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The chromogenic reagent 4,4′-dichloro(3-mercapto-1,5-diphenylformazan), Cl 2 H 2 D Z , forms a yellow–red-coloured complex with selenium(IV). The produced complex species was extracted quantitatively into n -hexane, and its absorbance was measured at 416  nm. The chemical composition of the extracted selenium(IV)-Cl 2 H 2 D Z chelate and the molar absorptivity at 416  nm were found to be [SeO (Cl 2 HD Z ) 2 ] and 9  ×  10 4   L  mol -1   cm -1 , respectively. The values of the extraction constants ( K D , K ex , β ) enable a convenient application of the proposed system for the liquid–liquid extraction procedure and sequential spectrophotometric determination of traces of inorganic selenium(IV) and/or selenium(VI) after reduction of the later to selenium(IV) with HCl (6  M). Beer's law and Ringbom's plots were obeyed in the concentration range 0.01–20 and 0.5–19  µg  mL -1 of selenium(IV), respectively, with a relative standard deviation of 2.2%. The proposed method has been successfully applied to the determination of selenium(IV) or (VI) and total inorganic selenium(IV) and (VI) in tap and freshwater samples. [ABSTRACT FROM AUTHOR]