Hyphenated technique for investigation of nickel complexation by citric acid in xylem sap of cucumber plants

A size-exclusion high performance liquid chromatographic-inductively coupled atomic emission spectrometric (SEHPLC-ICP-AES) method was developed in order to elucidate the role of citric acid in the complexation of nickel in xylem saps of cucumber plants. The complexation of nickel by citric acid was modeled by preparing standard solutions of nickel(II) nitrate or sulfate whose Ni concentration was 2 mug/cm(3) and citric acid whose concentration ranged between 100 and 500 mug/cm(3). By passing these model solutions through the column, the higher the concentration of the citric acid, the greater was the shift of the Ni peak toward the retention time of the citric acid molecules detected with UV spectrometry. This may be evidence for the complexation capability of citric acid. The method was employed for xylem saps originating from nickel-contaminated cucumber plants previously grown in nitrate or urea-containing nutrient solutions. The obtained results for those real and spiked samples with citric acid showed similarity to that of the solutions containing citric acid and nickel. (C) 2002 Elsevier Science B.V. All rights reserved.