Dear all We have been running D/H for the first time in several years using a 5 year old batch of Indiana zinc that has been stored in an evacuated flask. H conversion yields seem fine but D/H ratios correlate with sample size (20 permil shift from 0.5 to 5 microlitres). All the obvious remedies have now been tried and I am forced into suspecting the zinc. Does anyone had a similar experienc using old zinc? Can/should it be pretreated/regenerated in any way after languishing for so long? Thanks and best wishes Dave Dave Mattey Geology Dept, Royal Holloway College, University of London, Egham Hill, Egham, Surrey, TW20 0EX Tel: 01784 443587 Office 443582 Secretary 443637 Prism lab 443629 Optima lab 471780 FAX