ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 11, pp. 1957–1962. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © V.D. Tikhova, V.P. Fadeeva, M.I. Dergacheva, M.M. Shakirov, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81,
No. 11, pp. 1841–1846.
Analysis of Humic Acids from Various Soils
Using Acid Hydrolysis
V. D. Tikhova, V. P. Fadeeva, M. I. Dergacheva, and M. M. Shakirov
Vorozhtsov Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Institute of Soil Science and Agrochemistry, Siberian Branch, Russian Academy of Sciences,
Received April 23, 2008
Abstract—Structural changes in humic acids from various soils, produced by acid hydrolysis, are studied by
elemental and thermal analyses and by IR and NMR spectroscopy.
According to the modern views of the structure of a
humic acid (HA) macromolecule, it consists of two
major parts, a core built by aromatic fragments inter-
linked by aliphatic chains and a periphery consisting of
readily hydrolyzable oxygen-containing fragments
such as polysaccharides, ethers, polyphenols, and
amino acids. Orlov  noted that the terms
“periphery” and “core” are not quite adequate and that
it would be more correct to designate these parts as
hydrolyzable and nonhydrolyzable, which, however,
appears to be inconvenient, and no adequate alternative
for the above-mentioned terms has been found yet.
The use of hydrolytic methods for analysis of HAs
originates from routine procedures employed for
analysis of complex protein molecules. However, in
contrast to proteins, none of HAs ever extracted have
been fully decomposed via hydrolysis. The hydro-
lyzates were intensively studied, including their amino
acid composition [2–10], polysaccharide fraction [11–
15], and other components [10, 15].
The goals of this study were to examine the
changes in the composition and structure of HAs, pro-
duced by acid hydrolysis, and to compare nonhydro-
lyzable fractions of HAs from soils of different gene-
sis, using such methods as elemental and thermal
analyses, IR, and NMR.
(sample no. 1) and surface-gley clay loam (sample no.
2)] and dry-steppe zone of the Altai krai [warm soils:
southern chernozem (sample no. 3) and chestnut soil
(sample no. 4)].
The experiments on acid hydrolysis of HAs were
carried out as follows . A weighed portion (about
100 mg) of a sample was heated in a specially de-
signed flask with 2.5 ml of 6 M HCl for 18 h at 120°C
(sand bath) under helium. The residue was filtered off,
washed with distilled water to remove the chloride
ions, and air-dried to constant weight.
Carbon, hydrogen, and nitrogen were determined
on a Carlo Erba Model 1106 elemental analyzer and
also using the standard C,H analysis procedure for or-
To measure NMR spectra, a 20–50-mg sample was
dissolved in 0.5 ml of NaOH/D
O and placed into an
ampule with an outer diameter of 5 mm. The
spectra were recorded on a Bruker DRX-500 instru-
ment operating at 125.76 MHz. To exclude the nuclear
Overhauser effect, the
C NMR spectra were recorded
with proton decoupling in the INVGATE mode.
Tetramethylsilane (TMS) was used as external refer-
ence. The spectra were recorded at 1-s pulse delay.
The IR spectra were recorded over the range 400–
on a Vector-22 FTIR spectrometer (Bruker)
using KBr technique (1:150).
AND INDUSTRIAL ORGANIC CHEMISTRY
We studied HAs extracted from tundra soils of the
Tyumen oblast [cold soils: gley podzolic sandy loam
Thermal analysis was carried out on an STA 409
PC Luxx thermoanalyzer (Netzsch) in a platinum cru-