Figure 12.4
Gas chromatogram of the products obtained from n-hexane
when passed over a SiO 2 /Pt catalyst at 450°C. Column: 50 m^
× 0.32 mm PLOT, alumina modified with KCl. Temperature:
100 – 200 °C at 6°C min–^1. Carrier gas: Nitrogen.^
Identity of peaks: (1) propane (2) iso-butane (3) n-butane
(4) butene-1, butene-2 (5) iso-pentane (6) n-pentane
(7) 2-methyl- 1 - butene (8) 2-methyl pentane (9) 3-methyl pentane
(10) n-hexane (11) methyl cyclopentane (12) benzeneanalyte with minimum operator involvement. Moreover, the results obtained will frequently be more
reliable. An instrument neither suffers the tedium of repetitive work, nor does it make subjective
judgements of readings. Lastly, an automatic instrument can often be used in an environment where it is
impossible for an operator to work. Obvious examples are the inside of a nuclear reactor or the outside
of a spacecraft. Automated analysis may thus provide information more cheaply and reliably than
manual analysis as well as some data that would otherwise be unobtainable.
It is obvious that the simpler a method of analysis, the easier it will be to automate. Non-destructive
methods which involve a minimum of sample treatment are the most attractive. X-ray fluorescence, for
example, has been successfully applied to the continuous monitoring and control of process streams.
However, the scope of automated analysis is wide and methods have been designed with a basis in non-
specific properties (pH, conductance, viscosity, density) as well as those characteristic of the che-