A fast and simple methodology for determination of yttrium as an inert marker in digestibility studies

The need to develop a fast, simple and low cost methodology for the determination of yttrium in fish diets and faeces using a microwave digestion system and atomic absorption spectrometry with flame atomization analysis was the main aim of this study. The final methodology consisted in the digestion of approximately 300 mg of dry fish diet or 100 mg of dry fish faeces in teflon vessels using Parr reactor bombs, at high pressure, in a domestic microwave system with nitric acid solution. After digestion, 330 μl of a 120 mg potassium nitrate/ml solution was added to each solution. Yttrium was determined using a calibration with aqueous standards. Analytical difficulties and problems encountered during the optimizations were overcome and the application of the final methodology to the fish diets and faeces samples was carried out with suitable results.