THE ROLE OF THE

Traditional Role of the Chemist in the Automobile Plant Environment 13
most analysis performed in the lab by automotive chemists was classical. Around
this time, with the advent of electronics, equipment such as spectrophotometers
began to make its way into the automotive lab. I will later talk more about chromatography
because I believe it is an underutilized method in today’s automobile
lab. Chromatography is an instrumental analytical method used for separation and
resolution of materials such as coolants and additive packages in hydraulic fluids that
have closely related molecular structures. Distillation and extraction are classical
methods used in the laboratory as separation techniques. These methods, however,
are rarely used in today’s labs; they are mostly preparation techniques for some other
analytical method.
Depending on the sample and what type of analysis the chemist wants (qualitative
or quantitative), the chemist will then conduct the analysis and report the results.
2.3 metHods around metals
The primary components of automobiles are steel or aluminum, so one of the fastest
methods for analysis with the least amount of preparation of the sample is the
emissions spectrometer. From Table 2.1, we can see that a carbon sulfur analyzer,
such as a Leco, or atomic absorption spectrophotometer; scanning electron microscopy
(SEM); x-ray; and GC-MS are also used for this type of analysis. However,
an emissions spectrophotometer is most often used because of its lack of sample
preparation. Again, it is not our attempt here to go into great detail on each method.
Within an automotive analytical laboratory, however, speed is a priority so that a
material is identified and classified rapidly. An emissions spectrophotometer is such
an instrument.
2.3.1 Em i s s i o n spEc trophotom E tEr s
Generally, argon plasma sources have been used in this type of instrument since
the late 1970s. The argon plasma source has greater energetic excitation than the
atomic absorption discussed later. Electric arc and spark systems have been used in
labs since the 1930s. Their popularity within the auto industry was partially because
samples did not need to be prepared. Typical samples are prepared by simply grinding
away the surface finish. Care must be taken, however, to make sure there is a flat
area to rest on the sample stand of the spectrophotometer. Prior to analysis, the electrode
(graphite for aluminum samples and steel for steel samples) must be gapped to
the proper distance for analysis. Because of the higher energy involved, spectra for
dozens of elements can be recorded simultaneously [1]. The excitation source must
supply sufficient energy to vaporize the sample that is being analyzed. It must also
be able to cause electronic excitation in the sample.
We are attempting to isolate line spectra from excited atoms and measure the
intensity from these lines. To do this, we excite an element from the ground state to an
excited state. For instance, a single outer electron from metallic sodium occupies the
3 s orbital at ground state. An electric spark or arc is used to excite the electron into
a higher energy state. Upon return to the ground state, radiation is emitted at various
wavelengths. The sodium energy level diagram is listed in Figure 2.1 as an example.