Pooled Calibrations with Its Limitations as an Alternative to Contemporary Methods of QA/QC

Only a few useful recommendations are available, as to the determination of the linear range of calibration. The unfeasible determination of the linear range is evaluated by the corresponding coefficient of regression that depends strongly on the number of data points to the calibration line. The limit of quantitation (LOQ) depends on the standard deviation of blanks that remains highly unreliable, owing to the only ten repetitions that are recommended for its determination. With the new system of QA/QC, that was developed and adopted by numerous national and international organizations, there is more focus on uncertainty of measurement, traceability and uncertainty budgets that allows for production of reliable predictions and delivery of consensus values. Despite good intentions and much effort, the new system of QA/QC is overly complicated and there are some serious shortcomings that need to be addressed. For a method validation with results of Flame-atomic absorption spectrometry equipped with a continuous source lamp, as an example, it is demonstrated that surprisingly large uncertainties were obtained, which contradicted the information that was provided by the manufacturer. By introducing the principle of pooled calibrations (PoPC) the elements Na(588 nm), K(766 nm), Mg(285 nm), Fe(248 nm), Ni(232 nm) and Cu(324 nm) were subjected to method validations. Generally, the lower limit of analysis (LLA) was found to be larger by more than an order of magnitude in comparison with the corresponding LOQ. The uncertainty of measurement as a function of concentration reached high levels thus effectively narrowing the analytical range of concentrations.