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1997 (1)
1995 (1)
1Author    Takao Oi, Hirotsugu Takeuchi, Akiko Sakurai, Yoshifumi Taguchi, Morikazu HosoeRequires cookie*
 Title    Boron Isotope Effect in Liquid Chromatography with Boron-specific Resins as Packing Material  
 Abstract    Boron isotope separation by liquid chromatography using boron specific resins with N-methyl glucamine as the functional group was performed. The single-stage separation factor, S, is generally dependent on the resin in the sequence S (free base form resin) > S (F~ form resin) >5 (CP form resin) ^S (Br ~ form resin) for given experimental conditions. This sequence is the same as that of the pH value expected in the resin phase and reasonably understandable by assuming in addition to the predominant four-coordinate species a three-coordinate boron species in the resin phase whose relative abundance increases with decreasing pH. Supporting evidence for three-coordinate species was obtained by 1: B NMR measurements of boric acid-glycerol and boric acid-l,3-propane-diol solutions. 
  Reference    Z. Naturforsch. 52a, 821—827 (1997); received May 23 1997 
  Published    1997 
  Keywords    Boron isotopes, isotope separation, boron specific resin, liquid chromatography, "BNMR 
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 TEI-XML for    default:Reihe_A/52/ZNA-1997-52a-0821.pdf 
 Identifier    ZNA-1997-52a-0821 
 Volume    52 
2Author    Reinhold Tacke3, Dirk Reichel3, KurtG. Ünther5, StefanM. ErgetbRequires cookie*
 Title    The First Liquid-Chromatographic Separation of the (/?)-and (S)-Enantiomers of a Chiral Silanol, Silane and Germane  
 Abstract    The racemic mixtures of the muscarinic antagonists cyclohexyl(phenyl)(2-pyrrolidino-ethyl)silanol (sila-procyclidine, rac-1), cyclohexyl(hydroxymethyl)phenyl(2-piperidinoethyl)-silane (rac-2) and cyclohexyl(hydroxymethyl)phenyl(2-piperidinoethyl)germane (rac-3) were resolved by analytical liquid chromatography (H PLC) using chemically modified cellulose (1) or amylose (2, 3) as the chiral stationary phase. This chromatographic method was used for the quantitative determination of enantiomeric purity of the (R)-and (S)-enantiomers of 1 -3 , which were obtained by preparative resolution with chiral auxiliary agents. Further­ more, the enantiomeric purity o f these samples was established by 13C NM R studies using chiral shift reagents. According to these studies, the resolved antipodes of 1 -3 (obtained by preparative resolution) were almost enantiomerically pure [HPLC: >98.2% ee ((R)-3) to 99.4% ee ((tf)-l, (S)-l); NMR: > 97% ee]. 
  Reference    Z. Naturforsch. 50b, 568 (1995); received October 31 1994 
  Published    1995 
  Keywords    Chiral Silanol, Chiral Silane, Chiral Germane, Liquid Chromatography, Separation o f Enantiomers 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-0568.pdf 
 Identifier    ZNB-1995-50b-0568 
 Volume    50