Simplified high-performance liquid chromatographic determination of residual amprolium in edible chicken tissues

A simplified determining method for the routine monitoring of residual amprolium in edible chicken tissues (muscle and liver) is developed using a high-performance liquid chromatographic (HPLC) method with a photodiode-array detector after sample cleanup by an Ultrafree-MC/PL centrifugal ultrafiltration unit. For the HPLC determination and identification, a Mightysil RP4 GP column and a mobile phase of an ethanol-5 mM 1-heptanesulfonic acid sodium salt solution (35:65, v/v) using an ion-pairing system with a photodiode-array detector are used. Average recoveries (spiked at 0.3-3.0 microg/g) are > 90%. The inter- and intravariabilities are 1.9-2.4%. The limits of quantitation are 0.22 microg/g for muscle and 0.25 microg/g for liver. The total time and solvent required for the analysis of one sample are < 20 min and < 2 mL of ethanol, respectively. No toxic solvents and regents are used.     

Simplified high-performance liquid chromatographic determination of residual amprolium in edible chicken tissues

A simplified determining method for the routine monitoring of residual amprolium in edible chicken tissues (muscle and liver) is developed using a high-performance liquid chromatographic (HPLC) method with a photodiode-array detector after sample cleanup by an Ultrafree-MC/PL centrifugal ultrafiltration unit. For the HPLC determination and identification, a Mightysil RP-4 GP column and a mobile phase of an ethanol-5 mM 1-heptanesulfonic acid sodium salt solution (35:65, v/v) using an ion-pairing system with a photodiode-array detector are used. Average recoveries (spiked at 0.3-3.0 microg/g) are > 90%. The inter- and intravariabilities are 1.9-2.4%. The limits of quantitation are 0.22 microg/g for muscle and 0.25 microg/g for liver. The total time and solvent required for the analysis of one sample are < 20 min and < 2 mL of ethanol, respectively. No toxic solvents and regents are used.     

Flow-injection determination of 9,10-phenanthrenequinone with catalytic photometric detection

A catalytic photometric method with a flow-injection system is described for the determination of 9,10-phenanthrenequinone. It is based on the catalytic effect of 9,10-phenanthrenequinone on the redox reaction of 1,2-dinitrobenzene with formaldehyde under alkaline conditions. 9,10-Phenanthrenequinone at the 5.0 x 10(-8)-5.0 x 10(-6)M level can be determined at a rate of 20 samples/hr. The detection limit is 1.0 x 10(-8)M (40 pg in a 10-microl injection).     

Development of a high-performance liquid chromatographic system with enzyme reactors for the determination of N-acetyl branched-chain amino acids

Immobilized enzymes were used as column reactors in a high-performance liquid chromatographic system for the specific detection of N-acetyl branched-chain amino acids (AcBCAs) such as N- acetyl- l -valine (AcVal), N- acetyl- l -leucine (AcLeu) and N- acetyl- l -isoleucine (AcIle). Aminoacylase and leucine dehydrogenase were immobilized onto poly(vinyl alcohol) beads. The AcBCAs were separated as three peaks on a Capcell C(1) SG120 column with 0.03M phosphate buffer (pH 8.0). Aminoacylase was capable of hydrolysing the AcBCAs to amino acids, which react with beta-nicotinamide adenine dinucleotide (NAD(+)) in the presence of leucine dehydrogenase. The reduced nicotinamide adenine dinucleotide (NADH) produced was monitored fluorimetrically. The calibration graphs were linear from 4 to 200muM for AcVal and AcLeu, and from 5 to 300muM for AcIle; detection limits for AcVal, AcLeu and AcIle were 2, 2 and 3muM, respectively. The immobilized aminoacylase reactor should be renewed every 5 days owing to a poor stability of aminoacylase.     

Carbonyl methylenation of easily enolizable ketones

An organometallic reagent prepared from CH₂I₂, Zn, and TiCl₄ is effective for methylenation of the title ketones.     

Diversity-oriented synthesis of tamoxifen-type tetrasubstituted olefins

A general synthetic scheme for tamoxifen-type tetrasubstituted olefins based on the novel Cu-catalyzed carbomagnesation across alkynyl(2-pyridyl)silane has been developed. A wide array of electronically and structurally diverse tetrasubstituted olefins can be prepared in a regiocontrolled, stereocontrolled, and diversity-oriented manner. Noteworthy features are that (i) the three aryl groups, which are believed to be important (essential) for anti-estrogenic activity, can be varied at will because they all stem from readily available aryl iodides, and (ii) any stereo- and regioisomers can, in principle, be prepared by simply changing the applying order of aryl iodides into the sequence.     

The cellulose system in viscin from mistletoe berries

The cellulose system of the viscous fibrous cellulosic polysaccharide (viscan) in the viscin tissue of the European mistletoe, Viscum album L., was analyzed by chemical and physicochemical techniques including sugar analysis, optical and transmission electron microscopy, X-ray and electron diffraction together with solid state CP/MAS ¹³C-NMR spectroscopy. The results confirmed that in the elongated thin viscin cells, the cellulose microfibrils (having a diameter of around 3 nm) were tightly coiled with their axes perpendicular to the long axis of the cell. Upon stretching these cells became deformed by more than a hundred fold. In such a deformation, the cellulose microfibrils became unwound to be perfectly aligned along the stretching direction. Based on solid-state CP/MAS ¹³C-NMR spectroscopic analysis of the viscin tissue, it was found that its cellulose consisted of I and I polymorphs in the ratio 1:1.     

Copper-catalyzed allylation of carbonyl derivatives using allyl(2-pyridyl)silanes

[reaction: see text] We have developed an efficient copper-catalyzed allylation of carbonyl derivatives using allyl(2-pyridyl)silanes, in which the strong directing effect of the 2-pyridyl group was observed. A useful synthesis and allylation of substituted allyl(2-pyridyl)silanes is also described.     

Rhodium-catalyzed highly selective thioformylation of acetylenes with thiols and carbon monoxide

Highly regioselective thioformylation of terminal acetylenes with thiols and carbon monoxide has been developed by the use of rhodium(I) complexes as the catalyst: formyl and thio groups are introduced into the terminal and inner positions of acetylenes, respectively. The thioformylation is performed in the presence of a catalytic amount of rhodium(I) complexes, such as RhH(CO)(PPh₃)₃, RhCl(PPh₃)₃, and RhCl(CO)(PPh₃)₂, under the pressure of CO (3 MPa) at 120°C in CH₃CN to provide β-thio-α,β-unsaturated aldehydes in good yields. This thioformylation can be applied to a variety of terminal acetylenes and aromatic thiols. A mechanistic proposal includes the formation of the rhodium sulfide complex as the key species.     

A New Approach to the Construction of BEDT-TTF Derivatives Condensed with Heterocycles via BF3-promoted Reactions of Organotin Thiolates

The synthesis of BEDT-TTF derivatives fused with heterocycles (3–7) has been accomplished via the BF₃-promoted reaction of organotin thiolates (8 and 9) with electrophiles (10 and 11). Electrical conductivities of radical cation salts derived from some of them were also investigated.