Determination of molybdenum and cobalt in plants, soils and forages with flameless atomic absorption-spectrometry

A method is described for the direct determination of molybdenum and cobalt in acid digestions of plants, forages and soils, and in soil saturation extracts by the techniques of flameless atomic absorption spectrometry in the graphite furnace. The accuracy of the method was tested by comparison with a combined solvent extraction-flame AAS-technique for Mo, and with neutron activation analysis for Co. A very good agreement was found between these different methods and the flameless AAS. Contents of plants from different locations were found between 0.19 and 3.34 ppm Mo and between 0.06 and 4.64 ppm Co. Plants grown on serpentine soils showed relatively high levels of Co, but low levels of Mo. Total amounts in different soils were found between 0.58 and 5.73 ppm Mo and between 6.97 and 14.20 ppm Co. The concentrations in soil saturation extracts were evaluated in a range between 0.4 and 125 ppb Mo, and between 0.6 and 43 ppb Co. The solubility of Mo and Co in soils is influenced by the soil pH. (author)