4.6 Validation of a Chemical Measurement Process
173
I 4.6 Validation of a Chemical Measurement Process
To validate is to demonstrate, in experimental and formal terms, that a general
(CMP) or particular system (e.g. the sampling or data acquisition and processing operations) has performed as expected and continues to do so. Also, to
validate is to experimentally and formally demonstrate that an object (an instrument, apparatus, device) possesses specific properties and retains them.
The validation of a CMP is of the exclusive concern of analytical quality
assessment systems (Chap. 8). A CMP can be validated for two essential
purposes, namely:
(a) To identify and assure quality (and constancy) in the analytical information
(results, reports) produced. This involves so-called internal validation, by
which a CMP is characterized via such properties as accuracy (traceability),
precision (uncertainty), selectivity, determination range, expeditiousness,
cost-effectiveness, robustness, etc.
(b) To ensure consistency between the analytical signal produced and the
information demanded by society, industry, trade, science or technology.
This external validation (Chap. 8) additionally allows one to categorize
(characterize) CMPs and analytical tools, facilitates quality audits, assures
transferability of CMPs and tools among laboratories, and encourages
harmonization and mutual acceptance of results among laboratories.
Figure 4.19 shows the different types of analytical systems and objects amenable
to validation, and ranks their obvious mutual relationships. At the first level of
the ranking is method validation; this rests on the second level, which comprises
validation of
(a) sampling processes;
(b) analytical tools (objects such as reagents, reference materials, instruments,
apparatus and devices); and
(c) data (hardware and software validation). Computer hardware, at the fourth
level of the ranking, can be an apparatus (e.g. a computer) or a device (e.g.
an interface).
A CMP can be internally validated in two different ways, namely:
(a) In a stepwise process involving validation of the analytical aspects at the
second, third and fourth level in Fig. 4.19; while this is labour-intensive and
time-consuming, it occasionally provides valuable specific information
about the particular instrument, sampling schedule, data, etc.
(b) By checking the CMP as a whole.
On the other hand, a CMP is externally validated by checking for consistency
between the results it produces and the information initially required.
A detailed description of validation procedures, of increasing use in the analytical chemical field, is beyond the scope of this introductory book on Analytical Chemistry. Note, however, that all validation processes share the need for
173
I 4.6 Validation of a Chemical Measurement Process
To validate is to demonstrate, in experimental and formal terms, that a general
(CMP) or particular system (e.g. the sampling or data acquisition and processing operations) has performed as expected and continues to do so. Also, to
validate is to experimentally and formally demonstrate that an object (an instrument, apparatus, device) possesses specific properties and retains them.
The validation of a CMP is of the exclusive concern of analytical quality
assessment systems (Chap. 8). A CMP can be validated for two essential
purposes, namely:
(a) To identify and assure quality (and constancy) in the analytical information
(results, reports) produced. This involves so-called internal validation, by
which a CMP is characterized via such properties as accuracy (traceability),
precision (uncertainty), selectivity, determination range, expeditiousness,
cost-effectiveness, robustness, etc.
(b) To ensure consistency between the analytical signal produced and the
information demanded by society, industry, trade, science or technology.
This external validation (Chap. 8) additionally allows one to categorize
(characterize) CMPs and analytical tools, facilitates quality audits, assures
transferability of CMPs and tools among laboratories, and encourages
harmonization and mutual acceptance of results among laboratories.
Figure 4.19 shows the different types of analytical systems and objects amenable
to validation, and ranks their obvious mutual relationships. At the first level of
the ranking is method validation; this rests on the second level, which comprises
validation of
(a) sampling processes;
(b) analytical tools (objects such as reagents, reference materials, instruments,
apparatus and devices); and
(c) data (hardware and software validation). Computer hardware, at the fourth
level of the ranking, can be an apparatus (e.g. a computer) or a device (e.g.
an interface).
A CMP can be internally validated in two different ways, namely:
(a) In a stepwise process involving validation of the analytical aspects at the
second, third and fourth level in Fig. 4.19; while this is labour-intensive and
time-consuming, it occasionally provides valuable specific information
about the particular instrument, sampling schedule, data, etc.
(b) By checking the CMP as a whole.
On the other hand, a CMP is externally validated by checking for consistency
between the results it produces and the information initially required.
A detailed description of validation procedures, of increasing use in the analytical chemical field, is beyond the scope of this introductory book on Analytical Chemistry. Note, however, that all validation processes share the need for