DIRECT ANALYSIS OF MILK FOR ALUMINUM USING ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

This work was conducted in order to develop a sensitive, precise metho d for the direct determination of aluminium in dairy products without sample pre-treatment. For this purpose, various chemical modifiers and thermal programmes for an electrothermal atomic absorption spectromet er were assessed. Different dry and wet sample pre-treatments were inv estigated in order to test the applicability of the method to the dire ct determination of aluminium in the matrices. Aluminium adsorption or leaching in various milk storage materials was also investigated. The proposed method allows the determination of aluminium in the range 5- 50 mu g l(-1) and a detection limit of 0.32 mu g l(-1) for aluminium. The precision achieved, expressed as the relative standard deviation, was 5.6% for within-run assays (repeatability) and 12.7% for between-r un assays (reproducibility). Various,types of commercially available m ilk (skim, low fat and whole) and milkshake (marketed in different pac kages) were analysed after dilution to 1 + 3 (v/v) with 0.2% HNO3. Pro cessing whole milk for drinking slightly decreases its aluminium conte nt, but heating in aluminium vessels also slightly increases its conte nt. The reliability of the entire procedure was confirmed by an analys is performed on a Standard Reference Material.