6.3 Types of Reference Materials
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– Physico-chemical RMs for which properties such as density, viscosity and pH are
certified (such materials are used for the calibration of measuring instruments,
e.g., viscometers, pH meters).
– Materials with the assigned value of certain properties expressed in arbitrary units
(e.g., fuel with the appropriate Research Octane Number (RON) or Motor Octane
Number (MON); both numbers are evaluated with the same measurement process,
the differences arise from the conditions used during the measurements).
6.4 Chemical Substances of a Given Purity
Substances of known chemical composition, its purity and available information on
impurity content are primarily used for the calibration of measuring instruments and
to identify the presence of the given substance in the test object. In practice, they are
available as solids (in the form of a powder or compact solid) as gases (pure gas or
gases mixture) or as liquids (prepared gravimetrically by weight a pure substance in
a given volume of solvent). The uncertainty associated with the value describing the
purity affects (it is a component of the budget uncertainty) the value of the overall
uncertainty for the measurement procedure.
The chemical substances of high purity are also used to create the matrix composition corresponding to samples of the known main components. It is required
however that the high purity substance do not contained the analyte (meaning that
the analyte is below the detection limit of the used measuring technique).
6.5 Matrix Reference Materials
Materials prepared with the use of natural matters, such as soil, blood, leaves of plants,
tissues of living organisms, dust, food products; these are just a few examples from a
very extensive list of objects taken from nature. In terms of chemical measurements,
matrix materials play an extremely important role, especially due to the fact that they
behave chemically and physically the same as the respective test sample, assuming
their identity or closeness to the chemical composition and physical properties of the
investigated objects (samples). Matrix RMs should undergo processing that ensures
their expected homogeneity and stability.
6.6 Applicability of Reference Materials
RMs may be used for different purposes. Those without certified values may be used
to evaluate the precision of the measurements and in the quality control. Those RMs
with certified values may be used, among other things, in:
73
– Physico-chemical RMs for which properties such as density, viscosity and pH are
certified (such materials are used for the calibration of measuring instruments,
e.g., viscometers, pH meters).
– Materials with the assigned value of certain properties expressed in arbitrary units
(e.g., fuel with the appropriate Research Octane Number (RON) or Motor Octane
Number (MON); both numbers are evaluated with the same measurement process,
the differences arise from the conditions used during the measurements).
6.4 Chemical Substances of a Given Purity
Substances of known chemical composition, its purity and available information on
impurity content are primarily used for the calibration of measuring instruments and
to identify the presence of the given substance in the test object. In practice, they are
available as solids (in the form of a powder or compact solid) as gases (pure gas or
gases mixture) or as liquids (prepared gravimetrically by weight a pure substance in
a given volume of solvent). The uncertainty associated with the value describing the
purity affects (it is a component of the budget uncertainty) the value of the overall
uncertainty for the measurement procedure.
The chemical substances of high purity are also used to create the matrix composition corresponding to samples of the known main components. It is required
however that the high purity substance do not contained the analyte (meaning that
the analyte is below the detection limit of the used measuring technique).
6.5 Matrix Reference Materials
Materials prepared with the use of natural matters, such as soil, blood, leaves of plants,
tissues of living organisms, dust, food products; these are just a few examples from a
very extensive list of objects taken from nature. In terms of chemical measurements,
matrix materials play an extremely important role, especially due to the fact that they
behave chemically and physically the same as the respective test sample, assuming
their identity or closeness to the chemical composition and physical properties of the
investigated objects (samples). Matrix RMs should undergo processing that ensures
their expected homogeneity and stability.
6.6 Applicability of Reference Materials
RMs may be used for different purposes. Those without certified values may be used
to evaluate the precision of the measurements and in the quality control. Those RMs
with certified values may be used, among other things, in: