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Synthesis and use of 3-hydroxy-2-[1'-phenyl-3'-(p-methylphenyl)-4'-pyrazolyl]-4-oxo-4H-1-benzopyran (HPMPB): A novel analytical reagent for trace determination of vanadium (V) in various samples

Raj Kamal, Agnihotri Nivedita, Agnihotri Rajesh, Prakash Om, J.R.Mehta

Vanadium (V) in trace amounts forms an intense green 1:3 (M:L) complex with 3-hydroxy-2-[1'-phenyl-3'-(p-methylphenyl)-4'-pyrazolyl]-4-oxo-4H-1- benzopyran (HPMPB) in acetic acid medium(0.2 mol L-1) which is extractable into toluene and is stable for more than 10 h. BeerÂ’s law is obeyed in the vanadium concentration range of 0-1.2 ìg mL-1. Molar absorptivity, detection limit and SandellÂ’s sensitivity when applying spectrophotometric determination at the wavelength of 415 nm, are 2.496ï‚´104L mol-1 cm-1, 7.628ï‚´10-5gmL-1 and 0.0020 ìg VV cm-2, respectively. The correlation coefficient being r = 0.9967.Ascorbic acid, oxalate and hydrogen peroxide interfere in the determination. The method handles has been satisfactorily applied to the analysis of vanadium in various synthetic, technical and natural samples, including reverberatory flue dust and high speed steel with super rapid extra 500.