Estimating measurement uncertainty using a cause and effect and reconciliation approach Part 2. Measurement uncertainty estimates compared with collaborative trial expectation

Measurement uncertainty estimates are presented for ten analytical methods, covering over 45 combinations of analyte, matrix and concentration. The uncertainty estimates were produced using a cause and effect approach published previously. Techniques include gas and liquid chromatography, elemental analysis by graphite furnace atomic absorption spectrometry, inductively coupled plasma-mass spectrometry, inductively coupled plasma-optical emission spectrometry, and titrimetry. A range of different types of data is used, including quality control data and method validation studies. The major contributions to the uncertainty for each method and a brief description of their evaluation are given. In most cases, a combination of an experimental estimate of overall precision and the uncertainty associated with overall bias, measured as recovery, across representative sample types and analyte concentrations contributes the majority of the uncertainty, although in several cases it was essential to consider additional factors. The uncertainty estimates are also compared with collaborative trial results where available, and with reproducibility estimates obtained from the Horwitz function.