Chelatometric titration of iron, zinc and aluminium involving masking and demasking with acetylacetone
A stepwise complexometric method with EDTA has been developed for the determination of iron, zinc and aluminium in a single aliquot solution involving direct titration of iron(III)-acetylacetonate at pH 3.0 using acetylacetone as an auto-indicator. Zinc is determined in the same solution by direct titration with EDTA raising pH to 5.3 using xylenol orange as indicator, while aluminium being masked with acetylacetone at room temperature (25 ± 5°). However, aluminium is determined in the same solution indirectly with EDTA at pH 5.3 using xylenol orange as indicator after demasking aluminium from aluminium acetylacetonate at 90° and formation of Al-EDTA complex. Alternatively, aluminium may be determined by adding NaF and titrating released EDTA with zinc acetate solution. Interferences due to titanium, zirconium, manganese, nickel, cobalt, copper and chromium have been eliminated by complexing them with different ligands. The method has been standardised against synthetic solutions and applied to various enamel and frit samples.