What is calibration chain and traceability

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Traceability

definition
Traceability is the property of a measurement result, whereby a reference to a suitable standard (usually an international or national standard) can be established through an uninterrupted chain of comparisons.

A precondition for a traceability of measurement results is a previous calibration of the measurement process and a calibration of the measurement equipment.

For every analytical measurement, it should be possible to trace the measurement result back to a suitable national or international measurement standard through an uninterrupted chain of comparisons.

For weight measurements this would be the original kilogram in Paris, for the amount of a substance it should be the SI unit mole.

When a scale has been calibrated by a recognized person, it is an instrument for measuring weight based on national measurement standards.

Chemical analysis equipment must be calibrated using certified or other appropriate standard reference materials.

Further prerequisites for traceability of the measured values ​​are careful documentation and possibly specifications for the quality of the entire process.

example

Determination of lead in water by atomic absorption spectroscopy (AAS):

The AAS device must be calibrated using reference solutions that have been prepared by dissolving a known amount (initial weight) of a certified reference material (CRM) or a pure substance such as in a defined volume of pure water; in the second case, the pure substance must be compared with a CRM. A calibration curve covering the concentration range of the analyte should be generated.

For more complex analyzes, e.g. including extraction or other analytical procedures, the traceability of the measurement result can be achieved by subjecting a certified reference material - with a similar composition to the unknown sample - to the same analytical procedure.

If, for example, the measurement standard has not been compared with a CRM of the same type, the comparison chain is interrupted.