Seminar
139
I Seminar 3.1
Traceability in Calculable Analytical Methods
• Learning objective
To find ways to realize traceability in CMPs based on calculable methods, with
and without the use of analytical chemical standards.
• Specific examples
• Gravimetric determination of the iron content in a mineral by precipitation as a basic salt and weighing as ferric oxide.
• Determination of an oxidant in a food sample by addition of iodide ion and
titration of the iodine formed with a thiosulphate solution (a secondary
standard) previously standardized with KI03 (a primary standard).
• Literature
Examples in suggested reading no. 1.
• Traceability to what?
Based on the metrological features of the methods, the last links in the chains
of comparisons should be SI units (the kilogram or mole).
• Traceability paths
Explain the different available alternatives: equipment calibration, use of
CRMs and comparison with other primary methods.
• Equipment calibration
Check that the equipment used to make the measurements (mass, volume,
etc.) operates as expected. Note that no method calibration is necessary.
• Standards involved
What types of standards are required in each case? How are they linked to SI
units?
• Traceability chart
Draw a scheme showing the chains of comparisons as far as the SI units in
both cases.
• State traceability
Write a report describing how traceability to each CMP was realized.
Seminar 3.2
Traceability in Relative Analytical Methods
• Learning objective
To find ways to realize traceability in a CMP by establishing the signal-concentration relation (calibration curve).
• Specific example
Determination of cadmium traces (ng/g) in sea water. The CMP of choice
preconcentrates the metal traces on a chelating resin, elutes the metal
with HN03 and quantifies Cd2+ by atomic absorption spectroscopy. Find an
139
I Seminar 3.1
Traceability in Calculable Analytical Methods
• Learning objective
To find ways to realize traceability in CMPs based on calculable methods, with
and without the use of analytical chemical standards.
• Specific examples
• Gravimetric determination of the iron content in a mineral by precipitation as a basic salt and weighing as ferric oxide.
• Determination of an oxidant in a food sample by addition of iodide ion and
titration of the iodine formed with a thiosulphate solution (a secondary
standard) previously standardized with KI03 (a primary standard).
• Literature
Examples in suggested reading no. 1.
• Traceability to what?
Based on the metrological features of the methods, the last links in the chains
of comparisons should be SI units (the kilogram or mole).
• Traceability paths
Explain the different available alternatives: equipment calibration, use of
CRMs and comparison with other primary methods.
• Equipment calibration
Check that the equipment used to make the measurements (mass, volume,
etc.) operates as expected. Note that no method calibration is necessary.
• Standards involved
What types of standards are required in each case? How are they linked to SI
units?
• Traceability chart
Draw a scheme showing the chains of comparisons as far as the SI units in
both cases.
• State traceability
Write a report describing how traceability to each CMP was realized.
Seminar 3.2
Traceability in Relative Analytical Methods
• Learning objective
To find ways to realize traceability in a CMP by establishing the signal-concentration relation (calibration curve).
• Specific example
Determination of cadmium traces (ng/g) in sea water. The CMP of choice
preconcentrates the metal traces on a chelating resin, elutes the metal
with HN03 and quantifies Cd2+ by atomic absorption spectroscopy. Find an