FLOW-INJECTION DETERMINATION OF VARIOUS COUMARINS IN A MIXTURE BY MEANS OF DIFFERENTIAL FLUOROMETRY

A differential-fluorimetric flow-injection determination of scopoletin e or umbelliferone in binary mixtures with herniarine based on the pH- dependence of the fluorescence spectra of the analytes is described. A simple flow system involving a double-injection valve for the simulta neous introduction of a buffer and a sample plug into a carrier, and a flow-through fluorimetric detector is used. Two variants of the metho d enable the determination of greater than or equal to 1 mu mol . l(-1 ) of scopoletione or umbelliferone in the presence of less than or equ al to 100-fold molar excess of herniarine. The procedure was applied t o the determination of umbelliferone and herniarine in a commercial ph armaceutical preparation.