An accurate and precise ion chromatographic (IC) method for determination of total Cu, Ni, and Zn in soils was developed. The sample preparation method consists of three steps: (i) digestion of the soil sample by using HNO 3 , HClO 4 , and HF; (ii) extraction of the metals of interest by using dithizone in CHCl 3 ; and (iii) destruction of the metal‐dithizonate complex with HNO 3 . The system consisted of a guard (HPIC‐CG5) column and a separator (HPIC‐CS5) column followed by postcolumn reaction with 4‐(2‐pyridylazo) resorcinol ( par ), to form colored metal complexes. The absorbance of the metal‐ par complexes was measured by an ultraviolet‐visible light ( uv‐vis ) detector at 520 nm. Two different eluents were required for separation of these and other metals. Simultaneous determination of Cd, Cu, Mn, and Zn was achieved by using an eluent containing 4 m M 2,6‐pyridinedicarboxylic acid ( pdca ) and 50 m M HOAc‐NaOAc buffer (pH 4.8). Simultaneous determination of Cu, Ni, Pb, and Zn was accomplished by using an eluent containing 40 m M oxalic acid and 50 m M HOAc‐LiOAc buffer (pH 4.8). Results by the IC method for determination of total Cu, Ni, and Zn in 14 soils were in good agreement with those obtained by atomic absorption spectrophotometry, but results also showed that the proposed IC method is inadequate for determination of total Cd, Mn, and Pb in soils.
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Basta et al. (1990) studied this question.