| Popis: |
Aluminium was determined in a flow-injection system involving the formation of the aluminium(III)-1,2-dihydroxyanthraquinone-3-sulphonic acid (DASA) complex at pH 9.0 and amperometric measurement of excess of DASA at +0.50 V on a gold electrode. Electrode fouling by adsorption of DASA oxidation products was minimized by the use of a double pumping system to provide a reagent cycle and a wash cycle. During the wash cycle the gold electrode surface was reactivated electrochemically by cathodic-anodic voltage cycling. The linear working range was governed by the DASA concentration. For 2× 10−5, 5 × 10−5 and 5 × 10−4 M DASA the linear ranges were (0.05–1.0)× 10−5, (0.1–2.2) × 10−5 and (0.1–1.2) × 10−4 M Al(III), respectively. The detection limit when using 2 × 10−5 M DASA was 2.5 × 10−7 M Al(III) and the R.S.D. for 9 × 10−6 M Al(III) was 4.3% (n = 6). Nitrilotriacetic acid, tannins and Fe(III) interfered; no interference was observed with F−, PO3−4, citric, oxalic and fulvic acids, Mg2+ or Ca2+. The method was applied to the determination of Al(III) in soil extracts. |
