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Diode Array (diode + array)
Terms modified by Diode Array Selected AbstractsFabrication of Large-Area Silicon Nanowire p,n Junction Diode Arrays,ADVANCED MATERIALS, Issue 1 2004K. Q. Peng Large-area silicon nanowire p,n junction diode arrays (see Figure) have been fabricated by chemical etching of planar silicon p,n junction wafers in aqueous HF solution that contains appropriate amounts of silver nitrate near room temperature. The I,V characteristics have been measured using current-sensing atomic force microscopy, and nonlinear and rectifying electrical transport behavior has been observed. [source] Extraction, Identification, and Quantification of Flavonoids and Phenolic Acids in Electron Beam-Irradiated Almond Skin PowderJOURNAL OF FOOD SCIENCE, Issue 3 2009A.S. Teets ABSTRACT:, The effect of electron beam irradiation doses from 0 to 30 kGy on extraction yield and phenolic compounds was evaluated in almond skin phenolic extracts (ASPE). Total soluble phenols and distribution of phenolic compounds from acidified methanol ASPE and 52% methanol ASPE were quantified using Folin,Ciocalteau method, liquid chromatography with diode array and fluorescence detection, and negative ion electrospray-mass spectrometry. Electron beam irradiation increased extraction yield by as much as 23%, with the greatest increase observed in the acidified methanol ASPE. Irradiated samples extracted with acidified methanol also exhibited an increase in extractable phenols (Folin,Ciocalteau) and total HPLC-resolved phenolics at all irradiation doses. Samples extracted with 52% methanol exhibited an increase at 10 and 20 kGy, but a 31% decrease at 30 kGy. An increase in aglycones respective to their glycosides was not observed with irradiation. Therefore, the increase in phenolics was attributed to release of phenolics from their cellular matrix. [source] Multi-residue method for the analysis of pharmaceutical compounds in sewage sludge, compost and sediments by sonication-assisted extraction and LC determinationJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2010Julia Martín Abstract A method for the simultaneous determination of 16 pharmaceutical compounds in three types of sewage sludge (primary, secondary and anaerobically digested dehydrated sludge), compost and sediment samples is described. Pharmaceutical compounds evaluated were nonsteroidal anti-inflammatory drugs (acetaminophen, diclofenac, ibuprofen, ketoprofen, naproxen and salicylic acid), antibiotics (sulfamethoxazole and trimethoprim), an anti-epileptic drug (carbamazepine), a ,-blocker (propranolol), a nervous stimulant (caffeine), estrogens (17,-ethinylestradiol, 17,-estradiol, estriol and estrone) and lipid regulators (clofibric acid, metabolite of clofibrate and gemfibrozil). The method is based on the ultrasonic-assisted extraction, clean-up by SPE and analytical determination by HPLC with diode array and fluorescence detectors. The best extraction recoveries were achieved in a three-step extraction procedure with methanol and acetone as extraction solvents. Extraction recoveries of several pharmaceutical compounds as caffeine were highly dependent on the type of sample evaluated. The applicability of the method was tested by analyzing primary, secondary and anaerobically digested dehydrated sludge, compost and sediment samples from Seville (Southern Spain). Ten of the sixteen pharmaceutical compounds were detected in sludge samples and five in compost and sediment samples. The highest concentration levels were recorded for ibuprofen in sewage samples, whereas salicylic acid and 17,-ethinylestradiol were detected in all of the samples analyzed. [source] Visible light initiated polymerization of styrenic monolithic stationary phases using 470,nm light emitting diode arraysJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2010Zarah Walsh Abstract Poly(styrene- co -divinylbenzene) monolithic stationary phases have been synthesized for the first time by photoinitiated polymerization. An initiator composed of (+)-(S)-camphorquinone/ethyl-4-dimethylaminobenzoate/N- methoxy-4-phenylpyridinium tetrafluoroborate was activated using a 470,nm light emitting diode array as the light source. Spatially controlled polymerization of styrenic monoliths has been achieved within specific sections of a 100,,m id polytetrafluoroethylene-coated fused-silica capillary using simple photo masking. The sharpness of the edges was confirmed by optical microscopy, while SEM was used to verify a typical porous, globular morphology. Flow resistance data were used to assess the permeability of the monoliths and they were found to have good flow through properties with a flow resistance of 0.725,MPa/cm at 1,,L/min (water, 20°C). Conductivity profiling along the length of the capillary was used to assess their lateral homogeneity. Monoliths which were axially rotated during polymerization were found to be homogeneous along the whole length of the capillary. The monolithic stationary phases were applied to the RP gradient separation of a mixture of proteins. Column fabrication showed excellent reproducibility with the retention factor (k) having a RSD value of 2.6% for the batch and less than 1.73% on individual columns. [source] Determination of seventeen main flavonoids and saponins in the medicinal plant Huang-qi (Radix Astragali) by HPLC-DAD-ELSDJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2007Qing-Tao Yu Abstract A simple, rapid, and reliable method, namely high-performance liquid chromatography coupled with diode array and evaporative light scattering detectors (HPLC-DAD-ELSD), was developed to simultaneously determine twelve major flavonoids and five main saponins in different parts of the medicinal plant Huang-qi (Radix Astragali). The DAD wavelength was set at 280 nm for the UV detection of flavonoids, while the drift tube temperature was set at 105°C and the nebulizing gas flow rate at 2.7 L/min for ELSD detection of saponins. The method was fully validated with respect to linearity (r2 >0.998), sensitivity, precision, and accuracy (recovery rate between 93.3 and 104.2%). The analytical results of different parts of the medicinal plant Huang-qi revealed that the levels of total flavonoids or saponins in individual parts can vary considerably and the concentration of each compound in different parts is also significantly different. The aerial parts (stems and leaves) contain even higher total contents of flavonoids (although of different kinds) than the commonly used roots of the plants. In addition, the concentration of total flavonoids and saponins in the extract of the fibrous roots was surprisingly highest among all parts of Astragalus species. All of these findings provide clear evidence and scientific support for utilization of different parts of the medicinal plant Huang-qi and also for reduction in waste of plant resources. [source] Simultaneous determination of carotenoids, tocopherols, and ,-oryzanol in crude rice bran oil by liquid chromatography coupled to diode array and mass spectrometric detection employing silica C30 stationary phasesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2005Wolfgang Stöggl Abstract Crude rice bran oil contains tocopherols (vitamin E), carotenoids (vitamin A), and phytosterols, which possess antioxidant activities and show promising effects as preventive and therapeutic agents. The aim of this work was to establish methods and to compare C18 and C30 silica stationary phases in order to separate and detect tocopherols, carotenoids, and ,-oryzanol in one single run. Comparing RP-LC on silica C18 and C30, higher resolution between all target compounds was obtained using the C30 stationary phase. Methanol was used as eluent and the elution strength was increased by the addition of tert -butyl methyl ether for highly hydrophobic analytes such as ,-oryzanol. Detection was accomplished by diode array detection from 200 to 500 nm. Absorbance maxima were found at 295 nm for tocopherols, 324 nm for ,-oryzanol, and 450 nm for carotenoids. Furthermore, compounds were characterized and identified on the basis of their UV-spectra. Both RP systems were coupled to MS (LC-MS) by using an atmospheric pressure chemical ionization interface. [source] Design of a vacuum-compatible high-precision monochromatic beam-position monitor for use with synchrotron radiation from 5 to 25,keVJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2000R. W. Alkire The Structural Biology Center beamline, 19ID, has been designed to take full advantage of the highly intense undulator radiation and very low source emittance available at the Advanced Photon Source. In order to keep the X-ray beam focused onto the pre-sample slits, a novel position-sensitive PIN diode array has been developed. The array consists of four PIN diodes positioned upstream of a 0.5,µm-thick metal foil placed in the X-ray beam. Using conventional difference-over-the-sum techniques, two-dimensional position information is obtained from the metal foil fluorescence. Because the full X-ray beam passes through the metal foil, the true beam center-of-mass is measured. The device is compact, inexpensive to construct, operates in a vacuum and has a working range of 8,mm × 10,mm that can be expanded with design modifications. Measured position sensitivity is 1,2,µm. Although optimized for use in the 5,25,keV energy range, the upper limit can be extended by changing metals or adjusting foil thickness. [source] High-performance liquid chromatography with diode array detection coupled to electrospray time-of-flight and ion-trap tandem mass spectrometry to identify phenolic compounds from a Cistus ladanifer aqueous extractPHYTOCHEMICAL ANALYSIS, Issue 4 2010S. Fernández-Arroyo Abstract Introduction , Cistus ladanifer is an aromatic shrub that is widespread in the Mediterranean region. The labdanum exudate is used in the fragrance industry and has been characterised. However, there is not enough information about the phenolic content of the raw plant, the aerial part of it being a very rich source of bioactive compounds. Objective , Characterisation of the bioactive compounds of the raw plant and its aerial parts. Methodology , High-performance liquid chromatography with diode array and electrospray ionisation mass spectrometric detection was used to carry out the comprehensive characterisation of a Cistus ladanifer shrub aqueous extract. Two different MS techniques were coupled to HPLC: time-of-flight mass spectrometry and tandem mass spectrometry. Results , Many well-known compounds present in Cistus ladanifer were characterised, such as flavonoids, phenolic acids, ellagitanins, hexahydroxydiphenoyl and derivatives, and other compounds. Conclusion , The method described simultaneously separated a wide range of phenolic compounds and the proposed characterisation of the major compounds of this extract was carried out. It is important to highlight that, to our knowledge, this is the first time that a Cistus ladanifer aqueous extract from the raw plant has been characterised. Copyright © 2009 John Wiley & Sons, Ltd. [source] Simultaneous determination of twelve bioactive constituents in Buyang Huanwu decoction by HPLC-DAD-ELSD and HPLC-TOF/MSBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010E-Hu Liu Abstract Buyang Huanwu Decoction (BYHYD) is a classical traditional Chinese medicinal prescription that has been widely used for treating cerebrovascular illnesses for hundreds of years. In this study, a comprehensive analytical method has been developed for quantitative analysis of the major constituents in BYHWD. This method was based on high-performance liquid chromatography coupled to a diode array and evaporative light scattering detectors (HPLC-DAD-ELSD) on a common reverse-phase C18 column. HPLC coupled with on-line time-of-flight mass spectrometry (HPLC-TOF/MS) was additionally adopted to provide further validation for the constituents. It was found that 0.3% aqueous formic acid and acetonitrile was the optimum mobile phase for gradient elution. This method, which showed excellent precision and accuracy, was successfully applied to quantify the bioactive constituents in six BYHWD products. The validated HPLC-DAD-ELSD method, together with the HPLC-TOF/MS analysis, provided a new basis for assessing the quality of traditional Chinese medicinal prescription consisting of many bioactive components. Copyright © 2009 John Wiley & Sons, Ltd. [source] Evaluation of GSH adducts of adrenaline in biological samplesBIOMEDICAL CHROMATOGRAPHY, Issue 7 2007Renata Silva Abstract The sustained high release of catecholamines to circulation is a deleterious condition that may induce toxicity, which seems to be partially related to the products formed by oxidation of catecholamines that can be further conjugated with glutathione (GSH). The aim of the present study was to develop a method for the determination of GSH adducts of adrenaline in biological samples. Two position isomers of the glutathion-S-yl-adrenaline were synthesized and characterized by HPLC using diode array, coulometric and mass detectors. A method for the extraction of these adducts from human plasma was also developed, based on adsorption to activated alumina, which showed adequate recoveries and proved to be crucial in removing interferences from plasma. The selectivity, precision and linearity of the method were all within the accepted values for these parameters. Furthermore, the sensitivity of this method allows the detection of adduct amounts that are within the range of the expected concentrations for these adducts under certain pathophysiological conditions and/or drug treatments. In conclusion, the development of this method allows the direct analysis of GSH adducts of adrenaline in human plasma, providing a valuable tool for the study of the catecholamine oxidation process and its related toxicity. Copyright © 2007 John Wiley & Sons, Ltd. [source] Fabrication of Large-Area Silicon Nanowire p,n Junction Diode Arrays,ADVANCED MATERIALS, Issue 1 2004K. Q. Peng Large-area silicon nanowire p,n junction diode arrays (see Figure) have been fabricated by chemical etching of planar silicon p,n junction wafers in aqueous HF solution that contains appropriate amounts of silver nitrate near room temperature. The I,V characteristics have been measured using current-sensing atomic force microscopy, and nonlinear and rectifying electrical transport behavior has been observed. [source] Visible light initiated polymerization of styrenic monolithic stationary phases using 470,nm light emitting diode arraysJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2010Zarah Walsh Abstract Poly(styrene- co -divinylbenzene) monolithic stationary phases have been synthesized for the first time by photoinitiated polymerization. An initiator composed of (+)-(S)-camphorquinone/ethyl-4-dimethylaminobenzoate/N- methoxy-4-phenylpyridinium tetrafluoroborate was activated using a 470,nm light emitting diode array as the light source. Spatially controlled polymerization of styrenic monoliths has been achieved within specific sections of a 100,,m id polytetrafluoroethylene-coated fused-silica capillary using simple photo masking. The sharpness of the edges was confirmed by optical microscopy, while SEM was used to verify a typical porous, globular morphology. Flow resistance data were used to assess the permeability of the monoliths and they were found to have good flow through properties with a flow resistance of 0.725,MPa/cm at 1,,L/min (water, 20°C). Conductivity profiling along the length of the capillary was used to assess their lateral homogeneity. Monoliths which were axially rotated during polymerization were found to be homogeneous along the whole length of the capillary. The monolithic stationary phases were applied to the RP gradient separation of a mixture of proteins. Column fabrication showed excellent reproducibility with the retention factor (k) having a RSD value of 2.6% for the batch and less than 1.73% on individual columns. [source] Electro-optic Q-switched Yb:YAG slab laserLASER PHYSICS LETTERS, Issue 5 2006Q. Liu Abstract A novel side-pumped structure with microlens-free diode arrays and a lensduct was demonstrated. This structure is much more robust and simple than traditional approach of a microlens-conditioned diode arrays with a lensduct. A quasi-CW diode arrays side-pumped KD*P Q-switched Yb:YAG slab laser has been demonstrated. An output energy of ,10 mJ/pulse with pulse width as short as ,20ns is obtained at 1,10 Hz repetition rate. To our knowledge, this is the shortest pulse width of Electro-optic Q-switched laser output by using Yb:YAG as the gain medium. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] | ||||||||||