Hi Tim, From a carbohydrate chemistry point of view, I'm afraid the answer is yes. If one dissolves sucrose (= saccharose, a disaccharide) in water, sucrose will start to become hydrolysed into D-glucose (C6H12O6) and D-fructose (C6H2O6). This reaction consumes one mol equivalent of water per mol equivalent sucrose (C12H22O11), so the 18O composition of the product will change and the degree of this change will depend how much of the sucrose was hydrolysed before the reaction was stopped. Before anybody says it, I know this reaction is pH dependent, i.e. the reaction rate is directly proportional to the H+ concentration; but it will take place even in 'pure' water albeit slow. One can follow the reaction quite easily with a polarimeter as the polarisation angle of the (pure sucrose) solution (+65°) becomes smaller and smaller and eventually (at equilibrium) ends up being -20°. While on this subject, again for reasons of sugar chemistry, I would be cautious even when it comes to monosaccharides such as D-glucose since glucose dissolved in water undergoes a change from alpha- to beta-glucose involving an opening of the ring at the acetal-O between C5 and C1. On paper, this step does require a "helper" molecule of water but I don't think anybody has ever looked at this by e.g. dissolving D-glucose in 18O-labelled water. Best regards, Wolfram On Jul 20 2005, Heaton, Timothy HE wrote: > Can sucrose undergo O-isotope exchange with water? In preliminary tests > we are finding slight differences in d18O between IAEA CH-6 weighed out > into capsules as a solid powder, and the same IAEA CH-6 dissolved in > water and pipetted into capsules. All cases used well-homogenised powder > and thorough freeze-drying. > > Tim H.E. Heaton > > NERC Isotope Geosciences Laboratory > British Geological Survey > Keyworth, Nottingham NG12 5GG, England > (www.bgs.ac.uk/nigl/index.htm) > > Tel. +44(0)115 936 3401 > Email: [log in to unmask] > > > ********************************************************************* > This e-mail message, and any files transmitted with it, are confidential > and intended solely for the use of the addressee. However, the > information contained in this e-mail may subsequently be subject to > public disclosure under the Freedom of Information Act 2000 and, unless > the information is legally exempt from disclosure, the confidentiality of > this e-mail and your reply cannot be guaranteed. If this message was not > addressed to you, you have received it in error and any copying, > distribution or other use of any part of it is strictly prohibited. Any > views or opinions presented are solely those of the sender and do not > necessarily represent those of the British Geological Survey. The > security of e-mail communication cannot be guaranteed and the BGS accepts > no liability for claims arising as a result of the use of this medium to > transmit messages from or to the BGS. http://www.bgs.ac.uk > *********************************************************************