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41.
N. C. van de Merbel M. Stenberg R. Öste G. Marko-Varga L. Gorton H. Lingeman U. A. Th. Brinkman 《Chromatographia》1995,41(1-2):6-14
Summary A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citratesodium chloride buffer. Enantioseparation is by subsequent injection of 3 l heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity. 相似文献
42.
The 1,10-phenanthroline (phen) complexes of Co(II), Ni(II), Cu(II) and
Cd(II) orotates were synthesized and characterized by elemental analysis,
magnetic susceptibility, spectral methods (UV-vis and FTIR) and thermal analysis
techniques (TG, DTG and DTA). The Co(II), Ni(II), Cu(II) and Cd(II) ions in
diaquabis(1,10-phenanthroline)metal(II) diorotate octahedral complexes [M(H2O)2(phen)2](H2Or)2·nH2O
(M=Co(II), n=2.25; Ni(II), n=3;
Cu(II) and Cd(II), n=2) are coordinated
by two aqua ligands and two moles of phen molecules as chelating ligands through
their two nitrogen atoms. The monoanionic orotate behaves as a counter ion
in the complexes. On the basis of the first DTGmax,
the thermal stability of the hydrated complexes follows the order: Cd(II),
68°C 68°C 相似文献
43.
Trimethylsilyl Cyanide — A Reagent for Umpolung, VI. Anionic 1,4-O→C-Silyl Group Rearrangement The adducts 6 from substituted acroleins 5a – f and trimethylsilyl cyanide form the anions 6 A on deprotonation at −78°C, which are silylated by trimethylsilyl chloride to 7 or (and) 8 in positions 3 or (and) 1. On warming up to room temperature, 6a A and 6b A undergo smoothly 1,4-O→C-silyl group rearrangements to form 13a A and 13b A which can be trapped by silylation. 6c – d A decompose on warming up. Triethylsilyl instead of trimethylsilyl groups decelerate the rearrangement appreciably. Structure and configuration of the different products are determined. 相似文献
44.
Investigation of potential-sensitive fluorescent dyes for application in nitrate sensitive polymer membranes 总被引:2,自引:0,他引:2
Gerhard J. Mohr Frank Lehmann Ralf Östereich Ivana Murkovic Otto S. Wolfbeis 《Analytical and bioanalytical chemistry》1997,357(3):284-291
The applicability of various potential-sensitive dyes (PSD) for optical sensing of anions is reported. Specifically, nitrate-responsive
polymer membranes have been developed which are composed of a plasticized polymer, an anion exchange catalyst, and a fluorescent
dye. On exposure to nitrate, the fluorescence intensity of such membranes increases, while the wavelengths of the excitation
and emission maxima remain virtually unchanged. The membranes typically are 2–4 μm thick and exhibit highest sensitivity to
nitrate in the 2 to 200 mgl–1 range. Signal changes on exposure to 100 mmol/l nitrate can be as high as +300%. The detection limit is 0.2 mgl–1. The cationic PSD octadecyl acridine organe was tested in combination with a tin-organic and an indium-organic anion carrier
rather than with tridodecylmethylammonium chloride, but both carriers were found to display no improved selectivity.
Received: 2 December 1995 / Revised: 28 March 1996 / Accepted: 5 April 1996 相似文献
45.
The protonation constants of two nitro-Schiff bases SB1, SB2 and three asymmetric tetradentate diimines H2L1, H2L2 and H2L3 and the stability constants of their ML type binuclear Ni(II) and Fe(III) complexes have been determined potentiometrically. The asymmetric diimines are (2OH) RCHNC6H4CHNR′ (2OH) type compounds [where R = R′ = phenyl for H2L1; R = naphthyl, R′ = phenyl for H2L2 and R = R′ = naphthyl for H2L3]. The effect of tautomeric forms on the acid-base properties of the diimines has been investigated and discussed. In addition, dimeric and binuclear Ni(II) and Fe(III) complexes of the diimines have been synthesized and characterized by physical and spectroscopic techniques. Also, in vitro antimicrobial activities of the diimines and the complexes have been evaluated against three bacteria: Micrococcus luteus (NRLL B-4375), Bacillus cereus (RSKK 863), Escherichia coli (ATCC 11230) and the fungus: Candida albicans (ATCC 10239). 相似文献
46.
N. Öztürk T. Akyüz A. Y. Erkol 《Journal of Radioanalytical and Nuclear Chemistry》1995,201(5):439-446
The Eskiehir-Beylikahir district has the largest and richest thorium and rare earth elements deposits in Turkey. The uranium and thorium concentrations of samples taken from four different parts of this area have been determined by the delayed neutron counting technique. The results are compared with those of previous analyses by other techniques and found to be in good agreement. 相似文献
47.
4,4-Bis(chloroacetyl)diphenylmethane has been prepared from ClCH2COCl and Ph2CH2. 4,4-Methylenebis(phenylglyoxylohydroximoyl chloride has also been obtained. Four new substituted 4,4-bis(alkylaminoisonitrosoacetyl)diphenylmethanes (ligands) have been prepared from 4,4-methylenebis(phenylglyoxylohydroximoyl chloride) and the corresponding amines. The NiII, CuII and CoII complexes of these ligands were prepared and their structures were identified using AAS, i.r., 1H-n.m.r. spectral data, elemental analyses and magnetic susceptibility measurements. 相似文献
48.
Cabergoline (CAB) is an ergot alkaloid derivative with dopamine agonist activity. A novel, simple, and rapid stability-indicating high-performance liquid chromatographic (HPLC) method for assay of CAB in tablets has been developed and validated. Chromatography was performed on a 4.6 mm i.d. × 250 mm, 5 μm particle, cyano column with acetonitrile–10 mM phosphoric acid, 35:65 (v/v), containing 0.04% triethylamine, as mobile phase, at a flow rate of 1.0 mL min?1, and UV detection at 280 nm. Response was a linear function of concentration in the range 0.1–4 μg mL?1 (r 2 = 0.9999). The recovery of the method was good (99.45%) and RSD values for intra-day and inter-day precision were 0.24–0.88% and 0.66–1.19%, respectively. The method can be used for quality-control assay of CAB in tablets, for stability studies, and for in vitro dissolution studies. 相似文献
49.
Österberg M 《Journal of colloid and interface science》2000,229(2):620-627
The effect of a cationic polyelectrolyte, PCMA, on the forces between two cellulose surfaces and between one cellulose surface and one mica surface has been studied using the interferometric surface force apparatus (SFA). The cellulose surfaces were prepared by Langmuir-Blodgett deposition of trimethylsilyl cellulose onto hydrophobized mica. Prior to measurements the surfaces were desilylated to obtain pure cellulose. Introduction of a cationic polyelectrolyte into the solution drastically changed the interactions between the cellulose layers. It was found that the cationic polyelectrolyte does adsorb onto the cellulose surface, although the adsorbed amount is low. The adsorbed layer is very thin, as expected at a low electrolyte concentration. Before the adsorption has reached equilibrium, when only some polyelectrolyte had adsorbed, the adhesion between the surfaces was high, and it was noted that the cellulose layer was damaged on separation. After a longer adsorption time an electrostatic repulsion and no adhesion were observed between the polyelectrolyte-coated cellulose surfaces. An electrostatic repulsion was observed between cellulose and mica. When cationic polyelectrolyte was introduced to the system it overcompensated the charges on both surfaces, and the range and magnitude of the double-layer force was higher than without polyelectrolyte. The relevance of the results to flocculation mechanism and efficiency in cellulose systems is discussed. Copyright 2000 Academic Press. 相似文献
50.
Reactions with Organophosphorus Compounds, 49. Synthesis and 1H NMR Spectra of (3-Acylbicyclo[2.2.1]hept-5-en-2-yl)phosphonates Reaction of the (E)-(β-acylvinyl)phosphonates 1 with cyclopentadiene yields the isomeric norbornylphosphonates 2 (endo-acyl, exo-P) and 3 (exo-acyl, endo-P) in a 7:3 ratio. With 1,3-cyclohexadiene the corresponding bicyclooctenyl derivatives 7 and 8 are obtained from 1a . The (Z)-phosphinylacrylate 4 gives with cyclopentadiene the isomers 5 (exo-CO2Me, exo-P) and 6 (endo-CO2Me, endo-P) in nearly equal amounts. The configuration of the cycloadducts has been proved by 1H NMR spectroscopy. 相似文献