Use of a new 3-hydroxy-2-[1'-phenyl-3'-(p-chlorophenyl)-4'-pyrazolyl]-4-oxo-4H-1-benzopyran (HPCPB) as an analytical reagent for trace determination of vanadium(V)

Vanadium(v) in trace amounts forms an intense green 1 : 3 (M : L) complex with 3-hydroxy-2-[1'-phenyl-3'-(p-chlorophenyl)-4'-pyrazolyl]-4-oxo-4H-1-benzopyran (HPCPB) in acetic acid medium (0.1 M) which is extractable into carbon tetrachloride and is stable for more than 3 h. Beer's law is obeyed in the vanadium concentration range of 0-1.4 mg mL(-1). Molar absorptivity, detection limit and Sandell's sensitivity when applying spectrophotometric determination at the wavelength of 410 run, are 2.2 x 10(4) L mol(-1) cm(-1), 5.48 x 10(-5) g L-1 and 0.0023 mg V cm(-2), respectively. The correlation coefficient being r = 1.0001. Ascorbic acid, dithionite, oxalate, EDTA and hydrogen peroxide interfere seriously in the determination. The method handles satisfactorily the analysis of various samples of varying complexity.