This report summarizes the ways and means by which /sup 13/Co/sub 2/ production procedure from organic matter can be standardized. Optimum sample preparation conditions were determined to get reproducible results. Plant combustion for six minutes at 900-1000 degree C with pure O/sub 2/ and ten minutes for conversion of CO to CO/ sub 2/ over CUO gauze at 850 degree C have been found optimum conditions. Internal standards: PINSTECH wheat straw, PINSTECH grass sample, Glucose-D glaxo PINSTECH and polyethylene foil PINSTECH were selected, and calibrated against IAEA Sucrose and polyethylene foil standards. These internal standards have been used for correction of delta 13 C results. The mechanisms for the correction of results has been described. Causes of isotope fractionation of plant samples were determined. Statistical summary of measured results for delta /sup 13/C standards has also been given. (author).