1.5 Evolution of Analytical Chemistry
21
The basic principles of classical Analytical Chemistry were essentially
thermodynamic, with some kinetic connotations; at present, however, kinetics is
akin to thermodynamics in importance {Fig.1.14.2}. In classical Analytical
Chemistry, chemical kinetics was virtually the sole type of kinetics considered,
either to circumvent its adverse effects in slow reactions or to exploit them {e.g.
to develop kinetic methods of analysis}. Currently, physico-chemical and purely
physical kinetics also play prominent roles: introducing the time dimension has
enabled the development of major analytical chemical techniques such as picosecond spectroscopy and time-domain electroanalytical modes, among others
{Fig.1.14.2}.
Materials, reactions and analytes, which used to be mostly inorganic in the
classical period, are now varied in nature, as seen in analysing the definition of
Analytical Chemistry {Fig. 1.14.3}. Tools have also evolved from primarily chemical to widely variable in nature {Fig. 1.14.4}.
The minimum amounts or concentrations required for analytes to be identified and quantified (i. e. limits of detection) have also changed dramatically:
from the gram/mole level to others several orders of magnitude lower {Fig.
1.14.5}. As the potential of Analytical Chemistry has been expanded with new
tools and processes, the number of analytes that can be determined in a straightforward, convenient way in a single sample has also risen dramatically {Fig.
1.14.6}.
The aims of analytical determinations have also changed markedly in
response to the ever increasing demand for information {Fig. 1.14.7}. Thus, the
overall content in a given analyte can easily be inadequate for the intended
purpose; often, one needs to know not only the forms in which the analyte may
be present in the unknown sample or system, but also their relative proportions.
So-called "speciation" is a key to Environmental Analytical Chemistry, but is also
significant to determinations in other fields such as Clinical Chemistry {e. g.
ionic and total calcium, free and HD L cholesterol}, Food Chemistry (e. g. free and
bound sulphur dioxide in wine) and Pharmaceutical Chemistry (e.g. enantiomer proportions in an active principle). For solid materials, one must also know
the spatial distribution of the composition and the structure. The dimensions of
analytical information have also expanded dramatically {Fig.1.14.8}. Thus,
gravimetry and titrimetry provide one-dimensional information [F = f(x}],
whereas conventional analytical techniques {e.g. UV-visible spectroscopy,
chromatography} produce two-dimensional information of two types, viz.
F = f(x,y} and F = f(x, t}, where x is the measured signal, y an instrumental
variable and t time. Three-dimensional information is becoming increasingly
affordable and multi-dimensional data is bound to become available in the very
near future.
The evolution of each facet of Analytical Chemistry can be used as the
starting point to assess the global change undergone by this science and anticipate its future.
21
The basic principles of classical Analytical Chemistry were essentially
thermodynamic, with some kinetic connotations; at present, however, kinetics is
akin to thermodynamics in importance {Fig.1.14.2}. In classical Analytical
Chemistry, chemical kinetics was virtually the sole type of kinetics considered,
either to circumvent its adverse effects in slow reactions or to exploit them {e.g.
to develop kinetic methods of analysis}. Currently, physico-chemical and purely
physical kinetics also play prominent roles: introducing the time dimension has
enabled the development of major analytical chemical techniques such as picosecond spectroscopy and time-domain electroanalytical modes, among others
{Fig.1.14.2}.
Materials, reactions and analytes, which used to be mostly inorganic in the
classical period, are now varied in nature, as seen in analysing the definition of
Analytical Chemistry {Fig. 1.14.3}. Tools have also evolved from primarily chemical to widely variable in nature {Fig. 1.14.4}.
The minimum amounts or concentrations required for analytes to be identified and quantified (i. e. limits of detection) have also changed dramatically:
from the gram/mole level to others several orders of magnitude lower {Fig.
1.14.5}. As the potential of Analytical Chemistry has been expanded with new
tools and processes, the number of analytes that can be determined in a straightforward, convenient way in a single sample has also risen dramatically {Fig.
1.14.6}.
The aims of analytical determinations have also changed markedly in
response to the ever increasing demand for information {Fig. 1.14.7}. Thus, the
overall content in a given analyte can easily be inadequate for the intended
purpose; often, one needs to know not only the forms in which the analyte may
be present in the unknown sample or system, but also their relative proportions.
So-called "speciation" is a key to Environmental Analytical Chemistry, but is also
significant to determinations in other fields such as Clinical Chemistry {e. g.
ionic and total calcium, free and HD L cholesterol}, Food Chemistry (e. g. free and
bound sulphur dioxide in wine) and Pharmaceutical Chemistry (e.g. enantiomer proportions in an active principle). For solid materials, one must also know
the spatial distribution of the composition and the structure. The dimensions of
analytical information have also expanded dramatically {Fig.1.14.8}. Thus,
gravimetry and titrimetry provide one-dimensional information [F = f(x}],
whereas conventional analytical techniques {e.g. UV-visible spectroscopy,
chromatography} produce two-dimensional information of two types, viz.
F = f(x,y} and F = f(x, t}, where x is the measured signal, y an instrumental
variable and t time. Three-dimensional information is becoming increasingly
affordable and multi-dimensional data is bound to become available in the very
near future.
The evolution of each facet of Analytical Chemistry can be used as the
starting point to assess the global change undergone by this science and anticipate its future.