1.6 Conceptual and Technical Hierarchies
27
Box 1.11
Quantity
Measurand
I Analyte
It is interesting to distinguish the following three terms, which can be ranked with respect to
one another:
Quantity: An attribute of a phenomenon, object or substance that can be distinguished
qualitatively and determined quantitatively.
Measurand: A quantity that is measured via a comparison that provides the required information.lt is equivalent to quantity in the physical domain.
Analyte:
A chemical species (element, ion, molecule, radical) that can be identified (and
its amount or concentration determined) via a chemical measurement process.
It is a special type of measurand in chemical metrology.
Quantity and measurand not always coincide in the analytical chemical domain. Thus, the
signal (quantity) provided by most instruments is of the electrical type (volts or amperes);
what one actually wants to measure, however, is the measurand (e. g. the absorbance, in a UVvisible molecular absorption spectrophotometer).
All analytes can be considered measurands; however, most measurands. but not all. are
analytes. One case in point is the pH (a measurand) provided by a glass electrode. which is
sensitive to the concentration of protons (analytes); the potentiometer measures the
potential difference between the glass electrode and a reference electrode.
Box 1.12
The ranking on the left of Fig. 1.18 is materialized here in various representative examples.
Problem
I
( Example 1 ) Contamination of a
river
( Example 2 ) Drug abuse at the
olympic games
( Example 3 ) Adulteration of olive
oil with extraneous
fat
( Example 4 ) Toxicity of yellowpainted toys
(cadmium paint)
( Example 5 ) Economic feasibility
of gold recovery
from mining waste
I Object
The fiver. with its
geographic and
temporal features
Athletes
Factory output
Toys from an imported batch
The waste dump as a
whole
Sample(s) I
Aliquots of the
object collected at
different places and
times
Urine
Aliquots
representative
of the output
Surface scrapmgs
from various toys
selected according
to sampling plan
Samples of the
Ob~ect collected at
di erent depths at
different places
Analytes
OrgaOic and
100'ganic
COnlamon311ng
lpe('el
Amphelam nel.
hormones.
~ blockers. elc
Vege able and
anima fa!
God
27
Box 1.11
Quantity
Measurand
I Analyte
It is interesting to distinguish the following three terms, which can be ranked with respect to
one another:
Quantity: An attribute of a phenomenon, object or substance that can be distinguished
qualitatively and determined quantitatively.
Measurand: A quantity that is measured via a comparison that provides the required information.lt is equivalent to quantity in the physical domain.
Analyte:
A chemical species (element, ion, molecule, radical) that can be identified (and
its amount or concentration determined) via a chemical measurement process.
It is a special type of measurand in chemical metrology.
Quantity and measurand not always coincide in the analytical chemical domain. Thus, the
signal (quantity) provided by most instruments is of the electrical type (volts or amperes);
what one actually wants to measure, however, is the measurand (e. g. the absorbance, in a UVvisible molecular absorption spectrophotometer).
All analytes can be considered measurands; however, most measurands. but not all. are
analytes. One case in point is the pH (a measurand) provided by a glass electrode. which is
sensitive to the concentration of protons (analytes); the potentiometer measures the
potential difference between the glass electrode and a reference electrode.
Box 1.12
The ranking on the left of Fig. 1.18 is materialized here in various representative examples.
Problem
I
( Example 1 ) Contamination of a
river
( Example 2 ) Drug abuse at the
olympic games
( Example 3 ) Adulteration of olive
oil with extraneous
fat
( Example 4 ) Toxicity of yellowpainted toys
(cadmium paint)
( Example 5 ) Economic feasibility
of gold recovery
from mining waste
I Object
The fiver. with its
geographic and
temporal features
Athletes
Factory output
Toys from an imported batch
The waste dump as a
whole
Sample(s) I
Aliquots of the
object collected at
different places and
times
Urine
Aliquots
representative
of the output
Surface scrapmgs
from various toys
selected according
to sampling plan
Samples of the
Ob~ect collected at
di erent depths at
different places
Analytes
OrgaOic and
100'ganic
COnlamon311ng
lpe('el
Amphelam nel.
hormones.
~ blockers. elc
Vege able and
anima fa!
God