126
3 Traceability: Reference Materials
2. QUANTITATIVE ANALYSIS
Calibration
Methods
Equipment
Method
Absolute
<=Gravimetry, (Oulometry, isotope
.§
dilution mm spectrometry
Q:
Stoichiometric
(TiUlmetry)
rn
Relative
Most mstrumentaltechniQues
As shown in Fig. 3.11, method calibration applies to methods and differs
among CMPs, whereas equipment calibration pertains to instruments (or apparatuses) and can be shared by many CMPs. In practice, the word "calibration"
is used indifferently to refer to both chemical metrological goals. This improper
usage has been promoted by assimilation from physical metrological processes,
where no such distinction exists. Note the equivalence in this respect between
PMPs and absolute methods (e.g. gravimetry).
One special metrological operation in this context is so-called "internal
standardization", intended to avoid fluctuations in instrument readings. Box
3.13 summarizes its features and provides a representative example corresponding to the notation MC-3 in Fig. 3.9.
Correct
+
Incorrect
but widely
+
used
Fig. 3.11. Usage of the word "calibration" in chemical metrology