: Application to urine samples from autistic children

ELECTROPHORESIS, Issue 6 2007
Ana C. Soria
Abstract Metabolic fingerprinting of biofluids such as urine can be used to detect and analyse differences between individuals. However, before pattern recognition methods can be utilised for classification, preprocessing techniques for the denoising, baseline removal, normalisation and alignment of electropherograms must be applied. Here a MEKC method using diode array detection has been used for high-resolution separation of both charged and neutral metabolites. Novel and generic algorithms have been developed for use prior to multivariate data analysis. Alignment is achieved by combining the use of reference peaks with a method that uses information from multiple wavelengths to align electropherograms to a reference signal. This metabolic fingerprinting approach by MEKC has been applied for the first time to urine samples from autistic and control children in a nontargeted and unbiased search for markers for autism. Although no biomarkers for autism could be determined using MEKC data here, the general approach presented could also be applied to the processing of other data collected by CE with UV,Vis detection. [source]