DETERMINATION OF TRACE AMOUNTS OF MOLYBDENUM IN WATERS WITH CARMINIC ACID BY ION-EXCHANGE SPECTROFLUOROMETRY

A spectrofluorimetric method for the determination of trace amounts of molybdenum was developed, based on ion-exchange spectrofluorimetry (IEF). Molybdenum reacts with carminic acid to give a red fluorescent complex, which was fixed on a dextran-type anion-exchange gel. The fluorescence of the gel, packed on a 1-mm quartz cell, was measured directly using a solid-surface attachment. The applicable concentration range was from 1.0 to 15.0 mu g.l(-1), with a relative standard deviation of 1.4 % and a detection limit of 0.3 mu g.l(-1). The method was applied to the determination of molybdenum in natural waters. This method is more sensitive and selective than that using carminic acid alone.