Two solid sorbents based on the introduction of the reagent beta-nitroso-alpha-naphthol in a polymeric matrix were employed as packing material in a flow injection preconcentration system for the determination of copper in food samples. The sorbents were prepared by two different means: functionalization of Amberlite XAD-4 by coupling beta-nitroso-alpha-naphthol to a methylene spacer or impregnation of the copolymer with a solution containing the reagent. Both resins allowed copper preconcentration with very good analytical features. The enrichment factor obtained was 29 (both sorbents) for 60 s preconcentration time. For 180 s preconcentration time, enrichment factors of 58 (functionalized resin) and 61 (loaded resin) were obtained. Detection limits were 0.7 and 0.4 mu g L-1 for functionalized and loaded resin, respectively. The procedure was applied to the analysis of bean, peanut and soybean samples. Studies performed in this work demonstrate that both functionalized and loaded NN-XAD have similar analytical characteristics and they are appropriate for employment in the on-line system. (c) 2007 Elsevier B.V. All rights reserved.