Absorption spectra of the 4f electron transitions of the praseodymium complex with 1-cyclopropyl-6-fluoro-1,4-dihydro-7-(4-ethyl-1-piperazinyl)-4-oxo-3-quinoline carboxylic acid hydrochloride and its analytical application

The absorption spectra of the praseodymium complex with 1-cyclopropyl-6-flu oro-1,4-dihydro-7-(4-ethyl-1-piperazinyl)-4-oxo-3-quinoline carboxylic acid hydrochloride (NNFX) has been studied by normal and derivative spectrophot ometry. The complex showed maximum absorption at 350 nm at pH 6.0. The stoi chiometry of the Pr-NNFX complex was calculated by the molar ratio and cont inuous variation methods. The ratio of Pr to NNFX was 1:3. The absorption b ands of the 4f electron transitions of the praseodymium complex with NNFX a re enhanced markedly, especially the wavelength at 481 nm. Using the third- derivative spectrum, the calibration graph is linear over the range 2.5 x 1 0(-5) - 3.5 x 10(-4) mol dm(-3) for praseodymium. The detection limits (sig nal-to-noise ratio of 2) is 1.4 x 10(-6) mol dm(-3). The relative standard deviation is 1.2% for 7.0 x 10(-5) mot dm(-3) of praseodymium. A method for the direct determination of praseodymium in rare earth mixtures with good accuracy and selectivity is described.