Characterization of aluminum species with nitrate, perchlorate and sulfate ions in the positive and negative ion mode by electrospray ionization mass spectrometry

✍ Scribed by Tatsuya Urabe; Takahisa Tsugoshi; Miho Tanaka

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 206 KB
• Volume: 44
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.1485

✦ Synopsis

Abstract

The application of electrospray ionization mass spectrometry (ESI‐MS) for aluminum speciation in the positive and negative ion modes was discussed. Aluminum nitrate, perchlorate and sulfate solutions were measured by ESI‐MS. In the positive ion mode, aluminum species containing anions (Al‐L; L = NO~3~, ClO~4~ and SO~4~) were identified, while [Al(OH)~2~(H~2~O)~n~]^+^ (n = 2–4) were the main species. The affinity of the anions with Al^3+^ estimated by ESI‐MS was consistent with the hardness of the anions (hard and soft acids and bases principle) and the results from ^27^Al nuclear magnetic resonance studies. This indicates that the results observed from the positive ion mode preserved the chemical state of aluminum in the solution. In the negative ion mode, [Al(OH)~4−n~L~n~]^−^ (n = 0–2, L = NO~3~, ClO~4~) were the main species, which were considered to be converted from positive aluminum species, [Al(OH)(H~2~O)~n~]^+^ (n = 2–4), by the successive addition of anions. Anions did not only attach to one aluminum ion but also bridged two aluminum ions. In Al~2~(SO~4~)~3~ solution, the behavior of SO~4~^2−^ in the negative ion mode differed from that of NO~3~^−^ and ClO~4~^−^. This may reflect the affinity of SO~4~^2−^ with Al^3+^ in the solution or in the mass spectrometer or in both. Finally, detection mechanisms for the aluminum species in the solution are proposed for both the positive and negative ion modes. It is shown that ESI‐MS can be used to observe the interaction between Al^3+^ and anions. We show the importance of the interpretation of the results by ESI‐MS for obtaining new information of the metal species in the solution. Copyright © 2008 John Wiley & Sons, Ltd.