An ultrasensitive method for the determination of thiouracil and phenylthiouracil using capillary zone electrophoresis and laser-induced fluorescence detection

This paper reports the development of a method based on capillary electrophoresis with laser-induced fluorescence detection for the simultaneous determination of thiouracil (TU) and phenylthiouracil (PhTU) with high sensitivity (nanomolar range, i.e., attomoles detected). After derivatization with 5-iodoacetamidofluorescein, the analytes were separated by capillary zone electrophoresis using 20 mM phosphate buffer (pH 10.0) and quantified by fluorescence detection. The linearity range, precision, recovery, and detection limits were determined, and the method was shown to be applicable for the determination of TU and PhTU in spiked feed samples and urine.     

Stereoselective Synthesis of Tetrahydrofuran Spiro‐β‐Lactams by Ru‐Catalyzed Metathesis of 7‐Oxabicyclo[2.2.1]heptenes

A new method for the synthesis of spiro‐β‐lactams tethered to tetrahydrofuran rings is described. The procedure is based on Ru‐catalyzed metathesis sequences with oxanorbornene precursors easily obtained by the Staudinger [2+2] cycloaddition of related imines.     

Simple and rapid micellar electrokinetic capillary chromatographic method for simultaneous determination of four antiepileptics in human serum

A very rapid and simple MEKC method was developed for the simultaneous determination of four antiepileptic drugs, ethosuximide (Etho), primidone (Pri), phenytoin (Pht) and carbamazepine (Cbz) in human serum. Sample analysis required only 100 microL of human serum which only needed to be centrifuged, decanted and combined with the running buffer [5.3 mM Na(2)HPO(4)/3.2 mM borax buffer (pH 9.5) containing 55 mM SDS and 3.5% (v/v) acetone]. The analysis was performed in only 10 min into fused-silica capillaries (57 cm total length with 50 microm i.d. and 50 cm to the detector) using the MEKC methodology with diode-array detection at 220 nm. The calibration graphs were established for ethoximide, primidone, phenytoin and carbamazepine between 0 and 20 mg/L. Recoveries were between 85 and 87%. The simplicity of the proposed methodology makes it suitable for routine clinical use, especially for epileptic patients on polytherapy.     

Di-2-pyridylmethylamine-based palladium complexes as new catalysts for Heck,Suzuki, and Sonogashira reactions in organic and aqueous solvents

A new palladium-dipyridylmethylamine complex is an excellent catalyst for C-C bond-forming processes such as the Heck, Suzuki, and Sonogashira reactions in organic and aqueous solvents under homogeneous conditions. [reaction: see text]     

A fluorimetric study of pindolol and its complexes with cyclodextrins

Spectrofluorimetric characteristics of pindolol have been investigated with the aim of using this technique for analytical determinations. Other monosubstituted indole derivatives, 4-methoxy and 5-methoxyindole, have been also studied for comparative purposes. Corrected excitation and emission wavelengths in different solvents are reported and the effect of solvent on the Stokes shifts of these compounds has been analysed using the Lippert equation. In addition, the Stokes shift of pindolol has been determined in dioxan-water solvent mixtures and the presence of specific solvent effects is discussed. The fluorescence of pindolol is pH dependent, the quantum yields determined in water are lower than those in other solvents. With respect to the sensitivity, it has been found that the detection limits in aqueous solutions are improved in the presence of beta and methyl-beta-cyclodextrin. Finally, a fluorimetric analysis of the interaction between pindolol and different cyclodextrins has been carried out in order to determine the apparent stability constants of the complexes and the thermodynamic parameters associated to complexation.     

Liquid chromatography with ultraviolet absorbance detection for the analysis of tetracycline residues in honey

The separation of tetracyclines (TCs) using reversed-phase liquid chromatography (LC) is proposed. The use of an amide-based stationary phase prevents the interaction of tetracyclines with the residual silanol groups and thus avoids the appearance of tailed peaks. Detection was based on using an UV spectrophotometer and gradient elution with acetonitrile-oxalic acid as mobile phase permitted good separation of all the peaks. Specificity was demonstrated by the retention characteristics, UV spectra and peak purity index. Linearity, precision, recovery and sensitivity were satisfactory. The procedure was applied to the analysis of tetracycline residues (tetracycline, oxytetracycline (OTC), chlortetracycline (CTC), doxycycline (DC), minocycline (MINO) and methacycline (MTC)) in honey of different types. Extraction involved using a mild acidic solvent containing EDTA to release protein-bound or sugar-bound tetracyclines. For the clean-up step, solid phase extraction using phenyl cartridges was applied. Detection limits in the honey using the proposed procedure are between 15 and 30 ng g(-1), depending on the tetracycline.     

Development and validation of an analytical methodology for the determination of p,p′-DDT, p,p′-DDE and p,p′-DDD in fish oil pills

An analytical methodology was proposed and validated to be applied to the determination of p,p′-DDT and its metabolites p,p′-DDE and p,p′-DDD in fish oil. The analytical procedure presented in this paper involves a single-step clean up process prior to the analysis. A solution of 1,2,3,4-tetrachloronaphtalene was used as internal standard.The analytical technique used was gas chromatography coupled to an electron capture detector. Details on the validation process are provided.The limits of detection ranged from 2.6 to 4.7 pg μL^− 1. The BCR 598 standard reference material (cod liver oil) was used to evaluate the performance of the methodology with satisfactory recoveries for all the compounds.The analytes were determined in three different fish oil pills sold in Spain as a supplementary vitamin support. The sum of p,p′-DDT and metabolites was from 13.2 to 51.3 ng g^− 1, the dominant compound being p,p′-DDE.     

Characterization of three agave species by gas chromatography and solid-phase microextraction-gas chromatography-mass spectrometry

Steam distillation (SD) extraction-solid-phase microextraction coupled to GC-MS was developed for the determination of terpenes and Bligh-Dyer extraction-derivatization coupled with GC for the determination of fatty acids such as ethyl esters were used. It was found that the three different Agave species have the same profile of fatty acids; the quantity of these compounds is different in each Agave variety. On the other hand, different terpenes were identified in the three Agave plants studied: nine in A. salmiana, eight in A. angustifolia and 32 in A. tequilana Weber var. azul.     

Synthesis, characterization, and tautomerism of four novel copper(I) complexes from 3-hydroxy-3-(p-R-phenyl)-2-propenedithioic acids

The paper describes the synthesis and structural characterization of four novel copper(I) complexes [CuL(PPh(3))(2)] (L = 3-hydroxy-3-(p-R-phenyl)-2-propenedithioate). In addition, a tautomeric equilibrium in solution was found and Hammett correlations with (13)C NMR parameters were studied. The structure of one complex was fully established by X-ray diffraction analysis.