Cyanobacteria, commonly called "blue-green algae", may accumulate in surface water supplies as "blooms" and may concentrate on the surface as blue-green "scums". Some species of cyanobacteria produce toxins and are of relevance to water supplies and to microalgae dietary supplements. To ensure the safety of drinking water and blue-green algae products, analyses are the only way to determine the presence or absence of toxins. This paper shows the use of ultra performance liquid chromatography (UPLC) coupled to orthogonal acceleration time of flight (TOF) mass spectrometry for the detection and quantitation of microcystins. The method presented is very sensitive, simple, fast, robust and did not require fastidious clean-up step. Limits of detection of 0.1 microg L(-1) in water and 0.1-0.2 microg g(-1) in microalgae samples were achieved. Method performances were satisfactory and appropriate for monitoring of water and dietary supplements. The method was applied in routine to samples taken from Swiss market or buy on internet website. Among 19 samples, six showed the presence of microcystins LR and LA at harmful levels. 相似文献
A series of six benzoxazolinone aminoketones and height aminoalcohols has been synthetized as agonist and antagonist ligands for adrenergic receptors. For those benzoxazolinone derivatives which contain one or two chiral carbons, a stereoselective liquid chromatographic method, using silica-based cellulose tris-3,5-dimethylphenylcarbamate (Chiralcel OD-H) or tris-4-methylbenzoate (Chiralcel OJ) as chiral stationary phase, has been developed. A better separation was achieved on cellulose carbamate phase compared to the cellulose ester phase. The effects of concentration of various aliphatic alcohols in the mobile phase were studied. The effects of structural features of the solutes on the discrimination between the enantiomers were examined.
A new route to alpha-keto acids is described, based on the ozonolysis of enol acetates obtained from alpha-substituted beta-keto esters. Escherichia coli branched chain aminotransferase (BCAT) activity toward a variety of substituted 2-oxoglutaric acids was demonstrated analytically. BCAT was shown to have a broad substrate spectrum, complementary to that of aspartate aminotransferase, and to offer access to a variety of glutamic acid analogues. The usefulness of BCAT was demonstrated through the synthesis of several 3- and 4-substituted derivatives. 相似文献
A new family of functionalized ligands derived from norborn-5-ene-2,3-dicarboxylic anhydride has been used in Suzuki C-C cross-couplings between aryl boronic acids and aryl bromide derivatives in [BMI][PF(6)] (BMI=1-n-butyl-3-methyl-imidazolium), using palladium acetate as catalytic precursor. High conversions and yields are obtained when amine ligands containing hydroxy groups are involved. TEM analyses after catalysis show the formation of small nanoparticles, in contrast to the agglomerates observed when nanoparticles are intentionally preformed, with a consequent decrease in the catalytic activity in the latter case. Some tests, including the correlation effect between solvent and ligand, are carried out to try to identify the true nature of the catalyst. All the results obtained suggest that formation of nanoparticles is required to lead to a catalytically active system. 相似文献
NMR and MS analysis as a function of time has shown that the self-assembly of a linear ligand with Fe2+ or Ni2+, metal ions of octahedral coordination geometry, generates first a triple helicate and thereafter the circular helicate 1 as kinetic and thermodynamic products, respectively. The results provide insight into features of the energy hypersurface on which this self-assembly operates and point to the general role of kinetic and thermodynamic control in such processes. 相似文献
Baseline separation of 18 new substituted benzimidazole derivatives, potent AMP‐activated protein kinase (AMPK) activators, with one chiral center, was achieved by CD‐EKC using sulfated and highly sulfated CDs (SCDs and HS‐CDs) as chiral selectors. The influence of the type and concentration of the chiral selectors on the enantioseparations was investigated. The SCDs exhibit a very high enantioselectivity power since they allow excellent enantiomeric resolutions compared to those obtained with the neutral CDs. The enantiomers were resolved with analysis times around 6 min using 25 mM phosphate buffer at pH 2.5 containing either β‐S‐CD, HS‐β‐CD, HS‐γ‐CD (3 or 4% w/v) at 25°C, with a voltage of 20 kV. The apparent association constants of the inclusion complexes were calculated. The study of the solute structure‐enantioseparation relationships seems to show the high contribution of the interactions between the solutes phenyl ring and the CDs to the enantiorecognition process. The optimized method was briefly validated (LOD less than 1%) and the purity of enantiomers of compound 3 was determined. The enantiomer migration shows reversal order depending on the kind of CD. 相似文献
Ytterbium and lutetium ionic complexes derived from enantiopure substituted (R)-binaphthylamine ligands, of the general formula [Li(THF)n][Ln[(R)-C20H12(NR)2]2], have been investigated for the hydroamination/cyclization of several aminopentenes and an aminohexene. Complexes with isopropyl or cyclohexyl substituents on nitrogen atoms were found to be efficient catalysts under mild conditions for the formation of N-containing heterocycles with enantiomeric excesses up to 78%. 相似文献