Eluent composition effect on ion chromatographic determination of oxyanions in solutions equilibrated with soils

Summary

Methods based on simultaneous determination of oxy-anions in soil extracts are needed for studies of competitive adsorption of oxyanions by soils. We studied the effect of NaHCO₃/Na₂CO₃ and NaOH/Na₂CO₃ concentrations on ion chromatographic (IC) determination of PO ³⁻₄ , AsO ³⁻₄ , SeO ²⁻₄ , SeO ²⁻₃ , WO ²⁻₄ , and MoO ²⁻₄ in a 10-mM NaCl matrix equilibrated with soils by using a Dionex 2002i IC unit. The eluent, 6.0 mM NaOH+4.5 mM Na₂CO₃, resolved the 10 mM Cl⁻ from the six oxyanions. Elution times for Cl⁻, SeO ²⁻₃ , SO ²⁻₄ , NO ⁻₃ , SeO ²⁻₄ , PO ³⁻₄ , WO ²⁻₄ , MoO ²⁻₄ , and AsO ³⁻₄ were 1.7, 2.7, 5.2, 6.1, 7.8, 10.5, 14.3, 17.7, and 21.2, respectively. The recovery of 0.2-mM oxyanion standards added to the soil solutions ranged from 93.0 to 106.8%, with coefficients of variation ranging from 0 to 14.3%. The detection limits of the oxyanions studied ranged from 0.3 μM for SeO ²⁻₃ to 9.0 μM for AsO ³⁻₄ .