Simple visual examination of a reference material artifact used in spectrophotometer qualification does not allow the user to recognize or confirm its metrological quality for this intended purpose. The transparency of the scientific detail provided in the calibration certificate or report that accompanies the measurement standard is the only means in which the user can ensure that the “calibrated” reference material has the required metrological quality even when it is obtained from an accredited calibration laboratory. If the “calibrated” reference material is deemed to be lacking metrological quality, all UV/VIS spectrophotometer qualifications performed using this “calibrated” reference material can be readily challenged from a measurement quality assurance perspective and regulatory compliance may be jeopardized.
From a metrological perspective, it is imperative that the calibration certificate or report can provide evidence to substantiate the implied confidence in the assigned reference values and uncertainties even if the calibration certificate or report is issued by an accredited calibration laboratory. Transparency of the level of detail of the calibration process provided in the calibration certificate or report will determine whether or not the user of the measurement standard is indeed able to make this determination.
Several features of the calibration process need to be transparent and included in the calibration certification or report, some of which are described here: (i) measurement data to prove that the calibration spectrophotometer was in statistical quality control at the same time that the reference material artifact was actually calibrated, (ii) measurement data to prove that metrological traceability was established using appropriate science-based pathways at the same time that the reference material artifact was actually calibrated, (iii) development of a measurement uncertainty budget based on a rigorous procedural investigation and quantification of components of measurement bias and variation derived from instrument sources and filter material properties, and (iv) full disclosure of the calibration procedures and laboratory environmental conditions such that the actual calibration can be independently duplicated, if necessary. The development of uncertainty budgets based on an out-dated model that does not take into full account of the most important sources of measurement variability and bias can result in an unrealistically narrow uncertainty interval which subsequently leads to an over-estimation of the confidence in the interpretation of the measurement results.
In support of its measurement standards and services, Stranaska Scientific is pleased to provide independent assessments of calibration certificates or reports for customers that want to determine whether or not their reference material artifacts have the requisite metrological quality. By taking advantage of Stranaska’s unique experience and expertise in this area, customers can now have the peace of mind knowing that their spectrophotometer qualifications are not unwittingly challenged from a metrological perspective and that their laboratory program for regulatory compliance is not jeopardized.