9-(2,4-dihydroxyphenyl)-2,3,7-trihydroxyl-6-fluorone as analytical reagent for spectrophotometric determination of molybdenum in plant tissues

A highly sensitive and selective spectrophotometric method is proposed for direct determination of trace molybdenum in plant tissues. The method is based on the reaction of molybdenum (VI) with a new analytical reagent 9-(2,4-dihydroxyphenyl)-2,3,7-trihydroxyl-6-fluorone (DHPTHF). Under optimum reaction conditions, DHPTHF reacts with molybdenum (VI) and forms a red complex with the maximum absorption peak at 523 nm. The color reaction is rapidly completed and the absorbance remains stable for at least a week at room temperature. The apparent molar absorption coefficient, the limit of quantification and the limit of detection were 1.4×105 L mol−1 cm−1, 6.6 ng mL−1 and 2.0 ng mL−1, respectively. A linear absorbance was obtained for 0-6 μg of molybdenum (VI) in 10 mL solution. The effect of various substances on the determination of molybdenum was also investigated in detail. Results indicated that most of the studied co-existing substances can be tolerated in considerable amounts, e.g. 150 mg of Ca (II), 100 mg of Mg (II), 5.0 mg of Fe (III) and 50 mg of Zn (II), and do not interfere with the determination of molybdenum. The proposed method offered the advantages of sensitivity, rapidity, selectivity and simplicity without any prior separation or extraction. Moreover, the synthesis and physical and chemical properties of the reagents were also studied.