PYROLYSIS MASS-SPECTROMETRY OF WHOLE SOILS, SOIL PARTICLE-SIZE FRACTIONS, LITTER MATERIALS AND HUMIC SUBSTANCES - STATISTICAL EVALUATION OF SAMPLE WEIGHT, RESIDUE, VOLATILIZED MATTER AND TOTAL ION INTENSITY

Abstract

A set of 115 samples with known organic carbon (C(org)) concentrations, divided in the sample groups whole soils (n = 39), soil particle-size fractions (n = 33) and litter materials and humic substances (n = 43), was investigated repeatedly (3-6 replicates) by pyrolysis-mass spectrometry using field ionization as a soft ionization mode (Py-FIMS). Statistical evaluation of the results supplied basic information on the reproducibility of Py-FIMS measurements of these complex organic materials, as well as on the influence of C(org) concentration on volatilization and total ion intensity (TII). The relative error in measurement for sample weight amounted to 10 %, for percentage of residue to 2 %, for percentage of volatilized matter to 5 % and both for TII/mg sample and TII/mg C(org) to 17 %. The relative errors in measurement of sample weight, TII/mg sample and TII/mg C(org) of the total sample set corresponded with those of each group, however differences were observed for the percentages of residue and volatilized matter. Linear correlation and regression analyses show that larger C(org) concentrations result in a significant increase in percentage of volatilized matter and TII/mg sample, whereas percentages of residue were significantly decreased. On the average of all samples, 75.2 % of the variation of TII/mg sample was due to C(org) concentration and the percentage of volatilized matter. For the total sample set covering a wide range of plant and humus materials, the relative error in measurement of TII/mg sample was independent Of C(org) concentration, sample weight, percentage of residue and percentage of volatilized matter.