Bismuth(V) oxide and silver bismuthate as oxidizing agents for gas-chromatographic elemental microanalysis

Article abstract of DOI:10.1023/B:RJAC.0000044176.90962.12

Bismuth(V) oxide, silver bismuthate, and a mixture of bismuth(V) oxide with fine silver powder were studied as oxidizing additives in gas-chromatographic elemental microanalysis of readily combustible organic substances and coal.

Full text of DOI:10.1023/B:RJAC.0000044176.90962.12

Russian Journal of Applied Chemistry, Vol. 77, No. 7, 2004, pp. 1200 1202. Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 7,
2004, pp. 1215 1217.
Original Russian Text Copyright
2004 by Shvykin, Platonov, Proskuryakov, Chilachava, Khmarin, Kovtun.
BRIEF
COMMUNICATIONS
Bismuth(V) Oxide and Silver Bismuthate as Oxidizing Agents
for Gas-Chromatographic Elemental Microanalysis
A. Yu. Shvykin, V. V. Platonov, V. P. Proskuryakov, K. B. Chilachava,
E. M. Khmarin, and I. V. Kovtun
Tolstoy State Pedagogical University, Tula, Russia
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received June 24, 2003; in final form, April 2004
Abstract Bismuth(V) oxide, silver bismuthate, and a mixture of bismuth(V) oxide with fine silver powder
were studied as oxidizing additives in gas-chromatographic elemental microanalysis of readily combustible
organic substances and coal.
Gas-chromatographic elemental analysis (GCEA) is
one of fast and automated methods for analyzing
organic compounds. The accuracy and reproducibility
of this method are comparable with, and sometimes,
exceed those of conventional elemental analysis.
Ag O, AgMnO , AgVO , Ag Cr O , and Ag O ) are
2 4 3 2 2 7 2 2
both oxygen donors and oxidation catalysts. Among
compounds of the third group, silver-containing sub-
stances AgMnO and Ag O are the most effective.
4
2 2
Metallic silver formed in their thermolysis is a very
active catalyst for surface oxidation of the organic
component of organoelemental compounds as well as
high-ash and high-carbon caustobioliths. These oxi-
dizing agents are suitable for highly effective and
complete combustion of difficultly combustible sam-
ples in GCEA. The procedure of GCEA of solid caus-
tobioliths, with coals as example, using a Carlo Erba-
1100 elemental analyzer was developed and optimized
in [4]. AgMnO , PbO , Ar Cr O , and Ag O were
One of serious problems of GCEA is efficient and
almost instantaneous oxidative thermolysis of an
organic sample to form products suitable for chroma-
tographic analysis. To provide compete oxidation of
a sample, appropriate oxidizing agents or their mix-
tures with combustion catalysts are added to the
sample, and oxidation is performed in a carrier gas
(usually helium) containing oxygen. A wide range of
oxidizing agents and combustion catalysts providing
reliable and complete oxidation of a sample are used
in modern GCEA. However, frequently samples of
organoboron, organosilicon, and organogermanium
compounds, salts of polybasic carboxylic acids, salts
of sulfonic acids, various solid caustobioliths, and
their derivatives (lignite, coal, peat, sapropels, humic
acids, and their extracts) are incompletely burnt
in the presence of these oxidizing agents. This is due
to high content of mineral fraction (up to 95%) in
these materials. Therefore, a search for new effective
oxidizing agents and combustion catalysts for dif-
ficultly oxidizable organoelemental compounds and
solid caustobioliths is an urgent problem.
4
2
2
2
7
2 2
studied as oxidizing catalysts for sample combustion.
The most effective were AgMnO , PbO , and Ag O .
4
2
2 2
In addition, the procedures for weighing and pretreat-
ment of the samples were substantially modified, and
mathematical treatment of the chromatrograpms was
improved. As a result, the accuracy and reproducibil-
ity of the analysis sharply increased.
Bismuth(V) compounds, Bi O , and AgBiO , have
2
5
3
not been used as oxidizing agents for GCEA. We
suggest that bismuth(V) oxide should be an active
oxygen donor; AgBiO should be both an oxygen
3
donor and a catalyst of surface oxidation owing to
the presence of silver in its composition. The influ-
ence of catalytic additives of fine metallic silver
powder on the oxidizing power of inorganic com-
pounds that are used in modern GCEA as oxygen
donors but are not oxidation catalysts was not fully
understood. In this work we studied synthesis of
bismuth(V) oxide and silver bismuthate and tested
these compounds as oxidizing agents for GCEA. We
Diverse inorganic compounds and their mixtures
were studied as oxidizing additives to samples to be
burnt up [1 4]. Some of them such as PbO and
2
MnO are oxygen donors. Other compounds, e.g.,
2
NiO, Cr O , WO , and CeO are surface combustion
2
3
3
2
catalysts. Compounds of the third groups (V O ,
2
5
1070-4272/04/7707-1200 2004 MAIK Nauka/Interperiodica

BISMUTH(V) OXIDE AND SILVER BISMUTHATE AS OXIDIZING AGENTS
1201
Average results of elemental analysis of p-nitrophenol and coal of Yakutiya basin in the presence of the oxidizing agents
p-Nitrophenol, %
Coal, %
H
Oxidizing agent
C
H
N
C
N
AgMnO4
Bi2O5
Bi2O5 + Ag
AgBiO3
Calculated data
51.83
51.79
51.81
51.82
51.80
3.58
3.55
3.57
3.63
3.60
10.05
10.05
10.06
10.08
10.07
68.37
54.01
68.24
57.08
68.38*
5.18
5.06
5.21
5.17
5.19
0.20
0.23
0.21
0.21
0.20
* Determineded by conventional elemental analysis
also studied the influence of catalytic additives of fine
metallic silver powder on the oxidizing properties of
these compounds in combustion of microamounts of
difficultly combustible samples.
NH OH. The resulting mixture was thoroughly ground
4
in an agate mortar and stored without air access.
The weight fraction of Ag(0) in the mixture was
22.56 wt %.
Bi O , AgBiO , and Bi O + Ag(0) were studied
as oxidizing additives to samples for GCEA. We also
2
5
3
2 5
EXPERIMENTAL
studied AgMnO as reference effective oxidizing
4
-Bi O was prepared by treatment of NaBiO
3
agent. The organic compound to be analyzed was
p-nitrophenol. Coal of Yakutiya basin was used as
the sample of difficultly combustible high-carbon
caustobiolith. The average rounded weight (mg) of
Bi O , AgBiO , Bi O + Ag(0), and AgMnO added
2
5
2H O with a large excess of 68% HNO at 15 C for
2
3
1 h [5 7]:
2NaBiO3 2H2O + 2HNO3 + (n 5)H2O
Bi2O5 nH2O
2
5
3
2
5
4
to the sample was 9.6, 11.4, 28.5, and 43.7, respec-
tively, with their volume being approximately the
same. The chromatographic analysis and mathematical
treatment of the results were performed by the proce-
dure in [4]. The results of the elemental analysis are
summarized in the table.
+ 2NaNO3.
After reaction completion, excess HNO was
neutralized to pH 7 with an NaHCO solution cooled
3
3
to 0 C. The Bi O nH O precipitate was filtered off,
2
5
2
washed many times with water, and predried at 20 C
Since Bi O and AgBiO are loose powders, their
for 48 h over freshly calcined CaCl . Anhydrous
bismuth(V) oxide was prepared by drying Bi O
nH O at 105 C for 10 h in a drying oven:
2
5
3
2
bulk density is minimal among the examined oxidiz-
2
5
ing agents. AgMnO has the highest bulk density.
4
2
The bulk density of Bi O increases by a factor of
2
5
approximately 3 after addition of Ag(0), i.e., addition
of Ag(0) increases the Bi O amount in the sample,
Bi2O5 nH2O
Bi2O5 + nH2O.
2
5
on the average, by a factor of 2.3. Hence, the amount
of active oxygen liberated in thermolysis of Bi O
AgBiO was prepared by reaction of 28-fold excess
3
3
of AgNO with NaBiO 2H O in an aqueous solution
2
5
3
2
increases by the same factor, which should make oxi-
dation of the sample more complete. Thus, the in-
crease in the bulk density of Bi O after grinding with
at 20 C for 1 h [5]:
NaBiO3 2H2O + AgNO3
AgBiO3 + NaNO3 + 2H2O.
2
5
fine Ag(0) powder should increase the completeness
of sample combustion owing to an increase in the
amount of the oxidizing agent added to the sample,
even if there were no catalytic effect of Ag(0).
The AgBiO precipitate was filtered off, washed
many times with distilled water, and predried at 20 C
3
for 48 h over freshly calcined CaCl . Anhydrous
2
AgBiO was obtained by heating at 60 C for 24 h
3
As seen from the table, the results of elemental
analysis of p-nitrophenol, performed with all the
tested oxidizing agents, agree with each other and
with the calculated values. Hence, all these oxidizing
agents can be used in GCEA of readily combustible
organic compounds like p-nitrophenol (or their mix-
in a drying oven.
To study the influence of catalytic amounts of
silver on the oxidation power of Bi O , bismuth oxide
2
5
was mixed with fine silver powder prepared by reduc-
tion of [Ag(NH ) ]Cl with N H HCl in excess
3 2
2 4
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 77 No. 7 2004

1202
SHVYKIN et al.
tures). On the contrary, the carbon contents in coal de-
termined in the presence of these compounds strong-
ly differ. Only nitrogen and hydrogen contents are
consistent. The carbon content determined with Bi O
The carbon content in coal, determined with bis-
muth(V) oxide and silver bismuthate, is lower than
that determined in the presence of AgMnO . The car-
4
bon content determined with Bi O + Ag(0) mixture
2
5
2
5
is close to that determined with AgMnO . This mix-
(54.01% C) is lower by 14.36% than that determined
4
ture can be used as oxidizing additive in gas-chroma-
tographic analysis of solid caustobioliths.
with AgMnO (68.37% C). The carbon content deter-
4
mined in the presence of AgBiO (57.08% C) is
3
underestimated by 11.29%. The results obtained with
a Bi O + Ag (68.24% C) mixture are close to those
REFERENCES
2
5
obtained with AgMnO . Hence, addition of fine Ag(0)
4
1. Metody kolichestvennogo organicheskogo elementnogo
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Khimiya, 1987.
2. Berezkin, V.G., Khimicheskie metody v gazovoi khro-
matografii (Chemical Methods in Gas Chromatog-
raphy), Moscow: Khimiya, 1980.
powder sharply increases the oxidizing power of
Bi O under GCEA conditions. This mixture can be
used to analyze difficultly combustible materials like
caustobioliths. Probably, Ag(0) can also enhance the
2
5
oxidizing power of AgBiO and other compounds.
3
CONCLUSIONS
3. Childs, C.E. and Henner, E.B., Microchem. J., 1966,
vol. 10, no. 3, pp. 402.
(1) Bismuth(V) oxide, its mixture with fine silver
powder, and sliver bismuthate can be used as effective
oxidizing agents for combustion of readily com-
bustible organic compounds in chromatographic ele-
mental microanalysis.
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mined in coal samples by gas-chromatographic ele-
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Bi(V) compounds and their mixtures are consistent.
6. Martin-Frere, H., Chem. Rev., 1941, vol. 213, no. 4,
pp. 436 437.
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