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8 Modern Analytical Chemistry
qualitative analysis
An analysis in which we determine the include identifying the products of a chemical reaction, screening an athlete’s urine
identity of the constituent species in a for the presence of a performance-enhancing drug, or determining the spatial dis-
sample.
Nd in samples. Unfortunately, mass spectrometry is not a selective technique. A
mass spectrum provides information about the abundance of ions with a given
mass. It cannot distinguish, however, between different ions with the same mass.
Consequently, the choice of TIMS required developing a procedure for separating
the tracer from the aerosol particulates.
Validating the final experimental protocol was accomplished by running a
model study in which 148 Nd was released into the atmosphere from a 100-MW coal
utility boiler. Samples were collected at 13 locations, all of which were 20 km from
the source. Experimental results were compared with predictions determined by the
rate at which the tracer was released and the known dispersion of the emissions.
Finally, the development of this procedure did not occur in a single, linear pass
through the analytical approach. As research progressed, problems were encoun-
tered and modifications made, representing a cycle through steps 2, 3, and 4 of the
analytical approach.
Others have pointed out, with justification, that the analytical approach out-
lined here is not unique to analytical chemistry, but is common to any aspect of sci-
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ence involving analysis. Here, again, it helps to distinguish between a chemical
analysis and analytical chemistry. For other analytically oriented scientists, such as
physical chemists and physical organic chemists, the primary emphasis is on the
problem, with the results of an analysis supporting larger research goals involving
fundamental studies of chemical or physical processes. The essence of analytical
chemistry, however, is in the second, third, and fourth steps of the analytical ap-
proach. Besides supporting broader research goals by developing and validating an-
alytical methods, these methods also define the type and quality of information
available to other research scientists. In some cases, the success of an analytical
method may even suggest new research problems.
1C Common Analytical Problems
In Section 1A 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
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-
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tory courses in inorganic and organic qualitative analysis, 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.