Analysis of the iron state in iron containing
medicines by Mössbauer spectroscopy
P.Szalanski1, R.Brzozowski1, M.Pruba1, P.Wierzbianski1,
Yu.M.Gledenov2, P.V.Sedyshev2, A.Oprea2
1
2
University of Lodz, Poland
Joint Institute for Nuclear Research, Dubna, Russia
Introduction
Iron is an essential metal and is an active site in
hemoglobin, myoglobin, cytochromes, catalase, and other
iron containing proteins that realize oxygen and electron
transport and enzyme functions. Iron deficiency causes
anemia and other pathological effects in the body and iron
containing medicines, including oral iron containing vitamins
and dietary supplements or injectable pharmaceuticals, are
used in order to prevent and treat iron deficiency. A
knowledge of the chemical states of iron in these products is
very important because this may determine its effect and
toxicity. For instance, ferrous compounds are more
bioavailable than ferric ones for oral iron containing
supplements [1,2,3].
Mössbauer spectroscopy
Mössbauer spectroscopy is a sensitive technique for
determining the iron oxidation state. Numerous studies of
the iron containing species demonstrated possibilities of
Mössbauer spectroscopy in various fields of chemistry,
biology and medicine. Mössbauer spectroscopy allows to
observe the hyperfine splitting of the nuclear energy levels
as well as changes of energies of the ground and excited
states of Mössbauer nuclei (57Fe in our case) in the
absorption or emission spectrum of γ-rays. The typical
Mössbauer parameters which can be obtained from
Mössbauer spectra are isomer shift, IS, quadrupole splitting,
QS, magnetic hyperfine field, Heff, line width, Γ, intensity and
area of the spectral lines [1,4].
The IS value is related to the electron density at the
57Fe nucleus. The QS value is related to the electric field
gradient tensor at the 57Fe nucleus. The Heff value is the
effective magnetic field at the 57Fe nucleus. The Γ value
reflects information related to homogeneity of sample and
dynamic processes. Intensity and absorption area are related
to the mean square displacement of the 57Fe nucleus and
quantity of the 57Fe nuclei. In general, isomer shift and
quadrupole splitting give information about the iron electronic
structure, valence and spin state while absorption area gives
information about relative content of various iron compounds
in the sample. Therefore, Mössbauer spectroscopy was
applied in biomedical research, in particular for analysis of the
iron containing pharmaceutical compounds [1].
A Mössbauer spectrometer has rather simple setup, and
typically consists of a γ-ray source, the absorber (sample) and
a detector. The source is moved relative to the absorber,
shifting the energy spectrum due to the Doppler effect. For our
study 57Fe (14.41 keV transition, ~ 25 mCi of activity) was
used. The radioactive isotope is usually incorporated in a host
material such that its levels remain unsplit. The sources used
for this work were 57Co:Rh. All presented measurements were
performed at the room temperature in transmission geometry.
Experimental results and discussion
Two different commercially available ferrous ironcontaining samples were studied. The ferrous gluconate
(ASCOFER®, ESPEFA) and ferrous sulfate (HEMOFER®,
GLAXOSMITHKLINE) samples were used, first had the outer
coating removed. Figs. 1-2 and Tab. 1 present our results.
Tab. 2 presents comparison of our date and earlier
measurements.
Fig. 1. Mössbauer spectrum of ferrous gluconate (ASCOFER®, ESPEFA). Components (1) and
(2) are ferrous gluconate compounds, component (3) is ferric compound (T=295 K).
Fig. 2. Mössbauer spectrum of ferrous sulfate (HEMOFER®, GLAXOSMITHKLINE).
Component (1) is ferrous sulfate compound (T=295 K).
Samples
IS [mm/s]
QS [mm/s]
Area (%)
Compound
ASCOFER®
1.23345(87)
3.1271(30)
64.39(18)
Ferrous gluconate
(1)
1.1921(44)
2.698(17)
25.48(21)
Ferrous gluconate
(2)
0.397(17)
0.803(30)
9.13(46)
Ferric high spin
(3)
1.29307(56)
2.8214(11)
100
Ferrous sulfate (4)
ASCOFER®
ASCOFER®
HEMOFER®
Table 1. Mössbauer parameters of ferrous gluconate (ASCOFER®, ESPEFA) and
ferrous sulfate (HEMOFER®, GLAXOSMITHKLINE) samples measured at 295 K.
Samples
IS [mm/s]
QS [mm/s]
Reference
Ferrous gluconate
70/20% Fe2+
10% Fe3+
1.22/1.18
0.45
3.1/2.7
0.7
[5]
[5]
Ferrous gluconate
~ 65/25% Fe2+
~ 10% Fe3+
1.23/1.19
0.40
3.1/2.7
0.8
This work
This work
Ferrous sulfate
1.26
2.69
[5]
Ferrous sulfate
1.29
2.82
This work
Table 2. A comparison of the room temperature Mössbauer data
Authors observed about 9% of ferric compounds in the
sample containing ferrous gluconate that they attributed to
ferric gluconate. Up to now we didn’t received technical
specification from manufacturer, but on the other hand the
presence of ferric iron was not be higher than 2% according
to international requirements. Thus, Mossbauer spectroscopy
may be useful for the control of the iron compounds and their
content in iron containing medicines.
Our date are in good agreement with the earlier
measurements.
Conclusions
Mössbauer spectroscopy demonstrates wide possibilities for analysis of the iron containing compounds, the iron
electronic structure, valence and spin states and relative
content of these compounds in the sample. This technique
can be useful for studying various species including
pharmaceutical and biological subjects and in biomedical
research [6].
Measuements of the iron state in iron containing
vitamins (ferrous sulfate, FALVIT®, JELFA and ferrous
fumarate, MATERNA®, WYETH) are in progress.
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