220-224 LCE Apr05qk

Introduction The identification and quantification of hexavalent chromium in solid samples is an important factor in characterization studies. The speciation of elements is a developing feature of analytical methods; the evaluation of the environmental and biological impact of the Cr (VI) compounds on environmental matrices is fundamental because of their demonstrated toxicity and potential carcinogenicity on humans.1,2 The regulatory agencies in Italy have established restrictive limits of concentration on soil samples from reclamation areas.3 The concentration limit depends on the final destination (use) of the reclaimed soil, a maximum of 2 mg/Kg (dry matter) for residential areas and a maximum of 15 mg/Kg (dry matter) for industrial areas. The hexavalent chromium extraction and analysis are reported in several official methods using different analytical techniques; based on spectrophotometric electrochemical methods, determination or based on atomic absorption spectrophotometry and plasma mass spectrometry.4,5,6 Among the valence specific direct measurements, we investigated the ion chromatography analysis coupled with spectrophotometric detection7,8,9,10 as described in EPA method 719911 and modified12 in order to reach lower detection limits. (The proposed method allows a detection limit of 0.01 μg/L of hexavalent chromium and 0.1 μg/L of quantification limit as can be seen from Figure 1).13 Chromatographic and detection conditions are given in Table 1. In the set up of the proposed protocol, we focused our efforts on the extraction procedure of hexavalent chromium from solid samples; well aware that the accuracy of the methods on chromium speciation in these kind of matrices needs various improvements, as is shown in a review by Marques et al.14 The lack of reported recovery by most authors emphasizes this fact. As reported in several methods, in order to quantify Cr (VI) in solid samples, three criteria have to be satisfied: the extraction solution must dissolve all forms of Accelerated and Automated Extraction of Hexavalent Chromium from Solid Waste Materials Coupled with Ion Chromatography Determination