Carbon and oxygen isotope working standards from C3and C4photosynthates

A preparation of organic working standards for the online measurement of 13C/12C and 18O/16O ratios in biological material is presented. The organic working standards are simple and inexpensive C3 and C4 carbohydrates (sugars or cellulose) from distinct geographic origin, including white sugar, toilet and XEROX papers from Switzerland, maize from Ivory Coast, cane sugar from Brazil, papyrus from Egypt, and the core of the stem of a Cyperus papyrus plant from Kenya. These photosynthetic products were compared with International Atomic Energy standards CH-3 and CH-6 and other calibration materials. The presented working standards cover a 15 ‰ range of 13C/12C ratios and 9 ‰ for 18O/16O, with a precision 10. Revised version of a paper presented at the VIII Isotope Workshop of the European Society for Isotope Research (ESIR), 25–30 June 2005, Leipzig-Halle, Germany.