Abstract
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.