Federal Institute for Materials Research and Testing,
Analytical Chemistry; Reference Materials,
Richard-Willstätter-Strasse 11, D-12489 Berlin/Germany
Tel. +49 30 8104 1100, Fax +49 30 8104 1117
Certificate no. U9-0416 for reference material
Supplier of the reference
material:
Sigma-Aldrich Production GmbH, Industriestrasse 25, CH-9471 Buchs, Switzerland
Object of certification:
Product no. 71804, Sodium oxalate: Na2C2O4 reductometric standard in 50 mL glass
bottles, screw caps; batch no. BCBR5525V
Certification report no. 1170/XII1, BAM Berlin
Intended use:
This reference material is intended for use as reductometric standard and cannot be
employed as purity standard.
Storing and handling:
Ensure that the reference material is stored in the dark (i.e. within the packaging of
the bottle) at temperatures in the range of 5°C to 30°C. Before any use as a
reference material, it has to be dried for 3 hours at 105°C. It should be used after the
bottle is opened according to established rules in analytical chemistry (i.e. to
guarantee that no contamination can occur). The use of samples less than 120 mg is
prohibited in order to avoid possible inhomogeneities with smaller sample sizes (see
part. 2 of certification report).
Number of pages of this
certificate:
1
Annex:
Certification report no. 1170/XII1 (2 pages), BAM Berlin, as part of this certificate
Expiry date:
26. April 2021
5
Certified value and its measurement uncertainty according to ISO Guide 35:
1
Constituent (formula) and relative
Expanded uncertainty
Certified value
molar mass for reporting
Coverage factor = 2
Sodium oxalate
Na2C2O4
4
Mr = 133.9985
2, 6
w = 99.86%
3
0.9986 mol/mol
Methods of analysis
2, 6
± 0.09 %
3
± 0.0009 mol/mol
redox titration
1 See Eurachem / CITAC Guide „Quantifying Uncertainty in Analytical Measurement“, Second Edition, 2000
ISBN 0948926155. Internet: http://www.measurementuncertainty.org
2 Mass content of reductometric standard, calculated as sodium oxalate
3 Fraction of measured molar amount in relation to the theoretical value referring to 100% sodium oxalate
4 Relative molecular mass: Pure Appl. Chem., Vol. 78, No. 11, pp. 2051–2066, 2006
5 Expiry date is based on stability tests carried out at Empa, Swiss Federal Laboratories for Materials Testing and Research, St. Gallen/Switzerland
6 The certified value and the corresponding uncertainty are rounded according to DIN 1333, 1992
The responsibility for this certificate in case of any inquiry lies only with BAM Berlin.
Berlin, 26. April 2016
BAM Berlin/Germany
Head of Department Analytical Chemistry; Reference Materials
Prof. Dr. U. Panne
This certificate is valid for the mentioned batch of the originally sealed containers only, under the condition that the storing and handling
instructions are adhered to. The use of certificates for purposes of advertising, including a mere reference as well as a partial publication, require
the approval of BAM. Certificates together with the respective documents will be kept in the archive for ten years. For sale or other distribution of
the certified product the relevant laws and regulations apply.
Federal Institute for Materials Research and Testing,
Analytical Chemistry; Reference Materials,
Richard-Willstätter-Strasse 11, D-12489 Berlin/Germany
Tel. +49 30 8104 1100, Fax +49 30 8104 1117
Certification report no. 1170/XII1
Combined standard uncertainty:
u
c
=
u
2
BAM
2
+ u Inhom = 0.041 2 + 0.015 2 = 0.044 %
This report comprises two pages.
Sigma-Aldrich Production GmbH produced Product no. 71804, Sodium oxalate (Na2C2O4), batch no. BCBR5525V
as reductometric standard. Sigma-Aldrich Production GmbH filled a total number of 550 glass bottles each with 25 g
of batch material. The sampling of the randomly chosen flasks for certification analyses was done by Sigma-Aldrich
Production GmbH.
The determination of the content of the reductometric standard and the assessment of the homogeneity of the whole
production of 550 glass bottles was performed on twenty randomly chosen flasks applying the volumetric redox
titration as primary analysis method. All measurements were carried out between March 16, 2016 and April 22, 2016
in a temperature range of 22°C ± 2°C.
Content of the reductometric standard
value:
99.857 %
1
0.99857 mol/mol
2
Expanded uncertainty 2 uc
value:
0.088 %
1
0.00088 mol/mol
2
Berlin, 26. April 2016
BAM Berlin/Germany
Head of Division Inorganic Reference Materials
1. Content of the reductometric standard by volumetric redox titration
Volumetric redox titrations with approx. 0.2 mol/l KMnO4-solution using a Pt-Titrode electrode were performed by
R. Meinhardt with a fully automatic sample preparation and data acquisition system. The work was carried out under
supervision of Dr. S. Recknagel. Samples of each of the twenty randomly chosen flasks, dried at 105°C for 3 hours,
and of eight separately prepared reference materials were dissolved and then titrated in one set. The results are
based on eight sets with titration of the weighed samples of sodium oxalate. All the measurements are traced
gravimetrically to National Institute of Standards and Technology (NIST) Standard Reference Material 8040 sodium
oxalate (99.951%, dried at 105°C for 3 hours).
Dr. S. Recknagel
1
Content of the reductometric standard
Standard uncertainty uBAM
value:
value:
1
99.857 %
1
0.041 %
2
0.99857 mol/mol
2
0.00041 mol/mol
2
3
Mass content of reductometric standard, calculated as sodium oxalate
Fraction of measured molar amount in relation to the theoretical value referring to 100% sodium oxalate
Accred. Qual. Assur., Vol. 6, pp. 274-277, 2001
2. Homogeneity of the reductometric standard
The homogeneity was investigated simultaneously with the content assessments using volumetric redox titration
during the eight experimental sets as described in part 1. For each of the twenty randomly chosen samples a
content of the reductometric standard was established. The inhomogeneity contribution to the uncertainty uInhom is
set to the experimentally determined between-bottle standard deviation as the best estimate of the uncertainty due
3
to between-bottle heterogeneity . The studies were performed by weight of contents using approximately 120 mg
samples of the reductometric standard. Therefore any use as a reference material below this limit is prohibited.
Standard uncertainty uInhom
value:
0.015 %
1
0.00015 mol/mol
2
The test results are valid solely for the batch of reference material tested. The use of the test reports for the purpose of publicity, the mere
reference to them or publication of excerpts require the approval of BAM. Test reports and supporting documents are retained for 10 years.