ION CHROMATOGRAPHIC DETERMINATION OF SCN- IN SOILS

An ion chromatographic (IC) procedure designed to avoid interferences from both plant tissues and soluble soil organic materials was developed to measure SCN- in soil extracts. Ionic thiocyanate (SCN-) was extracted from 4 g of soil with 10 mL of 0.01 M CaCl2 and the concentration determined with suppressed IC in combination with conductivity detection. Extraction efficiency from six SCN--amended soils averaged 94% for SCN- concentrations of 1.25-12.5-mu-g of SCN-/g of soil. Colorimetric determination of SCN- in soil extracts was comparable to IC at higher amendment rates but averaged only 67% of the amount added with spikes of 1.25-mu-g of SCN-/g of soil. The IC method is compatible with infrared analysis of isothiocyanates when soil is extracted simultaneously with CaCl2 and CCl4. Various anions including S2-, S2O4(2-), SO3(2-), SO4(2-), S2O3(2-), and S4O6(2-) do not interfere with SCN-quantification.