2007 Inter Laboratory Comparisons
As part of our quality system we participate in inter laboratory comparisons. One such scheme is the ‘Food analysis using Isotopic Techniques – Proficiency Testing Scheme’. The first sample we analysed in 2007 was a wheat flour which required measurement of both carbon-13 and nitrogen-15. The charts below show the ‘Z scores’ of each laboratory. Essentially the Z score indicates how close a laboratory came to achieving the ‘robust mean value’ (excludes outliers) during the test. The closer your value is to zero, the closer you were to the robust mean. Laboratories with a Z score near to zero are near the middle of the chart.
Our Z score was close to zero for both the carbon-13 and nitrogen-15 measurements. Our position in the chart is highlighted by the red block (we are identified as lab1 for this study)
Later in 2007 we were involved in an inter laboratory comparison for the measurement of carbon-13 in honey. The requirement here was to measure the carbon-13 signature of the honey as a whole and to measure the carbon-13 of protein that we were required to extract from it. This is exactly the same as the ‘carbon-13 honey test’ that we provide clients with on a regular basis.
Again Iso-Analytical achieved close to zero Z scores which are identified by the red blocks in the charts below but this time we were allocated the code of lab2.
The excellent Z scores we achieved in these tests are testament to both the accuracy of our analytical methods and the laboratory standards we use during the analyses.