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201.
Chromatographia - An LC-MS method is described for the determination of 4,4′-MDA (4,4′-methylene dianiline) in hydrolysed urine as a biomarker for exposure to 4,4′-MDI... 相似文献
202.
Chromatographia - The reversed phase behaviour of high molecular mass polystyrenes was investigated on C18 bonded phase columns with ethyl acetate-methanol and ethyl acetateacetonitrile mobile... 相似文献
203.
Chromatographia - A theoretical model is used to predict retention times of divalent metal cations in single-column ion chromatography using one or more ligands in the eluent. Stability constants... 相似文献
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Separation of 23 dansylated amino acids by micellar electrokinetic chromatography at low temperature
Summary The baseline separation of 23 dansylated amino acids (including 3 didansylated species) is reported. Lowering of the analysis
temperature and fine control of the surfactant concentration were essential in obtaining this result. Calibration graphs with
good linearity were obtained. 相似文献
209.
Twelve series of linear oligomers of four different degrees of polymerization (xn = 8.77−41.55), having a common perfluorinated random copolymeric chain as molecular body and two equal foreign end units of one of the types listed in Table 1, have been synthesized by derivatization of base samples of one of them having a diolic---CH2OH functionality. The glass transition temperature Tg of all the series was measured and thus examined as a function of xn. A clear end unit effect is observed, dominantly determined in every series by chemical nature and structure of the end units, quantitatively expressed at any xn by different positive or negative Tg deviations from the common asymptotic Tg∞ value. The results are also discussed in terms of copolymer end effect and of relation between Tg and end copolymeric composition. 相似文献
210.
Synthesis of optically active sesquiterpenes with a eudesmane C-skeleton from the chiral starting material thujone involves transformation of a tricyclic intermediate (1R,2R,4S)-1,7-dimethyl-4-(1-methylethyl)tricyclo[4.4.0.02,4]dec-6-en-8-one ( 2 ) into the bicyclic compound β -cyperone ( 5 ). Hydroxylation of 2 at C(5) or C(11) permits subsequent opening of the cyclopropane ring and rearrangement to β -cyperone. In this publication, studies involving hydroxylation of 2 by fungal cultures are presented. The resultant products are useful intermediates in efficient synthesis of eudesmane sesquiterpenes. Of five fungi tested, Rhizopus oryzae ATCC 11145 proved most versatile. It hydroxylates at the exocyclic C(11) position in high yield (70%) and, to a lesser extent, at C(5) (5%). Enzymatic activity appears at the end of growth phase and at least 2.2 g of 2 per liter can be metabolized without significant loss of product yield. A second fungus, Cunninghamella echinulata ATCC 9244, proved most useful for hydroxylation of derivatives of 2 for the preparation of derivatives of β -cyperone, although product yields were low (2–20%), some derivatives were nonreactive, and hydroxylation at C(9) occurred. The relationship between precursor structure and enzyme affinity is discussed. 相似文献