Bernhard Welz
Federal University of Santa Catarina, Brazil
Title: High-temperature high-resolution molecular absorption spectrometry – a supplementary technique to ICP-MS for the determination of halogens.
Biography
Biography: Bernhard Welz
Abstract
Inductively coupled plasma mass spectrometry (ICP-MS) is without doubt one of the most sensitive techniques for the determination of trace elements in a variety of matrices. However, there are also some limitations, and the most serious ones are with the determination of the halogens. Fluorine, which has an ionization energy of 17.42 eV, can essentially not be determined by ICP-MS, as the ionization energy of the plasma gas argon is only 15.76 eV. Chlorine and bromine have lower ionization energies of 12.97 eV and 11.81 eV, respectively, and can be determined by ICP-MS; however, severe matrix and memory effects can often be observed when conventional sample introduction with a nebulizer/spray chamber is used. One way out of this problem is using electrothermal vaporization (ETV) for sample introduction. High-temperature high-resolution molecular absorption spectrometry (HR-CS MAS) is ideally suited for the determination of non-metals, and can therefore be used as a supplementary technique to ICP-MS. The sample – in many cases a solid sample – is directly introduced into a small graphite tube furnace, a ‘molecule-forming reagent’ is added, and the furnace is heated to a previously optimized temperature – typically between 1500 °C and 2500 °C. At this temperature, diatomic molecules are formed in the gas phase, such as CaF, SrCl or CaBr, which exhibit a characteristic absorption spectrum, which can be used for the sensitive determination of these halogens. Plant materials, coal, copper concentrate, cosmetics and fish oil were investigated with this technique and the results compared with those of ICP-MS where possible.