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DETERMINATION ALUMINUM TOTAL
Colourimetry
A sample is filtered in the field through a 0.45 µm membrane filter and preserved with diluted mineral acid. A hydroxylamine hydrochloride (NH2OH.HCl) solution, containing BeSO4 (to minimize the interference of fluoride), is added to two aliquots: one is the test aliquot and the other is the colour correction aliquot. A solution, containing ferron and orthophenanthroline (9, 10-phenanthroline) (to minimize the interference of iron), is added to one of the sample aliquots. Sodium acetate solution is added to both sample aliquots. The absorbance of the aliquot, containing ferron/orthophenanthroline, is measured spectrometrically at 520 nm, and compared to identically-prepared Al standard and blank solutions. A colour correction is made, using the aliquot without ferron and orthophenanthroline. The Al concentration measured is corrected for Fe, Mn and F ions, by the following equation:
mg/L Al = A – B – C + D where,
A = apparent mg/L Al
B = (0.12 x mg/L Fe)
C = 0.04 x mg/L Mn)
D = (0.05 x mg/L F)
The method detection limit is 0.01 mg/L.
Ferron/phenanthroline
7-iodo-8-hydroxyquinoline-5-sulphonic acid/C12H8N2
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http://www.minsocam.org/ammin/AM65/AM65_1249.pdf và Colloids and surfaces. A, Physicochemical and engineering aspects 2005, vol. 260, no 1-3, pp. 109-117 [9 page(s) (article)] (23 ref.)