Search results for "Reagent"
showing 10 items of 699 documents
Preparation methods to optimize the performance of sensor discs for fast chemiluminescence ozone analyzers.
2013
Fast ozone (O(3)) measurements (1-50 Hz) in the atmosphere are required for airborne studies and for the measurement of ground-based O(3) fluxes by the eddy covariance technique. Fast response analyzers, based on heterogeneous chemiluminescence, need dye coated sensor discs on which the chemiluminescence is generated. In this study, we present three new preparation methods for those sensor discs. Currently available sensor discs exhibit a fast temporal decay of sensitivity, resulting in short duty times which is troublesome for many field applications. To produce sensor discs that provide more stable signals over time, three dyes and nine energy transfer reagents were tested (as well as dif…
Performance of porous silica layers in open-tubular columns for liquid chromatography
1989
Abstract Progress has been made in the preparation of porous silica layers in fused-silica capillaries for open-tubular liquid chromatography. The porous silica layer is prepared by (i) static coating of the silica precursor, polyethoxysiloxane (PES), followed by (ii) converting the PES film into a porous silica layer with ammonia solution. The porous silica layer can be easily modified by silane reagents commonly used in packed column high-performance liquid chromatography. The performance of the silica layer with the different phase systems was tested with polyaromatic hydrocarbons and derivatized amino acids as samples.
Assessment of exposure to environmental tobacco smoke in young adolescents following implementation of smoke-free policy in Italy.
2009
We investigated acute and chronic exposure to environmental tobacco smoke (ETS) in a cohort of young adolescents using urinary cotinine and hair nicotine testing after recent implementation of Italian smoke free legislation. Study subjects were 372 Italian young adolescents, between 10 and 16 years of age from the principal city of Sicily, Palermo. Urine and hair samples were collected between November 2005 and May 2006, when the legislation to ban smoking in all the enclosed places of employment (including bars, restaurants, pubs) was completely enforced. An exhaustive questionnaire including sociodemographic characteristics and active and passive exposure to cigarette smoking was complete…
Bloodstains on Leather: Examination of False Negatives in Presumptive Test and Human Hemoglobin Test.
2017
Presumptive tests for blood are very simple and sensitive tests used in the search for evidence. They also provide initial information on the nature of stains. A second test can confirm their nature. However, these tests can present false–negative results for different reasons. Some of those reasons have been studied, while others, those caused by the substrate material that contains the stain, are less well known. This work studies the effect of one component of a leather substrate—quebracho extract—on presumptive and human hemoglobin blood tests. Assays were performed using samples of blood dilutions contaminated with quebracho extract and others formed on a substrate containing the conta…
Iron-Catalyzed Cross-Coupling Reactions of Alkyl Grignards with Aryl Chlorobenzenesulfonates
2021
Aryl sulfonate esters are versatile synthetic intermediates in organic chemistry as well as attractive architectures due to their bioactive properties. Herein, we report the synthesis of alkyl-substituted benzenesulfonate esters by iron-catalyzed C(sp2)–C(sp3) cross-coupling of Grignard reagents with aryl chlorides. The method operates using an environmentally benign and sustainable iron catalytic system, employing benign urea ligands. A broad range of chlorobenzenesulfonates as well as challenging alkyl organometallics containing β-hydrogens are compatible with these conditions, affording alkylated products in high to excellent yields. The study reveals that aryl sulfonate esters are the m…
Isomerization and Application of Aroylnorbornenecarboxylic Acids for Stereoselective Preparation of Heterocycles
2002
When boiled in acidic or basic solution, diendo-3-aroylbicyclo[2.2.1]heptane-2-carboxylic acids (1 and la) isomerize to exo-3-aroylbicyclo[2.2.1]heptane-endo-2-carboxylic acids (2 and 2a). Similar endo→exo and even exo → endo isomerization of the aroyl group occurred when the Diels-Alder product containing a mixture of 3-exo-p-toluoylbicyclo[2.2.1 ]hept-5-ene-2-endo-carboxylic acid (4) and 3-endo-p-toluoylbicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid (5) was reacted with bifunctional reagents: o-aminothiophenol, 3-amino-1-propanol, 1,4-diaminobutane or diexo-3-hydroxymethylbicyclo[2.2.1]heptane-2-amine. All the reactions yielded mixtures of norbornene diendo- and diexo-fused heterocycles (…
Comparison of Methods and Kits for Colorimetric Determination of Residual Chlorine in Water
1997
Abstract The use of 3,3',5,5'-tetramethylbenzidine (TMB) for residual chlorine determination in water offers 2 possibilities, one at pH 1-2 and absorbance measurement at 450 nm and another at pH 3.8-5.8 and measurement at 650 nm. The reaction of chlorine with TMB reaches its maximum sensitivity at pH 1-2. The detection limit is 2 ng/mL. A calibrated scale for colorimetric determination of residual chlorine in water with 3,3',5,5'-tetramethylbenzidine (TMB), prepared with tropaeolin O (C.I. 14270), is described. This scale is stable for several months and can be useful in replacing the conventional and much less stable scale prepared from standard solutions of oxochlorate (I). Kits for deter…
Inhibition of molybdenum blue formation by ATP.
1981
Molybdenum blue formation was not affected by the presence of ATP up to a concentration of 1.2 muM/l. At higher concentrations the color development was inhibited relative to ATP concentration, finally reaching complete inhibition. Auto-hydrolysis of ATP was found at a rate of 1.4%/h. An exact determination of inorganic phosphate in the presence of easily hydrolyzed phosphate esters requires the measurement of extinction at fixed time intervals and extrapolation back to time zero.
Characterizing the interaction between enantiomers of eight psychoactive drugs and highly sulfated-β-cyclodextrin by counter-current capillary electr…
2013
The estimation of apparent binding constants and limit mobilities of the complexes of the enantiomers that characterize the interaction of enantiomers with chiral selectors, in this case highly sulfated β-cyclodextrin, was approached using a simple and economic electrophoretic modality, the complete filling technique (CFT) in counter-current mode. The enantiomers of eight psychoactive drugs, four antihistamines (dimethindene, promethazine, orphenadrine and terfenadine) and four antidepressants (bupropion, fluoxetine, nomifensine and viloxazine) were separated for the first time for this cyclodextrin (CD). Estimations of thermodynamic and electrophoretic enantioselectivies were also performe…
Synthesis of hexahydrocyclopenta[ij]isoquinolines as a new class of dopaminergic agents.
2014
In this study, we have described the synthesis of the tricyclic 1,2,3,7,8,8a-hexahydrocyclopenta [ij]isoquinoline (HCPIQ). Herein, six differently substituted 5,6-dioxygenated-7-phenyl-HCPIQs have been synthesized using a new methodology via (E)-1-styryl-THIQ by Friedel-Crafts cyclization with Eaton's reagent. Results showed that HCPIQs (3, 3a-e) displayed a moderate affinity for D1 dopamine receptors (DR) in the micromolar range, furthermore the catecholic HCPIQs 3a (NH), 3c (NCH3) and 3e (NCH2CHCH2) exhibited outstanding affinity and high selectivity towards D2 DR. Indeed, 3a, 3c and 3e showed Ki values of 29 nM, 13 nM and 18 nM, respectively, and HCPIQs 3a (NH) and 3c (NCH3) displayed a …