Degradation of complexons derived from succinic acid under UV radiation

Article abstract of DOI:10.1134/S1070427217040024

The destruction of complexons derived from succinic acid under the action of UV radiation was studied. IR spectroscopy, thin-layer paper chromatography, and complexometric titration were used to determine the destruction products of these complexons. It was found that the complexons decompose under UV irradiation substantially more easily than ethylenediaminetetraacetic acid does, and the products of their decomposition can undergo a biological utilization under natural conditions. The data obtained in the study make it possible to choose, instead of ethylenediaminetetraacetic acid, ligands that will be nearly fully destructible in the light without deteriorating the ecology.

Full text of DOI:10.1134/S1070427217040024

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2017, Vol. 90, No. 4, pp. 507−511. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © T.I. Smirnova, S.D. Khizhnyak, V.M. Nikol’skii, Ya.M. Khalyapina, P.M. Pakhomov, 2017, published in Zhurnal Prikladnoi Khimii, 2017,
Vol. 90, No. 4, pp. 406−411.
PHYSICOCHEMICAL STUDIES
OF SYSTEMS AND PROCESSES
Degradation of Complexons Derived from Succinic Acid
under UV Radiation
T. I. Smirnovaa, S. D. Khizhnyakb*, V. M. Nikol’skiib,
Ya. M. Khalyapinaa, and P. M. Pakhomovb
a Tver State Agricultural Academy, ul. Marshala Vasilevskogo 7, Tver, 170904 Russia
b Tver State University, ul. Zhelyabova 33, Tver, 170100 Russia
e-mail: sveta_khizhnyak@mail.ru
Received March 3, 2017
Abstract—The destruction of complexons derived from succinic acid under the action of UV radiation was
studied. IR spectroscopy, thin-layer paper chromatography, and complexometric titration were used to determine
the destruction products of these complexons. It was found that the complexons decompose under UV irradia-
tion substantially more easily than ethylenediaminetetraacetic acid does, and the products of their decomposition
can undergo a biological utilization under natural conditions. The data obtained in the study make it possible
to choose, instead of ethylenediaminetetraacetic acid, ligands that will be nearly fully destructible in the light
without deteriorating the ecology.
DOI: 10.1134/S1070427217040024
Complexons are widely used in chemical industry,
agriculture, and pharmacy. About 40% of world’s manu-
facture of complexons, which constitutes 200 thousand
tons every year, is represented by ethylenediaminetet-
raacetic acid (EDTA) [1]. The chemical structure of some
complexons is presented in Table 1. About 80% of these
complexons find their way into the environment on being
used [2–4]. Because of the high chemical stability, some
of complexons, e.g., EDTA, are not decomposed under
natural conditions during a long time and accumulate in
the world ocean. Ecologists believe that EDTA is one of
the most widely occurring environmental contaminants
[3].
The goal of our study was to examine the destruction
under UV irradiation of the above organic ligands that
penetrate into the natural medium upon their applica-
tion and to identify substances formed as a result of this
process.
The results obtained will enable an effective choice
of ligands, instead of EDTA, that will nearly fully de-
compose in the light without deteriorating the ecological
equilibrium.
EXPERIMENTAL
We examined the destruction capacity both of com-
plexons derived from succinic acid (IDSA, EDSA,
DCHDSA) via waste-free addition of maleic acid to the
corresponding amino derivatives and of complexons
derived from acetic acid (EDTA, IDAA) at the Research
Institute of Chemical Reagents and Special-Purity
Chemical Substances, with the qualitative composition
of the destruction products determined. The following
auxiliary reagents were used: concentrated nitric acid
and metallic copper for preparing the standard working
Published data on the effect of UV radiation on com-
plexing compounds are scarce [5]. There are single pub-
lications [6] indicating that an insignificant photodestruc-
tion of EDTAoccurs only in the uppermost layers of water
basins. To complexing substances capable of rapidly
decomposing under UV irradiation belong complexons
that are derivatives of succinic acid (CDSAs): iminodis-
uccinic acid (IDSA), ethylenediamiune disuccinic acid
(EDSA), and trans-1,2-diaminocyclohexanedisuccinic
acid (DCHDSA).
507

508
SMIRNOVA et al.
Table 1. Structural formulas of complexons
Complexon
Betainic structure of complexons
Iminodisuccinic acid (IDSA)
Ethylenediaminesuccinic
acid (EDSA)
Diaminocyclohexane
disuccinic acid (DCHDSA)
Ethylwenediaminetetraacetic
acid (EDTA)
Iminodiacetic acid (IDAA)
solution of Cu(NO3)2, butanol-1, glacial acetic acid, ac-
etone, 25% aqueous ammonia, 8-oxyquinoline, indicators
(Nessler reagent, murexide, Bromophenol Blue, ninhy-
drin), amino acids (aspartic acid, asparagine, glycine,
α-alanine, β-alanine), and succinic acid.
EDSA, IDSA, and DCHDSA. Prior to a chromatographic
analysis, the paper was successively treated with a solu-
tion of 8-oxyquinoline in acetone and the mixed solvent.
Chromatograms were developed with a 0.2% solution of
ninhydrin in ethanol and the distribution coefficients Rf
were calculated by the formula
Solutions of EDSA, IDSA, DCHDSA, EDTA, and
IDAAwith concentration of about 10–2 M and volume of
50 mL were placed in Petri dishes and exposed for 1 h to
light from an LUV 15W (ECO (EU) mercury lamp situat-
ed at a distance of 2 cm from the solution surface. Solution
samples (V = 2 mL) upon UV irradiation were analyzed
for ammonium ions with a Nessler reagent. Then, the
residual concentration of the ligands was determined in
the solutions under study by the titrimetric method with
a standard 0.01 M Cu(NO3)2 solution, ammonia buffer
solution, and metallochrome indicator murexide.
li
Rf = ‒‒‒,
L
here, L is the solvent motion front (cm), and li is the
distance from the starting line to the spot center of ith
component of the mixture being analyzed (cm) in the
chromatogram.
The presence of succinic acid in the products of EDSA,
IDSA and DCHDSA destruction was determined by the
standard method via 1D ascending paper chromatography
with a mixed solvent (18 : 2 : 9 mixture of butanol-1, formic
acid, and water), with succinic acid as a “witness.” On be-
ing dried, the chromatograms were developed by spraying
with 0.05% solution of Bromophenol Blue in ethanol.
Samples of complexons and photodestruction products
dried at a temperature of 40°C and prepared as pellets
with potassium bromide were examined by IR Fourier
spectroscopy on a Bruker Equinox 55 spectrometer in
the range 400–4000 cm–1 with resolution of 4 cm–1 at 32
scans. The absorption bands were identified on the basis
of published data [7].
RESULTS AND DISCUSSION
On being exposed to UV radiation, samples of solu-
tions of all the five complexons gave a positive reaction
with the Nessler reagent for the presence of ammonium
ions. This result indicates that the ligands are deaminated.
1D ascending paper chromatography with a 4 : 1 : 1
mixture of butanol-1, acetic acid, and water was used
in the presence of “witnesses” to determine the amino
acid composition of products formed in destruction of
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DEGRADATION OF COMPLEXONS DERIVED FROM SUCCINIC ACID
509
Table 2. Destruction of complexons upon 60-min exposure to UV radiation (T = 22 ± 1°C, pH 5.6)
Content of chelating substances
in solution upon UV
Δw of chelating substances
Initial concentration of a
complexon in solution, c1, M
Complexon
upon UV irradiation, % relative
irradiationa, w = c2/c1 100%
to the initial amount
EDTA
IDAA
1.00 × 10–2
1. 02 × 10–2
1.04 × 10–2
9.99 × 10–3
1.00 × 10–2
99.56 ± 0.03
84.38 ± 0.05
90.01 ± 0.21
82.60 ± 0.20
84.24 ± 0.26
0.44
15.62
9.99
EDSA
IDSA
17.40
15.76
DCHDSA
a w is the residual content of chelating substances relative to the initial content of a complexons in solution, taken to be 100%, Δw = 100% – w;
c2 is the concentration of chelating substances in solution upon exposure to UV radiation, M.
Table 2 lists the residual concentrations of the ligands in
percent relative to the initial value.
stances upon a partial destruction of the starting ligands.
The partial destruction of CDSAs is confirmed by IR
spectroscopic data (Figs. 1–3, Table 3).
It can be seen in Table 2 that complexons of the mono-
amine type are destructed to the greatest extent: IDSA,
IDAA, and a derivative of trans-1,2-diaminocyclohexane,
DCHDSA, which can be attributed to the structural fea-
An analysis of IR spectra of EDSA and products of
its destruction (Fig. 1) demonstrated that the absorption
band at 1724 cm–1, associated with protonated carboxy
tures of these ligands. The slight change in the EDTA groups, disappears from the spectrum of the destruction
concentration as a result of the UV irradiation indicates
that the primary products formed when this substance
is decomposed (ethylenediaminetriacetic and ethylene-
diamineacetic acids, EDTA [6]) also have a significant
chelating capacity. It can be assumed that this also refers
to a certain extent to products formed in the destruction
of CDSAs.
products (spectrum 2), and the intensity of the absorption
bands at 1633 and 1608 cm–1 decreases. This indicates
that the decarboxylation and deamination processes
occur under the action of UV radiation. The number
of absorption bands at wave numbers in the ranges
1180–1440 cm–1 and 2500–3400 cm–1, associated with,
respectively, bending and stretching vibrations of C–H
and N–H groups, substantially decreases in the spectrum
of products formed in destruction of EDSA, which is a
The method of complexometric titration was used to
determine the residual concentration of chelating sub-
T, %
T, %
ν, cm–1
ν, cm–1
Fig. 2. IR transmission T spectra of (1) IDSA and (2) products
of its destruction.
Fig. 1. IR transmission T spectra of (1) EDSA and (2) products
of its destruction. (ν) Wave number; the same for Figs. 2 and 3.
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SMIRNOVA et al.
Table 3. Characteristic absorption bands (cm–1) in IR spectra of EDSA, IDSA, DCHDSA, and their destruction products
υ
υas
(С–О)
υs
(С–О)
δ
υ
δ
υ
Product being analyzed
EDSA
(С=О)
(N–H)
(C–N)
(C–H)
(C–H)
1724
1633
1410
1397
1385
1608
1076
1038
1230
1244
1202
1185
2970
2933
2857
Products of EDSA destruction
IDSA
–
1628
1637
1398
1591
–
1064
1208
2927
2856
1714
1412
1088\
1220
1312
1126
3419
3079
Products of IDSA destruction
–
1623
1393
1086
1258
1393
1196
3401
2927
DCHDSA
1724
1724
1659
1647
1392
1391
1078
1250
1322
1219
2931
2866
Products of DCHDSA destruction
1562
1072
1252
1217
1138
2941
2867
consequence of the structural simplifications in molecules
of the substances being formed.
absorption at 2500–3400 cm–1 decreases, which indicates
that the content of carboxy and amino groups in the prod-
ucts formed in the photodestruction of the complexons
becomes lower.
Comparison of the IR spectra of IDSAand its decom-
position products (Fig. 2) points to a certain similarity
of the decomposition processes occurring in EDSA and
IDSA. For example, the absorption band (1714 cm–1)
associated with protonated carboxy groups is also absent
in the spectrum of the IDSAdestruction products and the
According to IR spectroscopic data (Fig. 3),
DCHDSA is also partly destructed. The spectra exhibit
changes associated with the decrease in the content of
N–H groups in the destruction products (stretching and
bending vibrations of N–H groups at, respectively, 3109
and 1562 cm–1) and in that of C=O groups (1724 and
1656 cm–1). Substantial changes in the spectra being
analyzed are also observed in the range 1033–400 cm–1,
which evidences that DCHDSA decomposes under the
action of UV radiation. It can be assumed that DCHDSA
decomposes via deamination and decarboxylation.
T, %
Some main destruction products were identified by
1D paper chromatography. The results of a qualitative
chromatographic determination of the amino acid com-
position of the products formed in the destruction of the
CDSAs under study are listed in Table 4.
Succinic acid was found by paper chromatography in
the products of IDSA, EDSA, and DCHDSAdestruction.
After the chromatograms were developed with 0.05%
solution of Bromophenol Blue in ethanol together with
a “witness,” there appeared characteristic yellow spots.
ν, cm–1
Fig. 3. IR transmission T spectra of (1) DCHDSAand (2) prod-
ucts of its destruction.
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DEGRADATION OF COMPLEXONS DERIVED FROM SUCCINIC ACID
511
Table 4. Results of a chromatographic analysis of the amino acid composition of products formed in EDSA, IDSA, and DCHDSA
destruction in the system constituted by butanol-1, acetic acid, and water (4 : 1 : 1) at T = 22 ± 1°C.
“Witness”
Product of destruction
IDSA
EDSA
spot color
DCHDSA
spot color
Rf
amino acid
spot color
Rf
Rf
Rf
spot color
–
Asparagine
Aspartic acid
Glycine
0.42
0.48
0.51
0.59
0.73
0.82
Dark violet
Violet
–
0.46
–
–
–
0.48
–
0.40 Dark violet
0.45 Violet
Violet
Violet
Lilaceous
Yellow
–
–
–
–
–
–
Serine
0.59
0.73
0.82
Brownish yellow 0.60
Pinkish lilaceous 0.73
Pinkish lilaceous 0.82
Yellow
α-Alanine
β-Alanine
Lilaceous
Lilaceous
Pinkish lilaceous 0.73 Lilaceous
Pinkish lilaceous 0.82 Lilaceous
The observed decomposition products of IDSA, EDSA
and, partly, DCHDSA(amino acids, carboxylic acid, am-
monium ions) are not only nontoxic for microorganisms,
plants, and animals, but also are their natural metabolites
and can be successfully absorbed by green plants and
microorganisms from soil and aqueous media. It remains
unclear whether products formed in partial decomposition
of DCHDSA, which contain a cyclohexane moiety, can
undergo natural degradation in the environment, which
invites a separate additional study.
ACKNOWLEDGMENTS
The study was financially supported by the Ministry
of Education and Science of the Russian Federation un-
der a State assignment in scientific activities (project no.
4.5508.2017/BCh) on the equipment of the Collective
Use center at Tver State University.
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