What is calibration?

1) What is traceability? 2) How is this traceability achieved with Starna®range of Certified Reference Materials? Before answering these questions, we must establish what is meant by "Calibration", and why is it important?

What is calibration?

Calibration is the process of establishing how the response of a measuring device varies with respect to the instrument parameter being measured. The usual way to perform calibration is to measure the parameter (e.g. using a reference material) and monitor the instrument response.

Why is it important?

Place any equipment in the environment of choice, and immedi­ately the chosen environment will begin to act on that equipment causing change; and ultimately degradation in performance. This so called drift, causes your results to become unreliable and no longer "fit for their intended purpose". Whilst drift cannot be eliminated it can be detected and contained through the process of calibration. In the pharma­ceutical industry, a system where drift has occurred to an unacceptable level is deemed to be "out of control".

By inference, this same environment will also act on your Certified Reference Materials to a greater or lesser degree, depending on how they are stored, etc. and these materials must be checked/re-certified to ensure that the values on which you are depending have not also significantly changed.

What is traceability?

National Standards Laboratories (NIST, NPL, etc.) work together to agree a common definition for measurement units. These then make up the International System of units, SI. e.g. kilogram, second, metre, ampere, candela, and the Standards Laboratories will then "realise" units from internationally agreed SI definitions to establish primary national measurement scales. Traceability is defined in the "International Vocabulary of Basic and General Terms in Metrology (ISO, 1993)" as the."property of the result of a measurement of the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties."

How is this traceability achieved with Starna® materials?

Where appropriate, calibration certificates are issued where the certification process has established traceable links to a USA National Institute for Standards and Technology (NIST) Standard Reference Material (SRM) to determine the appropriate filter parameters. Using procedures consistent with the operation within an ISO 17025 environment, all certification measurements are bracketed by use of an appropriate NIST primary SRM. In addition the fundamental characteristic of the reference spectrophotometer are periodically established using physical references. For example, wavelength calibration is verified using line spectra from a mercury emission source.

What does traceability achieve?

Measurements are made against a consistent set of units and there is international equivalence of national measurement scales. It also means that compatible measurements are made across national borders, resulting in unambiguous and reliable communication of specifications.