Extractive spectrophotometric determination of chromium(III) in steels using 4-(2-pyridylazo)resorcinol and xylometazoline hydrochloride

ANALYSTANALYST Pub Date: DOI: 10.1039/AN9861101167

Abstract

Chromium(III) forms a 1 : 3 orange-red anionic complex with 4-(2-pyridylazo)resorcinol (PAR) when heated in an acetate buffer medium (pH 4.0–5.5) on a water-bath, and this complex can be extracted quantitatively with the xylometazolonium (XMH) cation into chloroform. This ion association system exhibits a maximum absorbance at 530 nm, with a molar absorptivity of 4.8 × 104 l mol–1 cm–1 and obeys Beer's law in the range 0–1.0 μg ml–1 of chromium(III). Job's method of continuous variations revealed that the composition of the extracting species is 1 : 3 : 1 for Cr(III)-PAR-XMH. EDTA, when added after the formation of the complex between Cr(III) and PAR, can effectively mask the interference from Ca(II)(1000 μg), Ba(II)(1000 μg), Sr(II)(1000 μg), Tl(II)(1000 μg), Cd(II)(1000 μg), Mg(II)(500 μg), Hg(II)(500 μg), Al(III)(500 μg), Bi(III)(400 μg), V(V)(200 μg), Mn(II)(200 μg), Mo(VI)(200 μg), Cu(II)(150 μg) and W(VI)(150 μg) without any interference in the determination of chromium. This makes the method highly selective.

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