10.1371/journal.pone.0189653
Patrycja Boguta
Patrycja
Boguta
Zofia Sokołowska
Zofia
Sokołowska
Kamil Skic
Kamil
Skic
Use of thermal analysis coupled with differential scanning calorimetry, quadrupole mass spectrometry and infrared spectroscopy (TG-DSC-QMS-FTIR) to monitor chemical properties and thermal stability of fulvic and humic acids
Public Library of Science
2017
humic
weight loss
stability
TG-DSC-QMS-FTIR
N 2 pyrolytic atmosphere
chemical properties
COOH
DSC
FTIR
temperature intervals
scanning calorimetry
FA
quadrupole mass spectrometry
QMS
R 3. Variability
sample
HA
TG
TD
2017-12-14 18:41:51
Dataset
https://plos.figshare.com/articles/dataset/Use_of_thermal_analysis_coupled_with_differential_scanning_calorimetry_quadrupole_mass_spectrometry_and_infrared_spectroscopy_TG-DSC-QMS-FTIR_to_monitor_chemical_properties_and_thermal_stability_of_fulvic_and_humic_acids/5704504
<div><p>Thermogravimetry–coupled with differential scanning calorimetry, quadrupole mass spectrometry, and Fourier-transform infrared spectroscopy (TG-DSC-QMS-FTIR)–was applied to monitor the thermal stability (in an N<sub>2</sub> pyrolytic atmosphere) and chemical properties of natural polymers, fulvic (FA) and humic acids (HA), isolated from chemically different soils. Three temperature ranges, R1, 40–220°C; R2, 220–430°C; and R3, 430–650°C, were distinguished from the DSC data, related to the main thermal processes of different structures (including transformations without weight loss). Weight loss (ΔM) estimated from TG curves at the above temperature intervals revealed distinct differences within the samples in the content of physically adsorbed water (at R1), volatile and labile functional groups (at R2) as well as recalcitrant and refractory structures (at R3). QMS and FTIR modules enabled the chemical identification (by masses and by functional groups, respectively) of gaseous species evolved during thermal decomposition at R1, R2 and R3. Variability in shape, area and temperature of TG, DSC, QMS and FTIR peaks revealed differences in thermal stability and chemical structure of the samples between the FAs and HAs fractions of different origin. The statistical analysis showed that the parameters calculated from QMS (areas of m/z = 16, 17, 18, 44), DSC (Max<sub>DSC</sub>) and TG (ΔM) at R1, R2 and R3 correlated with selected chemical properties of the samples, such as N, O and COOH content as well as E2/E6 and E2/E4 indexes. This indicated a high potential for the coupled method to monitor the chemical changes of humic substances. A new humification parameter, H<sub>TD</sub>, based on simple calculations of weight loss at specific temperature intervals proved to be a good alternative to indexes obtained from other methods. The above findings showed that the TG-DSC-QMS-FTIR coupled technique can represent a useful tool for the comprehensive assessment of FAs and HAs properties related to their various origin.</p></div>