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Spectrophotometric Determination of Vanadium(V) by means of 1-Phenyl-2-methyl-3-hydroxy-4-pyridone

The application of 1-phenyl-2-methyl-3-hydroxy-4-pyridone (HX) for the spectrophotometric determination of V(V) by extraction in chloroform was investigated. It was found that depending on the extraction conditions three types of complexes are formed. At pH 1.0-2.2 an orange complex of the composition VO2X(HX) and maximal absorption at 497 nm is formed. However, at 0.75-1.25 M hydrogen ion concentration and in the presence of an excess of chloride ions a blue complex VO2Cl(HX)2 with maximal absorption at 625 nm was found. In the presence of an excess of perchlorate ions at 0.3-0.4 M hydrogen ion concentration a blue complex VO2ClO4(HX)3 with maximal absorption at 605 nm was established. Procedure for the determination at 497 and 625 nm are very fast and simple. The molar absorptivity at 497 nm is 4100 l mol(-1) cm(-1) and at 625 nm 5600 l mol(-1) cm(-1). The photometric sensitivity of the method, as defined by Sandell, is 0.0124 micro g V cm(-2) at 497 nm and 0.0091 micro g V cm(-2) at 625 nm. The reproducibility of the measurements expressed as standard deviation, is 0.3-2%, depending on the vanadium concentration. Beer-s law is obeyed.

vanadium ; spectrophotometric determination ; 4-pyridone

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