Can the TNT890 Metals Prep Set be used to digest samples for aluminium analysis?

Dokument-ID

Dokument-ID TE1149

Veröffentlichungsdatum

Veröffentlichungsdatum 06.12.2018
Frage
Can the TNT890 Metals Prep Set be used to digest samples for aluminium analysis?
Zusammenfassung
Using TNT890 for aluminium
Antwort
The TNT890 is a kit to perform a persulfate digestion in an acidic solution (sulfuric acid), followed by a subsequent neutralization with sodium hydroxide solution.

Aluminium usually needs digestion, if the samples contain either insoluble Alumina Al2O3 or intermediates between Al2O3 and Al(OH)3 (so-called “oxihydrates”) or organic chelants.

Persulfate would more easily promote the formation of Al2O3 from non-oxidized Al3+ ions, and NaOH (e.g. a local excess) would promote the formation of Al(OH)3; both are just the opposite of what should be achieved in an aluminium digestion.

The most effective digestion for aluminium could be expected from hot nitric acid: it would destroy organic chelants and keep the Alumnium as the free Al3+  ion. Other than the TNT890, the excessive nitric acid could be removed by evaporation (until dryness of the sample; the remaining salt cake could then be dissolved by hot DI water), without a need to use NaOH for neutralization.

Therefore one would expect, that the TNT890, used for aluminium digestion, is less effective than an nitric acid digestion.

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