Aluminium determination in food matrices IUPAC check sample survey of analytical performance

Aluminum has been determined by 24 laboratories in the context of a check sample survey. Samples studied were two duplicate diets, one of which was spiked with 15.87 mg Al/kg, and two blind duplicate milk powders. Target values for the duplicate diets were 11.80 and 27.90 mg Al/kg, respectively, and 15.65 mg Al/kg for the milk powders. Participants were requested to make only single determinations per sample. A two-step approach was used to assess the raw data. In the first step, those data were excluded that were outside a +/- 50% range of the duplicate diet spike and the target value for milk powder. Likewise, only one single data set per participant was accepted and results were ruled out stemming from procedures that have a detection limit of greater than 5 mg Al/kg. The remaining data were evaluated both statistically and in the context of the method performance parameters available. Best scores for aluminium were from laboratories applying wet-pressurized digestion in combination with electrothermal atomic absorption spectrometry. Results for laboratories applying dry-ashing for sample decomposition were unreliable. The overall performance for aluminium is very disappointing given the relatively high aluminium levels of the samples studied. Out of 24 laboratories 11 have one or more major problems with their aluminium determination. They should dramatically improve or replace their methodology for this element.