Bensulfuron:preliminary test of photolysis.

Photodegradation 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

Identification of photoproducts from imazosulfuron by HPLC

Photolysis 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.

Seven 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

High-performance liquid chromatographic mass spectrometric identification of the photoproducts of cymoxanil.

The 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

Liquid chromatographic determination of nine N-methylcarbamates in drinking water.

A 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%

Analysis of Calcium Channel Blocking Dihydropyridines and their degradation products by Gas Chromatography

Seven 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

Analysis of calcium channel blocking dihydropyridines by high performance liquid chromatography.

Nine dihydropyridine calcium blockers have been analyzed by HPLC .Symultaneous analysis has been performed both using different isocratic conditions and linear gradient method . The influence of pH and ionic strength of the mobile phase on separation mechanism is discussed. Moreover, the separation ability of original compounds from daylight degradation products has been studie

Photodegradation of bensulphuron methyl in aqueous solution

Photodegradation of bensulphuron methyl, (methyl -(4,6-dimethoxypyrimidin-2-carbamoylsulphamoyl)-o-toluate ester) was carried out in aqueous solution under UV light. The rate of photolysis followed first-order kinetics, with a half-life of 31.7 min at λ = 254 nm and 41.3 h at λ ≥ 290 nm, with significant correlation coefficients (0.9898 and 0.9625, respectively). The main photoproducts in distilled water were identified with a diode array detector and mass spectrometry. The results indicate that different reaction pathways are followed: cleavage of the sulphonylurea bridge, desulphonylation, which can proceed either by a carbon-sulphur cleavage or a nitrogen-sulphur cleavage and contraction of the sulphonylurea bridge. A mechanism which accounts for the formation of the photoproducts is propose

High performance liquid chromatographic analysis of quinolone antibacterial agents.

Eleven 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

Determination of neonicotinoid insecticides residues in bovine milk samples by solid-phase extraction clean-up and liquid chromatography with diode-array detection

In this paper we have developed an analytical method for the simultaneous determination of four nicotinoid insecticides [acetamiprid (ACT), imidacloprid (ICL), thiacloprid (TCL) and thiamethoxam (TMX)] in bovine whole milk. These analytes were extracted, in a single step with dichloromethane, from fortified milk samples, using Chem Elut cartridges, containing diatomaceous earth material. Insecticide's determination and quantification were performed by HPLC with diode-array detection (DAD). Average recoveries of the four insecticides from bovine milk samples were between 85.1 and 99.7% at spiking levels 0.01, 0.05 and 0.1mgkg(-1). Relative standard deviations (RSDs) were no larger than 10% for all of the recovery tests. The calculated limits of quantitation (LOQ) ranged from 0.01 to 0.04mgkg(-1) for the four insecticides, being equal to or lower than the maximum residue limits (MRLs) established by European legislation (0.01-0.05mgkg(-1)). The developed method is linear at concentrations within the tested interval, with coefficients of determination higher than 0.9990. According to Commission Decision 2002/657/EC, decision limit (CCalpha) and detection capability (CCbeta) have been calculated. The proposed method is rapid, simple and could be utilized for the routine analysis of pesticides residues