Anions in aqueous precipitation - Determination of Anions in Natural and Treated Waters - page 431

5.1.3.5 Mass spectrometric isotope dilution analysis
Mass spectrometric isotope dilution analysis has been applied to the determination of
chloride ion in rainfall and snow [4]. Detection limits of 1µg L −1 or lower can be
achieved by this technique. For the isotope ratio measurement of chlorine and bromine a
single focusing mass spectrometer (Varian MAT, type CH 5 -TH) with a double filament
ion source and a Faraday cup as a detector was used. The filaments consist of rhenium.
The best precision of the isotope ratio measurement is achieved when a solution of (Ag
(NH 3 ) 2 ) X (X − =Cl − , Br − ) is deposited on the evaporation filament and dried under a heat
lamp. In the ion source the temperature of the ionisation filament is increased stepwise up
to a temperature of 1850°C
Using samples amounts of 1µmol halide with natural isotope composition, ion
intensities are achieved on the Faraday cup in the range of 10 −11 -10 −10 A for 35Cl − and
in the range of 10 −11 -5×10 −11 for 79Br − .
5.1.3.6 Ion chromatography
Various workers [6-15] have discussed the application of this technique to the
determination of chloride in rain. The application of this technique is discussed under
multianion analysis in sections 5.1.14.3, 12.4.1 and 12.4.2.
5.1.3.7 High performance liquid chromatography
The application of this technique is discussed under multianion analysis in sections
13.1.3.1 and 13.1.3.3.
5.1.3.8 Ion exchange chromatography
The application of this technique is discussed under multianion analysis in section
13.3.2.1.
5.1.3.9 Gas chromatography
The application of this technique is discussed under multianion analysis in section
14.1.2.2.
5.1.4 Fluoride
5.1.4.1 Isotachoelectrophoresis
The application of this technique is discussed under multianion analysis in section
14.6.2.1.