Common Analytical Problems
We indicated that analytical chemistry is more than a collection of qualitative and quantitative methods of analysis.
Nevertheless, many problems
on which analytical chemists
work ultimately involve
either a qualitative or quantita- tive measurement. Other problems may involve characterizing a sample’s chemical or physical properties. Finally,
many analytical chemists engage in fundamental studies of analytical methods.
In this section we briefly
discuss each of these four areas of analysis.
Many problems in analytical chemistry begin with the need to identify
what is present in a sample.
This is the
scope of a qualitative analysis, examples of which
include identifying the
products of a chemical reaction, screening an athlete’s urine for the presence
of a performance-enhancing drug, or determining the spatial dis- tribution of Pb on the surface
of an airborne particulate. Much
of the early
work in analytical chemistry involved the development of simple chemical
tests to identify the presence of inorganic
ions and organic
functional groups. The classical labora- tory courses in inorganic and organic qualitative analysis,9 still taught
at some schools, are based on this work.
Currently, most qualitative analyses use methods such as infrared spectroscopy, nuclear magnetic resonance, and mass spectrometry. These qualitative applications of identifying organic and inorganic
compounds are covered adequately elsewhere in the
undergraduate curriculum and,
so, will receive no further consideration in this text.
Perhaps the most common type of problem
encountered in the analytical lab is
a quantitative analysis. Examples of typical quantitative analyses include the ele-
mental analysis of a newly synthesized compound,
measuring the concentration of glucose in blood,
or determining the difference between
the bulk and surface con- centrations of Cr in steel. Much of the analytical work in clinical, pharmaceutical, environmental,
and industrial labs involves developing new methods for determin-
ing the concentration of targeted
species in complex
samples. Most of the examples in this text come from the area of quantitative analysis.
Another important area of analytical chemistry, which receives
some attention in this text, is the development of new methods
for characterizing physical
and chemical properties. Determinations of chemical structure, equilibrium constants,
particle size, and
surface structure are
examples of a characterization analysis.
purpose of a qualitative, quantitative, and characterization analysis
is to solve a problem associated with a sample.
A fundamental analysis, on
the other hand, is directed toward
improving the experimental methods used in the other areas of analytical
chemistry. Extending and improving
the theory on which a method
is based, studying
a method’s limitations, and designing new and modify- ing old methods are
examples of fundamental studies in analytical chemistry.