An automatic procedure for determination of available iron in Indian soils

Abstract

An on‐line automatic procedure for the flow injection analysis (FIA) determination of iron (Fe) in a variety of soil extracts with common laboratory reagents, i.e., thiocyanate, thiocyanate +1,10‐phenanthroline/bipyridine has been tested. The apparent molar absorptivity of the complexes lies in the range of (5.5–7.0)x10³ L mole^‐1 cm^‐1 at an absorption maximum between 470–495 nm. The detection limit of the method is 15 ppb Fe. The sample output is 100 samples/hr. Almost all ions associated with Fe in the soil extract do not interfere in this method. Optimization of FIA variables, composition of the complex, and effect of other ions on the determination of Fe are discussed. The method has been used for determination of Fe status in a variety of agricultural soils in east Madhya Pradesh, India.