AN ECONOMICAL METHOD FOR THE PREPARATION OF PLANT AND ANIMAL TISSUE FOR DELTA-C-13 ANALYSIS

This study describes an economical and simple apparatus and methodology for preparing plant material for delta-C-13 analysis by the combustion of material in sealed Pyrex tubes at 550-degrees-C. The largest difference in delta-C-13 for samples combusted at 550-degrees-C in Pyrex tubes compared with those combusted at 800-degrees-C in the more expensive Vycor tubes was 0.65 delta units. Pyrex combustion tubes are approximately 7% of the cost of Vycor tubes and are easier to handle. Excellent reproducibility was observed with an average standard deviation for samples combusted at 550-degrees-C and 800-degrees-C of 0.12 and 0.13 units of delta-C-13, respectively. During the cryogenic distillation of CO2 from the other gasses generated during the combustion, equilibration and evacuation times were varied between 10 s and 120 s. Sample size was varied between 0.4 mg and 2.2 mg. Variations in evacuation time, equilibrium time, and sample size did not significantly affect the value for delta-C-13. The total duration for the cryogenic distillation of one sample was approximately 5 min.