1.2 Analytical Chemical Information
9
Box 1.4
On arrival at the laboratory, a rock may have a silica (Si0 2 ) content from 0 to 100% (the
highest possible uncertainty). By analysis, the laboratory obtains a silica content of, say, 78.3 ±
0.1 %; as a result, the rock can be said to contain from 78.2 to 78.4 % silica and the uncertainty
will have been substantially diminished.The specific uncertainty for the sample (i.e. the range
over which the true result can be expected to vary) will be ± 0.1 % .
ot knowing whether bay water is polluted with mercury species also represents the
highest possible uncertainty, which can be reduced by using a qualitative test to obtain a yes/no
response and, to an even higher degree, by quantifying the total concentration of mercury. If, in
addition to confirming the presence of mercury and determining its concentration, one
distinguishes among specific mercury species (e.g. the metal ion in free form and as a part of
chelates or organometallic compounds), the initial uncertai nty will be further decreased.
Mercury contamination
Presence of mercury
Total concentration of mercury
Presence of various
mercury species
Discriminate concentrat ions
of mercury species
Materials possess intrinsic information that persists or changes in space and/
or time; ideally, this is the type of information to be supplied by the analytical chemist. This intrinsic information is subject to no uncertainty,
represents the top level of analytical quality and is characterized via an ideal,
unattainable property: trueness (see Fig. 1.6). At a lower level is referential information, which is factual, reasonably accurate - nearly as much as intrinsic
information - and scarcely uncertain. This type of information is obtained
under uncommon conditions (e.g. in intercomparison tests involving many
participating laboratories using different analytical processes) and is basically
used as a reference to extract ordinary analytical information or assess its
goodness. This last type of information is on the lowest step of the quality
hierarchy; it is also based on facts but is less accurate and more uncertain than
referential information.
The way analytical information is conveyed strongly affects its quality, which
may diminish or even be lost altogether in the way. Analytical chemists can
deliver analytical information by establishing one- or two-way links with the following (Fig. 1.7):
(1) Society, other scientific and technical areas, and the departments of the body
to which they are answerable (the one that requested the analytical information in the first place);
9
Box 1.4
On arrival at the laboratory, a rock may have a silica (Si0 2 ) content from 0 to 100% (the
highest possible uncertainty). By analysis, the laboratory obtains a silica content of, say, 78.3 ±
0.1 %; as a result, the rock can be said to contain from 78.2 to 78.4 % silica and the uncertainty
will have been substantially diminished.The specific uncertainty for the sample (i.e. the range
over which the true result can be expected to vary) will be ± 0.1 % .
ot knowing whether bay water is polluted with mercury species also represents the
highest possible uncertainty, which can be reduced by using a qualitative test to obtain a yes/no
response and, to an even higher degree, by quantifying the total concentration of mercury. If, in
addition to confirming the presence of mercury and determining its concentration, one
distinguishes among specific mercury species (e.g. the metal ion in free form and as a part of
chelates or organometallic compounds), the initial uncertai nty will be further decreased.
Mercury contamination
Presence of mercury
Total concentration of mercury
Presence of various
mercury species
Discriminate concentrat ions
of mercury species
Materials possess intrinsic information that persists or changes in space and/
or time; ideally, this is the type of information to be supplied by the analytical chemist. This intrinsic information is subject to no uncertainty,
represents the top level of analytical quality and is characterized via an ideal,
unattainable property: trueness (see Fig. 1.6). At a lower level is referential information, which is factual, reasonably accurate - nearly as much as intrinsic
information - and scarcely uncertain. This type of information is obtained
under uncommon conditions (e.g. in intercomparison tests involving many
participating laboratories using different analytical processes) and is basically
used as a reference to extract ordinary analytical information or assess its
goodness. This last type of information is on the lowest step of the quality
hierarchy; it is also based on facts but is less accurate and more uncertain than
referential information.
The way analytical information is conveyed strongly affects its quality, which
may diminish or even be lost altogether in the way. Analytical chemists can
deliver analytical information by establishing one- or two-way links with the following (Fig. 1.7):
(1) Society, other scientific and technical areas, and the departments of the body
to which they are answerable (the one that requested the analytical information in the first place);