Selective Determination of Trace Level Chromium(III) by Ion-Pair Reversed-Phase High-Performance Liquid Chromatography Based on Color Formation with 4-(2-Pyridylazo)resorcinol in the Presence of Triethanolamine

The color reaction of chromium(II) ion with 4-(2-pyridylazo)resorcinol is quantitatively accomplished within 30 min in boiling triethanolamine buffer solution at pH 8.5–8.9 to produce the red chelate having the molar absorption coefficient of 6.21 × 10⁴ dm³ mol⁻¹ cm⁻¹ at 525 nm. On the basis of this finding, a rapid and highly selective ion-pair reversed-phase partition liquid chromatography/photometric detection system has been developed for the determination of trace chromium at the ng cm⁻³ level. A detection limit of chromium is down to 0.5 ng cm⁻³ at 0.005 absorbance unit full-scale range (525 nm), being free from the Interferences by 100–200 ng cm⁻³ each of common cations such as AI(III), V(V), Mn(II), Fe(III), Co(II), NI(II), Cu(II), Zn(II), and Cd(II) ions.