Static combustion of biological samples sealed in glass tubes as a preparation for δ13C determination

摘要: The variations in the preparation of biological samples (mainly tropical grasses and legumes) by a modified Dumas combustion method were studied to investigate their effect on reproducibility precision estimating δ13C levels. variables included plant species, evacuation tubes, temperature, amount form (i.e., particle size) oxygen donor, type catalyst mixing ingredients tube.The tubes prior sealing use 2.0 g copper(II) oxide (CuO)(compared with smaller amounts) contributed more improving over-all than any other factor. CuO also led complete some samples. For pasture extrusa from fistulated cattle, there was little choose between two temperatures 550 850 °C). However, for faeces hair samples, at °C resulted positive shift values marked decrease compared results °C. Possible reasons this are discussed. Significant interactions temperature occurred, but magnitude these effects small.On basis obtained, preferred dried ground fine powder (Tema mill), 4–8 mg sample, 2 microanalytical reagent-grade wire-form 3 cm 0.2 mm diameter silver wire 228 long, standard wall, 6 o.d. Vycor tube evacuated 30 × 10–3 Torr sealed an H2– O2 flame. thoroughly mixed shaking, combusted h allowed cool room before being removed furnace. Storage 11 months had no values.The total time 40 using recommended procedure approximately 7 analytical mass spectrometer 12 ± min per sample. error mean three 0.065‰ confidence interval, 95% level probability, 0.057–0.076‰. These lower those published dynamic method.