An automated preconcentration system for the determination of manganese in food samples

In this work, an on-line automated system for the preconcentration and evaluation of manganese in food samples is proposed. The preconcentration of manganese ions is carried out using two mini-columns packed with 4-(5′-bromo-2′-thiazolylazo)orcinol (Br-TAO) loaded polyurethane foam. After a preconcentration step, a stream of hydrochloric acid is passed through the mini-column in order to transport the manganese directly to the flame atomic absorption spectrometer. The sample frequency was 60 h⁻¹ for a 60 s preconcentration time. The limit of detection and enrichment factor were 0.70 μg L⁻¹ and 17, respectively. The accuracy of the procedure was evaluated by analysis of biological reference materials (spinach leaves, tomato leaves and pine needles). The procedure was successfully applied for the evaluation of manganese in several food samples, such as corn, rice and cassava flour.