Analytical method development and validation for Aluminium

Abstract

Aluminium comprises about 8% of earth's crust so there is possibility that aluminium can contaminate the natural resources, with references to previous researches on determination of aluminium, we developed a simple, rapid, and economic colorimetric method for the detection of aluminium from various sources. Aluminium has an electric charge and a small ionic radius of about 0.51Å, conferring upon it strong polarizing capabilities. Standard reduction potential for reacting Al⁺³ is -1.67 V. This high electronegativity makes aluminium highly reactive. 8-hydroxyquinoline-5-sulphonic acid has been used for chelation and subsequent determination of aluminium content from samples. It is a light-yellow coloured compound and is a derivative of heterocyclic quinoline substituted with the hydroxyl group on carbon number 8 and sulphonic acid group at carbon number 5. Sulfonic acid improves the solubility of the molecule and of the corresponding fluorescent complexes in polar solvents. Aluminium readily complexes with 8-hydroxyquinoline-5-sulphonic acid in acidic buffer and remains stable for 30 mins. The maximum absorbance of aluminium and 8-hydroxyquinoline-5-sulphonic acid complex was determined using UV spectro-photometry at 359 nm. Concentration of aluminium in the sample was found to be linear within the range of 1.2-2.8 mM with acceptable precision and accuracy, as per guidelines. The developed method was validated according to ICH (Q2R1) guidelines. The developed method was used to assess the aluminium content in a marketed antacid formulation. The recovered aluminium content was within the industrial acceptance limit. The developed method is thus effective for accurate determination of aluminium from marketed samples.