Vj. Barwick et Slr. Ellison, Measurement uncertainty: Approaches to the evaluation of uncertainties associated with recovery, ANALYST, 124(7), 1999, pp. 981-990
A number of approaches for evaluating recovery and its contribution to unce
rtainty budgets for analytical methods are considered in detail. The recove
ry, R, for a particular sample is considered as comprising three elements,
R,, R, and R,,. These relate to the recovery for the method; the effect of
sample matrix and/or analyte concentration on recovery; and how well the be
haviour of spiked samples represents that of test samples. The uncertainty
associated with R, u(R), will have contributions from u(R,), u(R-s) and u(R
,,). The evaluation of these components depends on the method scope and the
availability, or otherwise, of representative certified reference material
s. Procedures for evaluating these parameters are considered and illustrate
d with worked examples. Techniques discussed include the use of certified r
eference materials and spiking studies, and the use of extraction profiling
to predict recoveries. All the approaches discussed evaluate the recovery
and its uncertainty for the analytical method as a whole. It is concluded t
hat this is a useful approach as it reduces the amount of experimental work
required. In addition, most of the required data are frequently available
from method validation studies.