Preparation of 15N-labeled Potassium Ferrocyanide for Tracer Studies

Isotopic labels are widely used to trace the fate and cycling of common environmental contaminants. Many of the labeled materials are not available commercially and, depending on the complexity of the substance, the label and the enrichment level, custom syntheses are costly. A simple, straightforward, and cost effective method for the preparation of a highly enriched, 15N-labeled potassium ferrocyanide (K4[Fe(C15N)6]*3H2O) has been developed to meet the requirements of related tracer experiments and minimize their costs. In this case, the 15N label was used to quantify iron cyanide detoxification (biodegradation and/or transformation) within soil-plant-systems. 15N-labeled potassium cyanide (KC15N) and a ferrous iron salt have been used for the synthesis. Extensive qualitative and quantitative analyses showed a product, entirely identical in its functional and elemental components to commercial non-labeled K4[Fe(CN)6]*3H2O and in its 15N enrichment to the KC15N used for its synthesis. To investigate their behavior and fate in various environmental compartments, other labeled iron or metal cyanide complexes might be synthesized in analogous manner.