AN EXTRACTIVE SPECTROPHOTOMETRIC METHOD OF DETERMINATION OF MOLYBDENUM(VI) USING 3-HYDROXY-2-(4-METHOXYPHENYL)-6-METHYL-4H-CHROMEN-4-ONE

3-Hydroxy-2-(4-methoxyphenyl)-6-methyl-4H-chromen-4-one (HL) behaved as a sensitive spectrophotometric reagent for molybdenum(VI). The metal ion formed a yellow complex with the reagent in acetic acid medium. The complex was extractable into 1,2-dichloroethane and the absorbance values remained unchanged for more than one week. Spectral data showed the formation of 1:2 species with lambda(max) value at 411 nm. Beer's law was obeyed over the concentration range of 0-2.3 ppm. The molar absorptivity and Sandell's sensitivity were calculated to be 5.61 x 10(4) dm3 mol-1 cm-1 and 0.0017 mug Mo cm-2 respectively, at 411 nm. The effect of as many as 41 cations and 28 anions and complexing agents was studied. Out of these only Sn(II), Ce(IV), citrate, oxalate, disodium dihydrogen ethylenediaminetetraacetate, and hydrogen peroxide interfered seriously. For ten replicate determinations of 1 mug Mo cm-3 the standard deviation was 0.008 with a relative mean error of +/-0.09%. The method is simple, selective, precise and rapid. It has been applied satisfactorily to the determination of molybdenum in steels, waters and flue dust samples.