Derivative spectrophotometric determination of Nd, Ho and Er in rare earthmixtures with 1-ethyl-6,8-difluoro-7-(3-methyl-1-piperazinyl)-4-oxo-1,4-dihydro-3-quinoline carboxylic acid

The second derivative spectrophotometric method has been developed as a pro cedure for the determination of neodymium, holmium and erbium in mixed rare earths. It was found that the 1-ethyl-6, 8-difluoro-7-(3-methyl-1-piperazi nyl)-4-oxo-1,4-dihydro-3-quinoline carboxylic acid forms stable complexes w ith neodymium, holmium and erbium ions in the pH 9.2-10.5 range. In the sec ond derivative spectra the optimum analytical signals for neodymium, holmiu m and erbium are at 576.2 (+) -574.5 (-)nm, 444.2 (+) -447.8 (-)nm and 516. 0 (+) -517.2 (-)nm. respectively. Beer's law is obeyed from 5.0 x 10(-5) M to 2.5 x 10(-4) M of neodymium, holmium and erbium, The quantification limi ts (10 Sb) were 1.2 x 10(-5) M for Nd, 9.7 x 10(-5) M for Ho and 3.0 x 10(- 6) M for Er,