Page 80 - An Introduction to Analytical Atomic Spectrometry - L. Ebdon
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acid can be added to the sample and hydrogen chloride boiled off during atomization. Preferably, 50%
ammonium nitrate can be added (with care) to give the reaction
NaCl + NH NO 3 ® NaNO 3 + NH Cl
4
4
boils at decomposes decomposes sublimes
1413°C at 2100°C at 380°C at 335°C
The compounds of Group V elements are often volatile, and loss of, for example, arsenic, selenium
and tellurium during ashing of the sample can be reduced by the addition of nickel, to form nickel
arsenide. Such stabilization procedures are called matrix modification (see Section 3.6.4).
3.5.4.2 Anion and Cation Interferences.
Many of these have been reported, e.g. 0.1% v/v mineral acids interfere with several elements. While
some insights are being gained in terms of the theories discussed above, interferences are usually
combatted by matching standards and samples or by the method of standard additions.
3.5.4.3 Carbide Formation
The apparent slow atomization of some elements may be caused by carbide formation. Rapid heating
and a reproducible surface (e.g. a pyrolytic surface) help reduce this problem, as does coating of the
tube (e.g. with lanthanum, using lanthanum nitrate solution), and the use of metallic tubes or boats.
3.5.4.4 Condensation
Some interferences appear to be vapour-phase effects and are presumably due to occlusion of analyte
elements into particles of matrix. The use of platforms in furnaces (see Section 3.6.3), the use of
reactive purge gases (e.g. hydrogen) and dispersion of the matrix, e.g. by using an organic acid such
as ascorbic acid, can in some cases reduce such interferences.
Q. How can physical interferences be minimized?
Q. Is background correction more essential with flame or with electrothermal atomizers?
Q. How can interference from chloride ions be minimized?
