Direct analysis of coffee and tea for aluminium determination by electrothermal atomic absorption spectrometry

A method for direct analysis of tea and coffee samples by using electrothermal atomic absorption spectrometry is described. Coffee and tea from different sources were analyzed without digestion step. For slurry analyses the samples were ground, sieved at 105 mu m and then suspended in 0.2% v/v HNO3 and 10% v/v Triton X-100 medium. For liquid phase aluminium determination the samples were prepared in the same way and only the liquid is introduced directly into the graphite furnace. Calibration was performed by aqueous standards for both cases and the determinations were carried out in the linear range between 50 and 250 mu g L-1. The characteristic mass of aluminium and the detection limit were 45 pg and 2 mu g L-1, respectively. Using a typical 0.1% m/v coffee slurry sample, the relative standard deviation of measurements (n = 15) for repeatability was about 8.2%.