Spectrophotometric and fluorometric determination of traces of molybdenum in soils and plants

The reaction of the molybdenum oxypentathiocyanate ion with the dyestuff Rhodamine B (RhB) produces the ternary complex. MoO(SCN)(5)(RhB)(2) The formation of this complex is accompanied by a colour change and by extinction of the fluorescence of RhB. A spectrophotometric and fluorometric method for the determination of Mo has been developed from these observations. The method is free from interferences and has detection limits of 0.1 mug and 0.05 mug of Mo for absorption and fluorescence measurements, respectively. The spectrophotometric method is applicable to the determination of Mo in soils and the fluorometric method is suited to the determination of Mo in plants.