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Analysis of Calcium Channel Blocking Dihydropyridines and their degradation products by Gas Chromatography
No full textSeven dihydropyridine calcium blockers have been analyzed by GC. Simultaneous analysis has been performed both by an isothermal and a gradient method. Moreover, the proposed methods have been performed on the analysis of daylight exposed methanolic solutions of considered compounds; the ability of the systems in separate original compounds from daylight degradation products has been studied. The GC-MC spectra of photodegradation products are discussed
Liquid chromatographic determination of nine N-methylcarbamates in drinking water.
No full textA multi-residue method for the simultaneous extraction from drinking water using solid-phase extraction on LiChrolut EN [poly(styrene-divinylbenzene), PSDVB] and determination of nine N-methylcarbamate pesticides (NMCs) (aldicarb, its metabolites i.e. aldicarb sulfone and aldicarb sulfoxide and carbaryl, carbofuran, dioxacarb, ethiofencarb, methomyland propoxur) using reversed-phase liquid chromatography was studied. A 1000-fold pre concentration was achieved and the method was used for determination of the nine pesticides in water, with limits of detection in the range 3–15 ng L−1. For all compounds the recoveries determined at the 0.1 and 1 μg L−1 level generally ranged from 85 to 104% with relative standard deviations (RSD) of 1.4–8.8%
High-performance liquid chromatographic mass spectrometric identification of the photoproducts of cymoxanil.
No full textThe photochemical degradation of the fungicide cymoxanil {2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino) acetamide} was studied in aqueous buffer solution (pH 5.9 ± 0.1) under UV light and in laboratory conditions. The degradation followed a pseudo-first-order kinetic with significant correlation coefficient. The main photoproducts were separated and tentatively identified by HPLC/UV and HPLC/MS data, as 3-ethyl-4-(methoxyamino)-2,5-dioxo-4-imidazolidinecarbonitrile, 1-ethyl-5-(methoxyimino)-2,4-imidazolidin-2,4-dione, ethylimidazolidinetrione and {[(ethylamino)carbonyl]-amino}oxoacetic acid. A photolysis pathway of cymoxanil is proposed
Identification of photoproducts from imazosulfuron by HPLC
No full textPhotolysis of imazosulfuron was studied in aqueous solution under UV light. The reaction followed a pseudo-first-order kinetic with significant correlation coefficient. The major photodegradation products of imazosulfuron after irradiation under UV light were separated and tentatively identified by HPLC-MS analysis as (4,6-dimethoxypyrimidine-2-yl)aminocarbonylsulfamic acid, 4,6-dimethoxy-2-ureidopyrimidine and 2,2'-dichloro-[3,3'] bi [imidazo[1,2-a] pyridinyl]. The results indicate that different reaction pathways are followed: (1) cleavage of the sulfonylurea bridge; (2) desulfonylation, which can proceed either by a carbon-sulfur cleavage or a nitrogen-sulfur cleavage. A mechanism for the formation of the photoproducts is proposed
Analysis of ACE inhibitor drugs by high performance liquid chromatography.
No full textSeven angiotensin-converting-enzyme (ACE) inhibitors have been analyzed by HPLC. The influence of different organic modifiers and counter-ions in the eluent at different pH values have been investigated allowing the identification of the best experimental conditions for the analysis of these compounds. The sinergic effect of TEA and propanol in the eluents resulted as a critical factor to obtain satisfactory peak shapes and resolution
Bensulfuron:preliminary test of photolysis.
No full textPhotodegradation of bensulfuron methyl, ( methyl-alfa-4,6-dimethoxypyrimidin-2-carbamoylsulfamoyl)-o-toluate ester) was carried out in aqueous solution under UV light. The rate of photolysis followed a first order kinetic. The main metabolites in distilled were tentatively idenified with a Diode Array Detector (DAD) and mass spectometry (MS) as (4,6-dimethoxy-2-pyrimidinyl)urea (1), methyl-alfa-4,6-dimethoxy-2-pyrimidinyl)amino-o-toluate 4) and alfa-sulfamoyl-o-toluic acid (2) that cyclises to 2-mthylsulfonylbenzoic acid imine (3). A mechanism which accounts for the formation of photoproducts is propose
High performance liquid chromatographic analysis of quinolone antibacterial agents.
No full textEleven quinolone antibacterials have been analyzed by HPLC. The effects of different pH values and organic modifiers on chromatographic behaviour are discussed. Moreover the influence on separation mechanism of different counter-ions at various concentrations in the eluent has been investigated. Two different chromatographic methods have been selected, that allow the simultaneous analysis of quinolones containing or not a piperazinyl moiety, respectively
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