Spectrophotometric determination of rhenium(IV) with thiocyanate, TX-100 and N,N′-diphenylbenzamidine

A spectrophotometric method to determine rhenium(IV) at trace level is based on the extraction of Re(IV)-SCN- complex in sulphuric acid media wit:h N,N'-diphenylbenzamidine(DPBA) in presence of a non-ionic surfactant triton X-100 (TX-100) in chloroform. The complex shows maximum absorbance at 435 nm with a molar absorptivity value of' 4.24 x 10(4) L mol(-1) cm(-1) at an acidity range 3.5-6.5 M H2SO4. The method followed Beer's Law for the system Re(IV)-SCN--('TX-100)-DPBA upto 4.0 mu g Re(IV) mL(-1). The detection limit of the method is 5 ppb. None of the tested foreign ions, except molybdenum(VI), interfere with the determination of rhenium. The interference due to molybdenum could effectively be removed by prior precipitation with oxine. The effect of various analytical parameters on the extraction of the metal are discussed.