Editing Atomic absorption spectroscopy (section)

==== Electrothermal atomizers ====
[[File:GFAA method development-courtesy jball-Analytik Jena USA.JPG|thumb|right |400 px|GFAA method development]]
[[File:Lvov furnace 2.JPG|thumb|right|Graphite tube]]

[[Graphite furnace atomic absorption|Electrothermal AAS]] (ET AAS) using graphite tube atomizers was pioneered by Boris V. L'vov at the [[Saint Petersburg Polytechnical University|Saint Petersburg Polytechnical Institute]], Russia,<ref>{{cite journal |last1=L'vov |first1=Boris |title=Recent advances in absolute analysis by graphite furnace atomic absorption spectrometry |date=1990 |journal=Spectrochimica Acta Part B: Atomic Spectroscopy |doi=10.1016/0584-8547(90)80046-L |volume=45 |issue=7 |pages=633–655 |url=https://pubs.rsc.org/en/Content/ArticleLanding/1988/JA/JA9880300009|bibcode=1990AcSpB..45..633L |url-access=subscription }}</ref> since the late 1950s, and investigated in parallel by Hans Massmann at the Institute of Spectrochemistry and Applied Spectroscopy (ISAS) in Dortmund, Germany.<ref>{{cite web|title=Analytical Methods for Graphite Tube Atomizers|url=http://hpst.cz/sites/default/files/attachments/gta-analytical-methods-0848.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://hpst.cz/sites/default/files/attachments/gta-analytical-methods-0848.pdf |archive-date=2022-10-09 |url-status=live|website=agilent.com|publisher=Agilent Technologies}}</ref>

Although a wide variety of graphite tube designs have been used over the years, the dimensions nowadays are typically 20–25&nbsp;mm in length and 5–6&nbsp;mm inner diameter. With this technique liquid/dissolved, solid, and gaseous samples may be analyzed directly. A measured volume (typically 10–50&nbsp;μL) or a weighed mass (typically around 1&nbsp;mg) of a solid sample are introduced into the graphite tube and subject to a temperature program. This typically consists of stages, such as drying – the solvent is evaporated; [[pyrolysis]] – the majority of the matrix constituents are removed; atomization – the analyte element is released to the gaseous phase; and cleaning – eventual residues in the graphite tube are removed at high temperature.<ref>{{Cite web|title=Atomic Spectroscopy - GF-AAS|url=https://sites.chem.utoronto.ca/chemistry/coursenotes/analsci/atomic/gfaas.html#:~:text=Graphite%20furnace%20atomization%20(also%20known,inside%20a%20hollow%20graphite%20tube.|access-date=2021-03-08|website=sites.chem.utoronto.ca}}</ref>

The graphite tubes are heated via their ohmic resistance using a low-voltage high-current power supply; the temperature in the individual stages can be controlled very closely, and temperature ramps between the individual stages facilitate the separation of sample components. Tubes may be heated transversely or longitudinally, where the former ones have the advantage of a more homogeneous temperature distribution over their length. The so-called stabilized temperature platform furnace (STPF) concept, proposed by Walter Slavin, based on research of Boris L'vov, makes ET AAS essentially free from interference.{{citation needed|date=July 2014}} The major components of this concept are atomization of the sample from a graphite platform inserted into the graphite tube (L'vov platform) instead of from the tube wall in order to delay atomization until the gas phase in the atomizer has reached a stable temperature; use of a chemical modifier in order to stabilize the analyte to a pyrolysis temperature that is sufficient to remove the majority of the matrix components; and integration of the absorbance over the time of the transient absorption signal instead of using peak height absorbance for quantification.

In ET AAS, a transient signal is generated, the area of which is directly proportional to the mass of analyte (not its concentration) introduced into the graphite tube. This technique has the advantage that any kind of sample, solid, liquid, or gaseous, can be analyzed directly. Its sensitivity is 2–3 orders of magnitude higher than that of flame AAS, so that determinations in the low μg L<sup>−1</sup> range (for a typical sample volume of 20&nbsp;μL) and ng g<sup>−1</sup> range (for a typical sample mass of 1&nbsp;mg) can be carried out. It shows a very high degree of freedom from interferences, so that ET AAS might be considered the most robust technique available nowadays for the determination of trace elements in complex matrices.{{citation needed|date=July 2014}}