8-hydroxyquinoline aluminium complexes

Some authors claim that detection limits (DLs) of 5 mgL are easily obtainable [167] using the batch PCV detection method. However, it has been reported that daily DLs range between 5 and 10 mg L and that personnel who are highly acquainted with the method were needed to achieve DLs down to <10 mg L [168]. This poses a problem when the non-labile or monomeric organic fraction of aluminium to be measured is very small. Errors for Alni can become high, and, because the Driscoll method is a subtraction method, the uncertainty of the calculated Ali fraction (Alim—Alni) can become unacceptable. To increase the precision, sample throughput and practicality of the Driscoll method, several flow injection analysis (FIA) systems have been designed both for the PCV method [169,170] and for detection with a fluorimetric determination of the 8-hydroxyquinoline-5-sulfonic acid (8-HQS) aluminium complex in a micellar medium (cetyltri-methylammonium bromide, CTAB) [168,171]. 

H. 8-Hydroxyquinaldine (XI). The reactions of 8-hydroxyquinaldine are, in general, similar to 8-hydroxyquinoline described under (C) above, but unlike the latter it does not produce an insoluble complex with aluminium. In acetic acid-acetate solution precipitates are formed with bismuth, cadmium, copper, iron(II) and iron(III), chromium, manganese, nickel, silver, zinc, titanium (Ti02 + ), molybdate, tungstate, and vanadate. The same ions are precipitated in ammoniacal solution with the exception of molybdate, tungstate, and vanadate, but with the addition of lead, calcium, strontium, and magnesium aluminium is not precipitated, but tartrate must be added to prevent the separation of aluminium hydroxide. 

V.A. Montes, C. Li, R. Pohl, J. Shinar, and P. Anzenbacher Jr., Effective color tuning in organic light-emitting diodes based on Aluminium tris(5-aryl-8-hydroxyquinoline) complexes, Adv. Mater., 16 2001-2003 (2004). 

Deprotonation of 8-hydroxyquinoline gives the didentate ligand 12.38 which has a number of applications. For example, Al + may be extracted into organic solvents as the octahedral complex [Al(12.38)3] providing a weighable form of AP for the gravimetric analysis of aluminium. 

Various methods have evolved based on the complexation of monomeric aluminium species with 8-hydroxyquinoline (oxine) and the rapid extraction of the formed Al(oxinate)3 complex into organic solvents, e.g. chloroform [162], toluene [163] or methyl isobutyl ketone (MIBK) [164] detection of the aluminium content was accomplished by electrothermal atomic absorption spectrometry. 

Hydroxyquinoline is a chelating ligand (referred to as oxine) which forms insoluble complexes with a number of di- and trivalent metals. The oxinates of these metals contain 2 or 3 oxinate groups per metal ion. In the case of aluminium the complex has 3 chelating ligands. Complete precipitation takes place at pH values of 5-10. 

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