The assessment of analytical double-shot pyrolysis with gas chromatograph-mass spectrometry application opportunity for the humic matter investigation in situ

Double-shot pyrolysis with gas chromatography and mass detection (Double-shot GC MS) was conducted for a sample of typical chernozem and humic acids separated from it. The humic acids preparations were pyrolyzed at 500, 600 and 700°C. The data were compared with the lignin pyrograms witch were obtained under similar conditions. It was shown that 500°C is the optimum temperature for pyrolysis of humic acids obtained from Chernozems. Toluene in pyrolysis products may be considered as a marker of excessively high temperature occurring during the experiment. The results of a Double-shot pyrolysis for the soil itself and the humic acids which were extracted from it were compared. Eight products of the soil pyrolysis coincided with substances determined in humic acids (with a total of 41). In the case of thermal desorption of the soil, there were only three such substances, and they also were detected during subsequent pyrolysis of the soil sample. The data obtained speak about the predominantly macromolecular composition of humic substances. The conducted works demonstrate the posibility and perspective for using the Double-shot pyrolysis GC MS for in situ investigation of soil organic matter, humus matter in general and humic acids in particular.