Page 50 - An Introduction to Analytical Atomic Spectrometry - L. Ebdon
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Figure 2.11
Cutaway diagram to show the profile of a
single-slot burner with raised edges.
are formed over each opening. During design, the number of holes, their size and conductivity of the
metal must be considered. Such burners are best suited to flames of low burning velocity, and this
design still forms the basis for flames used in atomic fluorescence spectroscopy.
Slot burners are now far more popular. Slots of 100 mm are popular for atomic absorption
spectrometry using air-acetylene but, because of the higher burning velocity of nitrous oxide-acetylene,
such a long slot is not safe and one of 50 mm is used. The width of the slot, its length and the
conductivity of the metal used (commonly aluminium, stainless steel or titanium) are important. The
narrower is the slot, the greater are the cooling and stability. However, the tendency to clog is increased.
Three-slot (or Boling) burners, with three parallel slots, are also available. A profile of a well designed
single-slot burner is shown in Fig. 2.11. The raised edges at the slot help to prevent carbon build-up; the
curvature at the base helps to avoid turbulence.
Q. Why is the slot used for a nitrous oxide-acetylene burner shorter than that used for an air-acetylene
burner?
Q. How is it possible to redesign a slot burner to take up to 40% dissolved solids (cf. the normally
acceptable 4-6%) when using a highly conductive material for the burner head?
2.2.5 Spectrometers
Modern instruments use gratings rather than prisms for dispersion; Czerny-Turner and Ebert systems
are commonly employed (see Section 4.4.5).
