Copper fractionation in plasma, muscle and liver of Nile tilapia was performed after protein separation by 2D-PAGE. SR XRF analysis indicated the presence of copper in three protein spots of plasma, and in two protein spots of muscle and liver, respectively. Copper ions were found to be distributed mostly in proteins that had a molar mass of less than 54 kDa and greater than 13 kDa and a pI in the 5.3-9.3 range. The copper concentration bound to these proteins was determined by GFAAS which showed concentrations in the 1.20-4.82 mg g-1 range.

The aim of the present work was to develop and optimize a method for determination of bioavailable phosphorus in samples of feces and fish feed using ultrasound extraction and subsequent quantification by visible spectrophotometry. Using as extractor solution HNO3 0.50 mol L-1, the great conditions of extraction established were: sample mass - 100 mg, samples granulometry - < 60 µm, sonification time - five cycles of 40 s and ultrasound potency - 136 W. The proposed method was applied in studies of digestibility of this nutrient in different feeds used in diets of juvenile of Nile tilapia.

Neste trabalho, um método simples, rápido e sensível, é proposto para determinação de manganês em amostras de fezes e rações de peixes por espectrometria de absorção atômica em forno de grafite (GFAAS) utilizando-se a introdução direta de suspensões das amostras no tubo de grafite. Os limites de detecção (LOD) e de quantificação (LOQ) calculados em relação a 20 leituras do branco das suspensões (0,50 % m/v de fezes ou ração isentas de manganês) foram de 28 e 92 µg kg¹ para as suspensões padrão de fezes e de 34 e 110 µg kg¹ para as suspensões padrão de ração. O método proposto foi aplicado em estudos de biodisponibilidade de manganês em diferentes amostras de rações de peixes e os resultados mostraram-se de acordo com os resultados obtidos utilizando-se amostras previamente mineralizadas por digestões ácidas em forno de microondas.

This paper presents a simple, fast and sensitive method to determine manganese in samples of feces and fish feed by graphite furnace atomic absorption spectrometry (GFAAS) by the direct introduction of slurries into the graphite tube. The limits of detection (LOD) and quantification (LOQ) calculated for 20 readings of the blank of the standard slurries (0.50 % m/v of feces or feed devoid of manganese) were 28 and 92 µg kg-1 for the standard feces slurries and 34 and 110 µg kg-1 for the standard feed slurries. The proposed method was applied in bioavailability studies of manganese in different fish feeds and their results proved compatible with those obtained for samples mineralized by acid digestion using microwave oven.