Chemistry Reference
In-Depth Information
Graphite
furnace
/
Flame
CCD detector
Échelle
grating
Prism
Xe
lamp
Figure 11.3
Instrumental setup of a high-resolution continuum source atomic absorption spectrometer.
(b) HR-CS GFAAS offers superior background correction potential. In the first place, this technique allows
monitoring the spectral neighborhood of the analyte lines, thus permitting to detect potential interferences.
In the case that these interferences cannot be resolved in time (by optimization of the temperature
program combined with the use of chemical modifiers), the technique still offers a considerably superior
approach for the correction of complex, high and even rapidly changing backgrounds, since they are
monitored simultaneously with the atomic absorption lines [66].
(c) It is possible to decrease the sensitivity and therefore expand the working range by measuring the
absorbance at the wings of absorption lines [67].
(d) It opens the doors to monitoring low levels of non-metals, such as Cl, F, P or S, for which using narrow
molecular absorption 'lines' may be an appealing alternative since the most sensitive atomic lines for
these elements are situated in the far UV region, which is not accessible for LS-AAS instrumentation [68].
(e) Even though the spectral bandwidth that is simultaneously monitored is very narrow (approx.
0.2-0.3 nm in the UV region and up to 0.5 nm in the visible region), there is still some potential to carry
out multi-element monitoring either simultaneously (if the elements shows atomic lines that are very
close) or sequentially, by means of a multiple atomization temperature program [69].
From the point of view of Green Analytical Chemistry, these advantages can be considered as very relevant,
since they become really useful when the goal is to develop methods for the direct analysis of solid samples
and other complex materials (e.g., oils). Indeed, for these challenging applications, being capable of detecting
lower analyte contents, correcting the background in a more efficient way and achieving some flexibility with
regard to the sensitivity (it has to be remembered that when the goal is to directly analyze a solid material it
is not very simple to dilute the sample), are all key benefits. Multi-element analysis is obviously another
important advantage, as discussed before.
However, a conceptual change is also possible according to (d). In fact, the use of the high-resolution
continuum source technique is not only restricted to the monitoring of atomic absorption, but also molecular
lines can be detected and quantified. This is of immediate importance to detect elements that could hardly be
measured before by means of GFAAS, such as Cl, F or S. It makes also feasible to detect molecular species as
an alternative to the production of atoms, which is a process that typically requires more temperature (meaning
