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Photodiode Array Detection (photodiode + array_detection)
Selected AbstractsA survey of sesamin and composition of tocopherol variability from seeds of eleven diverse sesame (Sesamum indicum L.) genotypes using HPLC-PAD-ECDPHYTOCHEMICAL ANALYSIS, Issue 4 2008Kelly S. Williamson Abstract The objective of this study was to determine the composition and content of sesamin and desmethyl tocopherols such as , -tocopherol (,T), , -tocopherol (,T) and , -tocopherol (,T) in seeds of sesame (Sesamum indicum L.) for 11 genotypes conserved in the United States Department of Agriculture (USDA), Agricultural Research Service (ARS) and Plant Genetic Resources Conservation Unit (PGRCU) in Griffin, Georgia, USA. Seed accessions studied were collections from eight countries worldwide, including one landrace from Thailand and two cultivars from Texas, USA. Novel methodologies and analytical techniques described herein consisted of reverse-phase high-performance liquid chromatography (HPLC) connected in series with two detection systems specific for each analyte class. Photodiode array detection was employed for sesamin analysis and electrochemical array detection was used in the determination of tocopherols. A preliminary study was conducted to assess sesamin levels in 2003 and tocopherol levels in 2004 from sesame seed samples conserved at the USDA, ARS and PGRCU. In 2005, sesame seed samples were grown, harvested and evaluated for sesamin as well as tocopherol levels. The overall results (n = 3) showed that sesamin, ,T, ,T and ,T levels were 0.67,6.35 mg/g, 0.034,0.175 µg/g, 0.44,3.05 µg/g and 56.9,99.3 µg/g respectively, indicating that the sesame seed accessions contained higher levels of sesamin and ,T compared with ,T and ,T. Statistical analysis was conducted and significant differences were observed among the 11 different sesame genotypes. This suggests that genetic, environmental and geographical factors influence sesamin and desmethyl tocopherol content. Copyright © 2007 John Wiley & Sons, Ltd. [source] Determination of uranium, iron, copper, and nickel from ore samples by MEKC using N,N,-ethylene bis(salicylaldimine) as complexing reagentELECTROPHORESIS, Issue 3 2008Muhammed Aslam Mirza Abstract An analytical procedure has been developed for the separation of dioxouranium(VI), iron(III), copper(II), nickel(II), cobalt(II), cobalt(III), palladium(II), and thorium(IV) by MEKC using N,N,-ethylene bis(salicylaldimine) (H2SA2en) as a complexing reagent with total runtime <4.5,min. SDS was used as micellar medium at pH,8 with sodium tetraborate buffer (0.1,M). An uncoated fused-silica capillary with an effective length of 50,cm×75,,m id was used with an applied voltage of 30,kV with photodiode array detection at 231,nm. Linear calibrations were obtained within 0.111,1000,,g/mL of each element with LODs within 37,325,ng/mL. The developed method was tested for analysis of uranium ore samples indicating its presence within 103,1789,,g/g with RSD within 0.79,1.87%. Likewise copper, nickel, and iron in their combined matrix were also simultaneously determined with RSD 0.4,1.6% (n,=,6). [source] Determination of glyoxal and methylglyoxal in the serum of diabetic patients by MEKC using stilbenediamine as derivatizing reagentELECTROPHORESIS, Issue 21 2007Muhammad A. Mirza Abstract An analytical method has been developed for the separation of glyoxal (Go), methylglyoxal (MGo), and dimethylglyoxal (DMGo) by MEKC using stilbenediamine (SD) as derivatizing reagent, separation time 6.5,min, SDS as micellar medium at pH,8, and sodium tetraborate (0.1,M) as buffer. Uncoated fused-silica capillary, effective length 50,cm×75,,m id; applied voltage 20,kV and photodiode array detection, were used. Calibration was linear within 0.02,150,,g/mL with detection limits 3.5,5.8,ng/mL. Go and MGo, observed for diabetic and healthy volunteers, were within 0.098,0.193,,g/mL Go and 0.106,0.245,,g/mL MGo with RSD 1.6,3.5 and 1.7,3.4%, respectively, in diabetics against 0.016,0.046,,g/mL Go and 0.021,0.066,,g/mL MGo with RSDs 1.5,3.5 and 1.4,3.6%, respectively, in healthy volunteers. Go and MGo in diabetics were also measured by standard addition and DMGo as an internal standard. Additives do not contribute significantly to Go and MGo matrix. [source] Toxicology of a Microcystis ichthyoblabe waterbloom from Lake Oued Mellah (Morocco)ENVIRONMENTAL TOXICOLOGY, Issue 1 2002Brahim Sabour Abstract In the Lake Oued Mellah cyanobacteria waterblooms occur periodically in late spring and summer with Microcystis ichthyoblabe as the main bloom-forming species. In 1999, a heavy waterbloom of M. ichthyoblabe occurred during May June with a maximal biomass of 298 mg/l. During this period, several bloom samples were collected. The toxicity assessment was done by mouse and brine shrimp (Artemia) bioassays. Apart from the sample collected on 15/06/1999, all the other samples were toxic by mouse bioassay. The LD50 determined by intraperitoneal injection to mice during active cyanobacterial growth and decline phases were 518 and 1924 mgDW/kg respectively. Using Artemia bioassay, the 24hLC50 varied from 6.0 to 40.6 mg/ml and the 48hLC50 ranged from 2.8 to 18.2 mg/ml. The separation and identification of microcystin variants was performed by high performance liquid chromatography,photodiode array detection. Eleven toxins were separated and preliminarily identified as microcystin variants as they exhibit a typical UV spectra like the microcystin-LR standard. The quantification of total microcystins determined by enzyme-linked immunosorbent assay showed that the contents were varied between 0.1 and 0.76 ,g/g DW. © 2002 by Wiley Periodicals, Inc. Environ Toxicol 17: 24,31, 2002 [source] Detection and quantification of microcystins from cyanobacteria strains isolated from reservoirs and ponds in MoroccoENVIRONMENTAL TOXICOLOGY, Issue 1 2002B. Oudra Abstract In Morocco, the occurrence of toxic cyanobacteria blooms is confirmed in some water bodies used for recreational and/or as drinking water reservoirs. According to WHO recommendations, the establishment of a monitoring program for microcystins is a necessity. This paper presents toxicological studies of 19 toxic cyanobacteria strains of Microcystis, Synechocystis, Pseudanabaena, and Oscillatoria. These strains were isolated from various water bodies including natural lakes, reservoirs, and ponds located in central regions of Morocco. The isolation, culture, and biomass production of these strains was made on Z8 or BG13 media under laboratory controlled conditions. The hepatotoxicity of cyanobacterial lyophilized material was confirmed by mouse bioassays. The amount of microcystins produced by each strain was determined by the enzyme-linked immunosorbent assay (ELISA). The detection and identification of microcystin variants was performed by high performance liquid chromatography (HPLC) with photodiode array detection. Almost all strains showed medium to high toxicity, the estimated LD50 i.p mice bioassay ranged between 28 to 350 mg/kg body weight. The concentrations of microcystins varied between 2.16 to 944 ,g/g and 26.8 to 1884 ,g/g dry weight determined by ELISA and HPLC, respectively. The screening of bloom-forming and microcystin producer cyanobacteria strains in these fresh water bodies leads us to propose the need for the establishment of a survey of cyanobacteria and a cyanotoxin-monitoring program. © 2002 by Wiley Periodicals, Inc. Environ Toxicol 17: 32,39, 2002 [source] Fast CE analysis of adrenergic amines in different parts of Citrus aurantium fruit and dietary supplementsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 16 2010Laura Mercolini Abstract A CE method has been developed for the simultaneous analysis of the adrenergic amines synephrine, octopamine and tyramine in Citrus aurantium (bitter orange) fruit extracts and in dietary supplements. The analytes were separated on a fused silica capillary (50,,m id, 40.0,cm effective length, 48.5,cm total length) using a BGE composed of phosphate buffer (pH 2.5, 50,mM) and applying a 30,kV potential. The samples were injected hydrodynamically at 50,mbar for 25,s. The use of photodiode array detection (,=195,nm) allowed the quantification of the analytes and the control of peak purity. The method has been fully validated, obtaining satisfactory values of precision and extraction yield. The analytes are extracted with water from the dried whole fruits or fruit parts (endocarp, mesocarp and exocarp) or from the commercial formulations and directly injected into the CE apparatus. The results obtained were satisfactory in terms of precision (RSD <,5.7%) and accuracy (recovery >,89%). Thus, the method has demonstrated to be suitable for the qualitative and quantitative determination of synephrine, octopamine and tyramine in C. aurantium extracts, for dietary supplement quality control and for food adulteration identification. [source] Quantification of polyphenols with potential antioxidant properties in wines using reverse phase HPLCJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2008Neuza Paixćo Abstract A RP-HPLC method with photodiode array detection (DAD) was developed to separate, identify and quantify simultaneously the most representative phenolic compounds present in Madeira and Canary Islands wines. The optimized chromatographic method was carefully validated in terms of linearity, precision, accuracy and sensitivity. A high repeatability and a good stability of phenolics retention times (< 3%) were obtained, as well as relative peak area. Also high recoveries were achieved, over 80.3%. Polyphenols calibration curves showed a good linearity (r2 >0.994) within test ranges. Detection limits ranged between 0.03 and 11.5 ,g/mL for the different polyphenols. A good repeatability was obtained, with intra-day variations less than 7.9%. The described method was successfully applied to quantify several polyphenols in 26 samples of different kinds of wine (red, rosé and white wines) from Madeira and Canary Islands. Gallic acid was by far the most predominant acid. It represents more than 65% of all phenolics, followed by p -coumaric and caffeic acids. The major flavonoid found in Madeira wines was trans -resveratrol. In some wines, (,)-epicatechin was also found in highest amount. Canary wines were shown to be rich in gallic, caffeic and p -coumaric acids and quercetin. [source] Reversed-phase HPLC-ESI/MS analysis of birch leaf proanthocyanidins after their acidic degradation in the presence of nucleophilesPHYTOCHEMICAL ANALYSIS, Issue 5 2007Maarit Karonen Abstract Mountain birch leaves contain large amounts of structurally variable polymeric proanthocyanidins. Their isolation procedure was enhanced by the addition of liquid,liquid extractions prior to column chromatography over Sephadex LH-20. Isolated polymeric proanthocyanidins were depolymerised by acid-catalysis in the presence of benzyl mercaptan or phloroglucinol in order to study their composition. The resulting degradation products, flavan-3-ols and flavan-3-ol adducts, were analysed with reversed-phase high-performance liquid chromatography using UV photodiode array detection for quantification and electrospray ionisation mass spectrometry for identification. The results showed that polymeric proanthocyanidins contained (epi)gallocatechins and (epi)catechins as the extension units and, mainly, (+)-catechin as the terminal unit. The mean degree of polymerisation was found to be 26 based on thiolysis and 31 based on phloroglucinol degradation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Analysis of Rhizoma Polygoni Cuspidati by HPLC and HPLC-ESI/MSPHYTOCHEMICAL ANALYSIS, Issue 5 2007Tao Yi Abstract An HPLC method with photodiode array detection (PAD) and ESI/MS detection was developed for the qualitative and quantitative analysis of the major chemical constituents of the dried rhizome of Polygonum cuspidatum Sieb. et Zucc. (Rhizoma Polygoni Cuspidati; Chinese name Hu-Zhang). Based on the chromatographic separation on an Altima C18 column using 0.5% aqueous acetic acid and acetonitrile as the mobile phase, nine compounds, including stilbenes, stilbene glucosides, anthraquinones and anthraquinone glucosides, were identified by online ESI/MS analysis and seven were quantified by HPLC-PAD. A full validation of the method including sensitivity, linearity, repeatability and recovery was conducted. Linear calibration was achieved over the concentration range 1,200 mg/L with R2 > 0.999, whilst the limits of detection ranged from 0.51 to 1.57 ng. Repeatability was evaluated by intra- and inter-day assays and the RSD value was within 1.79%. Recoveries of the quantified compounds were within the range 96.0,100.1% with RSD values of less than 2.2%. Five samples of Rhizoma Polygoni Cuspidati from different regions were analysed using the developed method. The major constituents piceid, resveratrol, emodin-8- O - , - d -glucoside and emodin were selected to provide an index for the quality assessment of the herbal drug. Copyright © 2007 John Wiley & Sons, Ltd. [source] A high-throughput monolithic HPLC method for rapid Vitamin C phenotyping of berry fruitPHYTOCHEMICAL ANALYSIS, Issue 5 2006Paul G. Walker Abstract A rapid method for the quantification of ,ascorbic acid (1) in berry fruit by HPLC with photodiode array detection is presented. ,Ascorbic acid was resolved on a C18 monolithic column with aqueous buffer, after which the column was washed with acetonitrile to remove lipophilic compounds prior to re-equilibration for analysis of the next sample. Using the monolithic column format with high mobile phase flow rates, the entire separation, wash and re-equilibration were achieved in 3 min. With the exception of gooseberry (Ribes uva-crispa), for which an interfering compound co-eluted, concentrations of 1 could be determined in a wide range of berry fruits after extraction in metaphosphoric acid without further sample preparation. Using this extraction method, recoveries of 1 in excess of 85% were achieved. Fruit or juice extracts were stable in 5% metaphosphoric acid for at least 4 h and stability could be extended to longer than 150 h by the addition of the reducing agent tris(2-carboxethyl)phosphine hydrochloride. Following validation, the method was utilised for the phenotyping of fruit in a Scottish Crop Research Institute (SCRI) Ribes nigrum L. breeding population of 300 individuals. An improved extraction method allowed extraction, quantification of 1 and data analysis to be undertaken in less than one working week. Copyright © 2006 John Wiley & Sons, Ltd. [source] Isolation and characterisation of selected germander diterpenoids from authenticated Teucrium chamaedrys and T. canadense by HPLC, HPLC-MS and NMRPHYTOCHEMICAL ANALYSIS, Issue 4 2006P. Ramnathan Sundaresan Abstract Teucrium species, such as germander, are rich in neo -clerodane diterpenoids and have been used in traditional folk medicine for their stimulant, diuretic, antipyretic and antiseptic properties. However, the furano neo -clerodane diterpenoids present in germander have been implicated in the in vivo hepatotoxicity of this botanical. In this study, authenticated germander (Teucrium chamaedrys L. and Teucrium canadense L.) was used as the source material. Methanol extracts of powdered plant material were prepared and analysed by HPLC using Synergi® Max-RP columns with monitoring at 220 nm. Limited amounts of teucrin A and other diterpenoid standards were analysed on a Synergi Max-RP column in order to determine their retention times and to generate calibration curves. The same standards were subjected to concurrent mass spectral analysis. Teucrin A and diterpenoids such as dihydroteugin, teuflin, teuflidin and teucvidin were tentatively identified in the plant extracts by HPLC-MS and 1H-NMR experiments. For the isolation of teucrium diterpenoids on a semipreparative scale, a solid-phase extraction method was developed for the first time using styrene divinylbenzene and strata-X sorbents for teucrin A and teuflin, respectively. Semi-preparative HPLC of the methanol extract of the powdered aerial parts of Teucrium plants was carried out on a semipreparative Synergi Max-RP column with photodiode array detection in order to confirm the identities of some diterpenoids by HPLC-MS and NMR. Copyright © 2006 John Wiley & Sons, Ltd. [source] Determination of diarylheptanoids from Alpinia officinarum (lesser galangal) by HPLC with photodiode array and electrochemical detection,PHYTOCHEMICAL ANALYSIS, Issue 4 2005Zhihua Liu Abstract Normal-phase column chromatography followed by semi-preparative reversed-phase HPLC has been used to isolate, from the rhizomes of Alpinia officinarum, five diarylheptanoids identified as 5-hydroxy-7-(4,-hydroxy-3,-methoxyphenyl)-1-phenyl-3-heptanone, 5-methoxy-7-(4,-hydroxy-3,-methoxyphenyl)-1-phenyl-3-heptanone, 7-(4,-hydroxyphenyl)-1-phenylhept-4-en-3-one, 7-(4,-hydroxy-3,-methoxyphenyl)-1-phenyl-hept-4-en-3-one, 1,7-diphenylhept-4-en-3-one. The levels of these five diarylheptanoids in root material were determined quantitatively by HPLC with UV detection and the assay methods so developed were simple, rapid and accurate. Four of the diarylheptanoids could also be detected by HPLC with electrochemical detection (ECD) in the oxidative mode, and ECD was found to have a higher sensitivity than photodiode array detection. Copyright © 2005 John Wiley & Sons, Ltd. [source] Analysis of derivatized and underivatized theanine enantiomers by high-performance liquid chromatography/atmospheric pressure ionization-mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 2004Meera J. Desai Theanine, a naturally occurring non-proteinic amino acid found in tea leaves, has demonstrated wide-ranging physiological activity, from lowering blood pressure to enhancing the anti-tumor activity of chemotherapeutic drugs. The chiral nature of theanine suggests that enantiospecificity plays a significant role in its various pharmacological functions. Using the Chirobiotic T (teicoplanin) chiral stationary phase, native and derivatized theanine enantiomers were separated and detected via high-performance liquid chromatography (HPLC) coupled to atmospheric pressure ionization mass spectrometry (API-MS). With the use of flow rates compatible with each ionization source, native theanine standards achieved excellent sensitivity and detection limits (10,ng/mL) for both atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). Optimum sensitivity and detection limits for derivatized theanine standards were achieved using ESI-MS. The enantiomeric composition of six commercially available L -theanine samples was evaluated using the high-flow APCI-MS method and confirmed with photodiode array detection. Five of the six products contained significant amounts of D -theanine. Only one product, SunTheanine®, appeared to contain only the L -theanine enantiomer. Copyright © 2004 John Wiley & Sons, Ltd. [source] Simultaneous determination of eight major steroids from Polyporus umbellatus by high-performance liquid chromatography coupled with mass spectrometry detectionsBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Ying-yong Zhao Abstract Polyporus umbellatus is a widely used diuretic herbal medicine. In this study, a high-performance liquid chromatography coupled with atmospheric pressure chemical ionization,mass spectrometric detection (HPLC-APCI-MS) method was developed for qualitative and quantitative analysis of steroids, as well as for the quality control of Polyporus umbellatus. The selectivity, reproducibility and sensitivity were compared with HPLC with photodiode array detection and evaporative light scattering detection (ELSD). Selective ion monitoring in positive mode was used for qualitative and quantitative analysis of eight major components and ,-ecdysterone was used as the internal standard. Limits of detection and quantification fell in the ranges 7,21 and 18,63 ng/mL for the eight analytes with an injection of 10 µL samples, and all calibration curves showed good linear regression (r2 > 0.9919) within the test range. The quantitative results demonstrated that samples from different localities showed different qualities. Advantages, in comparison with conventional HPLC,diode array detection and HPLC-ELSD, are that reliable identification of target compounds could be achieved by accurate mass measurements along with characteristic retention time, and the great enhancement in selectivity and sensitivity allows identification and quantification of low levels of constituents in complex Polyporus umbellatus matrixes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Improved chromatographic fingerprints for facile differentiation of two Ganoderma spp.BIOMEDICAL CHROMATOGRAPHY, Issue 3 2009Chun-Mei Fu Abstract This paper addresses a comprehensive and comparative study of six phytochemical extraction methods for triterpenes from the fruiting body of Ganoderma spp. Quantitative analysis of extracts was performed by HPLC with photodiode array detection. In general, pressurized liquid extraction and microwave-assisted extraction under optimized conditions produce better yields, and the former also significantly reduces the total time of extraction and manipulation of a sample, as well as the amount of solvent used in comparison with conventional soxhlet, reflux, ultrasonic, and methanol,CO2 supercritical fluid extractions. Based on the improved extraction protocol, the fingerprinting profiles for two species of Lingzhi were established using the consistent chromatographic features of 12 authentic samples. Eleven common peaks of ganoderic/ganoderenic acids were identified using LC-ESI-MS-MS. These specific triterpene groups were adopted as chemical markers for Lingzhi. Using chemometric analysis, the developed fingerprinting was successfully applied to differentiate between the two species under the Ganoderma genus and is applicable as a method for quality evaluation of this valuable medicinal fungus and its related proprietary products. Copyright © 2008 John Wiley & Sons, Ltd. [source] High-performance liquid chromatographic method for identification and quantification of two isomeric coumarinolignoids,cleomiscosin A and cleomiscosin B,in extracts of Cleome viscosaBIOMEDICAL CHROMATOGRAPHY, Issue 11 2007Sunil K. Chattopadhyay Abstract A simple, accurate and reproducible reverse-phase HPLC method has been developed for identification and quantification of two isomeric coumarinolignoids, cleomiscosin A and B in different extracts of the seeds of Cleome viscosa using photodiode array detection at 326 nm. Cleomiscosin A and B were separated on a Waters symmetry C18 column (250 × 4.6 mm with 5.0 µm particle size) with an isocratic elution system composed of acetonitrile,methanol (1:2, v/v) and acetic acid,water (0.5:99.5, v/v) in the ratio of 40:60 (v/v). The calibration curves were linear (r2 > 0.997) in the concentration ranges of 20,100 µg/mL for both compounds. The limits of detection and quantification were 15 and 20 µg/mL for both cleomiscosin A and B. The intra- and inter-day precisions were 3.68 and 2.22% for cleomiscosin A and 4.22 and 5.06% for cleomiscosin B. The recoveries measured at two different concentration levels varied from 98.03 to 110.06%. The method was used to identify and quantify cleomiscosins A and B in different extracts of Cleome viscosa seeds. Copyright © 2007 John Wiley & Sons, Ltd. [source] Synthesis and analysis of aminochromes by HPLC-photodiode array.BIOMEDICAL CHROMATOGRAPHY, Issue 1 2003Adrenochrome evaluation in rat blood Abstract The catecholamine oxidation process induces cardiotoxicity and neurotoxicity. Catecholamines can oxidize to aminochromes through autoxidation or by enzymatic or non-enzymatic catalysis. Although some toxic effects seem to be related to the formation of aminochromes there is still scarce information concerning the identification and evaluation of these compounds in in vivo models. In this study five catecholamines were oxidized to their respective aminochromes: adrenaline/adrenochrome; noradrenaline/noradrenochrome; dopa/dopachrome; dopamine/dopaminochrome; and isoproterenol/isoprenochrome. The evaluation of the catecholamines oxidation profile was performed by HPLC with photodiode array detection and using either enzymatic (tyrosinase) or non-enzymatic [Ag2O, CuSO4, NaIO4 and K3Fe(CN)6] catalytic systems. The NaIO4 was found to be the most efficient oxidant of catecholamines. An isocratic reverse-phase HPLC method was developed to analyse each pair of catecholamine,aminochrome. The analytical system was then applied to the detection of adrenochrome in rat blood at 490,nm. Thus, adrenochrome was administered i.p. to rats and its concentration in whole blood was monitored after 5, 15 and 25,min. Blood treatment for adrenochrome evaluation consists of an acidification for protein precipitation followed by a rapid neutralization. The results showed a rapid decrease of adrenochrome concentration in blood after its administration. The adrenochrome present in blood was characterized by UV and tandem mass spectrometry. Copyright © 2002 John Wiley & Sons, Ltd. 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