A preparation of organic working standards for the online measurement of
C-13/C-12 and O-18/O-16 ratios in biological material is presented. The
organic working standards are simple and inexpensive C-3 and C-4
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 parts per thousand range of C-13/C-12
ratios and 9 parts per thousand for O-18/O-16, with a precision < +/-
0.2 parts per thousand for n > 10.