Degradation of imazosulfuron in different soils-HPLC determination

Imazosulfuron, 1-(2-chloroimidazo [1,2-a] pyridin-3-ylsulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl)urea, is a new sulfonylurea herbicide applied once per growing season. It is highly active at low application levels and is used to control most annual and perennial broad-leaf weeds and some grasses in cereal crop. In this work the degradation of imazosulfuron in four different soils was investigated under aerobic laboratory conditions to evaluate its environmental fate. Test soils were treated with this herbicide in acetonitrile to obtain a final concentration of 0.2 mg kg(-1) (100 g ha(-1)), extracted with methylene chloride and analyzed by reversed-phase liquid chromatography (RP-HPLC) using a C(18) column coupled with UV detection. Recoveries of spiked soils ranged from 84.3 to 99.8% (RDS 0.0-4.9%; n = 4). The limits of quantitation ranged from 0.002 to 0.004 mg kg(-1). Imazosulfuron half-life, t(1/2), was calculated in each of the investigated soil. In aerobic conditions it ranged between 1 and 50 days.     

Ion trap tandem mass spectrometry study of dexamethasone transformation products on light activated TiO2 surface

The photocatalytic transformation of dexamethasone and the formation of its intermediate compounds have been studied using titanium dioxide as a photocatalyst. The degradation of dexamethasone occurs easily through the formation of several hydroxy derivatives whose characterization has been made by HPLC/MS/MS. Even if both oxidative and reductive processes can be operating, only oxidative products have been identified in air saturated aqueous suspensions. A pattern of reaction pathways accounting for the observed intermediates is proposed. The obtained experimental evidence may be rationalized postulating the existence of a double initial mechanism. A single oxidation step resulting from the attack by one ·OH radical leading to the formation of five hydroxy-derivatives and a concomitant attack involving two ·OH radicals leading to the hydroxylation of the quinoid moiety of the molecule.     

Determination of aflatoxins in peanuts, maize feed and whole milk by HPLC-MS2 and MS3 tandem mass spectrometry

A method is presented for the detection of six toxins of fungal origin in various foods: peanuts, a sample of maize feed and whole milk. Extraction and HPLC-APCI-MS detection were discussed. The performances of MS/MS, MS3 and SRM detection modes were checked and best conditions of sensitivity were obtained in MS/MS mode.     

Ion trap tandem mass spectrometry study of dexamethasone transformation products on light activated TiO2 surface

The photocatalytic transformation of dexamethasone and the formation of its intermediate compounds have been studied using titanium dioxide as a photocatalyst. The degradation of dexamethasone occurs easily through the formation of several hydroxy derivatives whose characterization has been made by HPLC/MS/MS. Even if both oxidative and reductive processes can be operating, only oxidative products have been identified in air saturated aqueous suspensions. A pattern of reaction pathways accounting for the observed intermediates is proposed. The obtained experimental evidence may be rationalized postulating the existence of a double initial mechanism. A single oxidation step resulting from the attack by one ·OH radical leading to the formation of five hydroxy-derivatives and a concomitant attack involving two ·OH radicals leading to the hydroxylation of the quinoid moiety of the molecule.     

Simultaneous effect of salt and methanol concentrations on the hydrophobicity of some ion-pairing agents

Summary The lipophilicity (hydrophobicity) of some alkylamines and arylamines was determined with reversed-phase thin-layer chromatography using various water: methanol mixtures as eluent with and without adding salt to the system. The effect of various structural parameters of amines and that of the chromatographic conditions were assessed with stepwise regression analysis. The calculation proved that in case of alkylamines the lipophilicity does not depend linearly on the length of the alkyl chain, the effect of methanol and salt concentrations are intercorrelated and the influence of the alkyl chain branching is negligible. In case of arylamines the number of amino groups has the highest impact on the retention and the effect of methanol and salt is also intercorrelated.