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12th International Conference on Flow Injection Analysis

作者： van Staden, JF Stefan, RI Univ Pretoria Dept Chem ZA-0002 Pretoria South Africa

The simplicity of the sequential injection (SIA) manifold and its low need for maintenance makes it an ideal tool in speciation. As miniaturization and reduction of reagent consumption are also ultimate goals in chemical sensing, it is useful to review the use of combined injection and programmed flow as a central issue in designing SIA systems with chemical sensors and structurally simplified chemical analysers. This overview gives an insight into the current state, analytical scope and performance characteristics of sequential injection systems as analytical tools for speciation. The suitability of SIA for speciation analysis is illustrated by the methods used in the conduits of sequential injection systems for the chemical conversion of different chemical forms into detectable chemical species. Configurations of the basic sequential injection speciation analysis systems were designed around a multi-syringe-time-based-injection system with one detector, direct and indirect speciation of different forms using a single detector including diode array detection and direct speciation of different forms using multiple detection. Examples showing the use of SIA for the simultaneous determination or speciation of metal ions, inorganic anions and organic compounds are given with some recent results from our research groups. (C) 2004 Elsevier B.V. All rights reserved.

关键词： sequential injection miniaturization diode array detection

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Evaluation of different detection modes for the analysis of procyanidins in leaves and flowers of Crataegus spp.: Part I.: diode array and electrochemical detection

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PHYTOCHEMICAL ANALYSIS 2000年第2期11卷 106-112页

作者： Rohr, GE Meier, B Sticher, O ETH Zurich Dept Pharm CH-8057 Zurich Switzerland Zeller AG CH-8590 Romanshorn Switzerland

diode array and single electrode electrochemical detection were evaluated for their use in the analysis of (-)-epicatechin and oligomeric procyanidins in reference solutions and extracts of leaves and flowers of Crataegus spp, Linearity of regression curves was good for both detection modes. diode array detection was found to be more selective but less sensitive than electrochemical detection, The absorbance ratio 220/280 nm gives information on the degree of polymerization in reference solutions, In the presence of matrix no additional structural information can be obtained from the absorbance ratios due to high standard deviations. Quantitative evaluation in terms of monomer equivalents using electrochemical detection leads to an underestimation of the contents of procyanidin dimers, but it is applicable using detection at 280 nm, in view of the better selectivity and the easier handling, diode array detection is recommended for the analysis of procyanidins in complex matrices. Copyright (C) 2000 John Wiley & Sons, Ltd.

关键词： liquid chromatography electrochemical detection diode array detection flavan-3-ols procyanidins Crataegus

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Characterisation of the ester-substituted products of the reaction of p-t-butyl calixarene and ethyl bromoacetate using LC-UV-MS and LC-DAD

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TALANTA 2002年第6期57卷 1119-1132页

作者： McMahon, G Wall, R Nolan, K Diamond, D Dublin City Univ Natl Ctr Sensor Res Dublin 9 Ireland

A series of derivatisation reactions between p-t-butyl calix[4]arene and ethyl bromoacetate were carried out in order to prepare 1,3 diester substituted calix[4]arene. Mass spectral data, obtained from direct injection of samples, indicated that the reactions were rich in the desired product. Since the ultra violet (UV) spectra of the desired product and possible impurities are very similar, liquid chromatography (LC) chromatographic data seemed to corroborate these results. However, when on-line LC-UV-MS was carried out and each LC peak subjected to MS analysis as it eluted, a very different picture emerged. It was found that many of these reactions actually contained high levels of the monoester product which, having less affinity for sodium in the MS, is therefore seriously underestimated in any direct injection assay. LC-diode array detection (DAD) methods were also used to help successfully identify and characterise the compounds being formed in these complex reactions. The overall results obtained in this paper allowed the optimal reaction conditions to be determined for this reaction. LC-MS analysis of the chromatographic peaks also identified the presence of two isomers of the diester substituted calix[4]arene (1,3 and 1,2 diesters). The combination of LC and UV/MS detection is required for accurate analysis of the products of such reactions. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词： calix[4]arene liquid chromatography mass spectrometry diode array detection

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Evaluation of niacin LC methods by diode array/spectral analysis

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ANALYTICAL LETTERS 2002年第13期35卷 2173-2184页

作者： Lacroix, DE Wolf, WR Hindsley, TM USDA Beltsville Human Nutr Res Ctr Food Composit Lab Beltsville MD 20705 USA

Three extraction/LC methods for the determination of niacin in food materials have been qualitatively evaluated by spectral analysis procedures using a photodiode array detection system. This system allows visual inspection of multiple wavelength scans to identify presence of multiple components under LC peaks. It also allows calculation of a Similarity Index (SI) by means of library match software that compares the spectra of a LC peak to that of a standard sample. Niacin can occur in;foods either as nicotinic acid or often as added nicotinamide to enrich foods. We have evaluated LC methods for determination of both forms of niacin in several reference materials: SRM 1846 Infant Formula (NIST), RM 8437. Hard Red Spring Wheat (NIST), and VMA 195 Cereal (AACC). Spectral analysis showed only the niacin vitamer with a library match having a SI > 0.99 (1.0 is a perfect match) for nicotinic acid by anion exchange LC using an aromatic sulfonic acid-cation exchange solid phase extraction following a standard H2SO4 digest, and for nicotinamide using a trichloroacetic acid (TCA) extraction followed by reverse phase (RP) LC. A method involving meta-phosphoric acid (m-PA) extraction followed by RP/LC is not as satisfactory;while the 3-D view is not conclusive for a multiple component peak, the library match indicates a significantly lower SI of 0.81. Utilization of spectral analysis software with library matching is a useful tool for evaluating a variety of LC protocols. More robust LC methods for determining niacin in foods can replace laborious microbiological methods currently used by food testing laboratories. These LC methods combined with use of appropriate reference materials can provide definitive data for niacin in foods to be incorporated in food compositional tables, for use in food labeling and by dieticians preparing formulated diets.

关键词： niacin nicotinic acid nicotinamide spectral analysis liquid chromatography diode array detection

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Simultaneous analysis of six antiepileptic drugs and two selected metabolites in human plasma by liquid chromatography after solid-phase extraction

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ANALYTICA CHIMICA ACTA 2002年第1-2期472卷 1-10页

作者： Bugamelli, F Sabbioni, C Mandrioli, R Kenndler, E Albani, F Raggi, MA Univ Bologna Dept Pharmaceut Sci I-40126 Bologna Italy Univ Vienna Inst Analyt Chem A-1090 Vienna Austria Univ Bologna Dept Neurol Sci I-40123 Bologna Italy

A rapid and simple liquid chromatographic method with photodiode array detection was developed for the simultaneous determination of six antiepileptic drugs (oxcarbazepine, carbamazepine, lamotrigine, phenobarbital, primidone and phenytoin) and two metabolites (10, 11 -dihydro- 10-hydroxycarbamazepine and 10, 11 -dihydro-10-hydroxycarbamazepine, the main active metabolites of carbamazepine and oxcarbazepine, respectively) in human plasma. Separation of the analytes was achieved in less than 11.5 min on a C18 column (150 x 4.0mm, i.d. 4.5 mum) with a mobile phase composed of methanol, acetonitrile and a pH 3.0, 15 mM phosphate buffer containing 0.63% triethylamine (19.2:16.8:64.0, (v/v/v)), at 1 ml min(-1) flow rate. Two procedures were tested for the pretreatment of human plasma samples: protein precipitation with perchloric acid, and solid-phase extraction. The protein precipitation procedure did not allow for the analysis of 10, 1 1-dihydro-10, 11-epoxycarbamazepine. On the contrary, solid-phase extraction with hydrophilic-lipophilic balance cartridges gave good results in terms of extraction efficiency and reproducibility and allowed for the determination of all analytes. The HPLC-DAD method developed, coupled to a careful SPE procedure, seems to be suitable for the plasma level determination of simultaneously administered antiepileptic drugs. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词： antiepileptic drugs liquid chromatography solid-phase extraction human plasma diode array detection

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Determination of histamine in fish products by capillary electrophoresis and ion-pair liquid chromatography with diode-array detection

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JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 1999年第1期79卷 91-94页

作者： Gardana, C Pietta, P Ciappellano, S Testolin, G CNR ITBA DISTAM Sez Nutr I-20133 Milan Italy

A method for histamine determination in fish and fish products by capillary electrophoresis and ion-pair liquid chromatography has been developed. Histamine was extracted from different fish samples with 10% trichloroacetic acid, and the filtrate was directly applied to capillary electrophoresis apparatus. A preliminary purification through a solid phases extraction cartridge (Sep-pak C-18) was necessary for HPLC analysis. Histamine was detected 'on-line' at 210nm by both approaches. HPLC procedure allowed accurate (+/-2.2%) and repeatable (+/-1.6%) determination of histamine in fish products at appropriate levels (20-100 mg kg(-1)) to meet current regulations. (C) 1999 Society of Chemical Industry.

关键词： histamine fish capillary electrophoresis HPLC diode array detection solid phase extraction

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Chromatographic and spectral analytical data for the determination of benzodiazepine abuse in methadone maintenance program

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TALANTA 2001年第4期55卷 721-732页

作者： Diallo, S Bugni, E Senhadj-Raoul, F Gasdeblay, S Marot, D Dessalles, MC Mahuzier, G Psychiat Hosp Paul Guirand Biol Lab F-94800 Villejuif France Fac Pharm Chatenay Malabry Dept Analyt Chem F-92290 Chatenay Malabry France

Benzodiazepines are some of the most often co-abused substances in methadone treatment. Their identification in biological samples is of great importance in toxicological screening and in methadone maintenance program. The aim of this report is to describe, the analytical data making possible the identification of benzodiazepines and/or metabolites using a reversed phase liquid chromatography coupled with diode array detection. (C) 2001 Elsevier Science B.V. All rights reserved.

关键词： benzodiazepines liquid chromatography diode array detection UV spectra analysis

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Fast separation of terbinafine and eight of its metabolites by capillary electrophoresis

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JOURNAL OF SEPARATION SCIENCE 2001年第4期24卷 265-270页

作者： Crego, AL Gómez, J Lavandera, JL Univ Alcala Fac Quim Dept Quim Analit Madrid 28871 Spain GlaxoWellcome Ctr Invest & Desarrollo Dept Quim Estructural Madrid 28760 Spain

A rapid and simple capillary zone electrophoresis (CZE) method for the determination of terbinafine and eight of its main metabolites after incubation with rat hepatic S9 fraction was developed. The effect of the concentration and type of the running electrolyte as well as of the addition of an organic solvent were studied with emphasis on selectivity and sensitivity. All nine components obtained (unmetabolized terbinafine and up to eight of its metabolites) are baseline resolved in less than 4 minutes using a 0.05 M phosphate buffer (pH 2.2) without additives, after a solid-phase clean-up procedure of these in-vitro samples. In addition, under the conditions described, no endogenous components of the sample interfere at the detection wavelength chosen. After optimization of the separation conditions, some analytical characteristics of the developed CZE method were investigated. A limit of detection of only 0.08 mug/mL was obtained for terbinafine using a standard solution. Finally, the use of on-line CZE/ diode array detection enabled to identify tentatively the presence of unmetabolized parent terbinafine and its metabolites in the mixture of nine components separated.

关键词： terbinafine drug metabolites in-vitro analysis capillary zone electrophoresis diode array detection

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Presence of carbamate pesticides in environmental waters from the northwest of Mexico:: Determination by liquid chromatography

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WATER RESEARCH 2001年第8期35卷 1933-1940页

作者： De Llasera, MPG Bernal-González, M Univ Nacl Autonoma Mexico Fac Quim Lab Tecnol Limpias 201B Mexico City 04510 DF Mexico

A study on the presence of carbamate pesticides, namely aldicarb, aldicarb sulfoxide, baygon, benthiocarb, carbofuran, 3-hydroxycarbofuran, carbaryl, desmedipham, methiocarb. methomyl, thiodicarb, oxamyl, and propham was made in ground and surface waters from an agricultural zone of the Yaqui Valley located in northwest Mexico. Trace determinations were made bq liquid chromatography (LC) with post-column fluorescence detection (EPA method 531.1) or LC-diode array UV detection coupled on-line to a solid-phase extraction (SPE) system and using a 13 x 4.6 mm i.d. precolumn and a 150 x 4.6mm i.d, analytical column, both packed with a C18 silica. Results indicated that the level of contamination with methiocarb was 5.4 mug/L in a groundwater sample and that for 3-hydroxycarbofuran was 18 mug/L in a surface water sample. This study provides the basis for a future monitoring program. (C) 2001 Elsevier Science Ltd. All rights reserved.

关键词： carbamate pesticides liquid chromatography on-line solid-phase extraction water pollution multi-residue analysis fluorescence detection diode array detection

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Color stability of commercial anthocyanin-based extracts in relation to the phenolic composition. Protective effects by intra and intermolecular copigmentation

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JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2001年第1期49卷 170-176页

作者： Malien-Aubert, C Dangles, O Amiot, MJ UAPV INRA UMR F-84914 Avignon 9 France CHR Hansen SEFCAL F-30760 St Julien de Peyrolas France

Anthocyanin extracts are increasingly used as food ingredients. A current challenge is to maintain their color properties. The stability of some colorants has been studied in sugar and non-sugar drink models at three pH values (3, 4, and 5) under thermal and light conditions simulating rapid food aging. At a given pH, color stability mainly depends on the structures of anthocyanins and of colorless phenolic compounds. Colorants rich in acylated anthocyanins (purple carrot, red radish, and red. cabbage) display great stability due to intramolecular copigmentation. The protection of red chromophore is higher for diacylated anthocyanins in red radish and red cabbage. For colorants without acylated anthocyanins (grape-marc, elderberry, black currant, and chokeberry), intermolecular copigmentation plays a key role in color protection. Colorants rich in flavonols and with the highest copigment/pigment ratio show a remarkable stability. By contrast, catechins appear to have a negative effect on red colorants, quickly turning yellowish in drink models. This effect is more pronounced when the pH is increased. Finally, color does not seem to be greatly influenced by the addition of sugar.

关键词： colorants anthocyanins flavonols flavanols phenolic acid CIELAB spectrophotometry HPLC diode array detection color stability copigment effect

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