Spectrophotometric, potentiometric, and gravimetric determination of lanthanides with peri-dihydroxynaphthindenone

Abstract

Sensltlve and reasonably selectlve methods are descrlbed for the spectrophotometrlc, potentlometrlc, and gravlmetrlc determfnatlon of lanthanldes using perl-dlhydroxynaphthlndenone as a novel chromogenlc and preclpltatlng reagent. The reagent forms a stable 1:2 (metakreagent) type of complex wlth light lanthanides at pH 2-7 In 1:l ethanol-water mlxture. Low metal concentratlons ( < I O pg/mL) develop colored specles ( A, 580-590 nm, emax (4-6) X lo4 L mol-' cm-') whlch obey Beer's law. Quantltatlve preclpltatlon of the complexes from metal solutlons of concentratlons > 100 pg/mL permlts both gravlmetrlc quantltatlon by lgnltlng the preclpltates to the metal oxides and potentlometrlc tltratlon of the excess reagent. Results wlth an average recovery of 98% (standard devlatlon 0.7%) are obtainable for 0.1 kg to 200 mg of all light lanthanldes. Many forelgn Ions naturally occurrlng or frequently assoclated wlth lanthanldes do not Interfere or can be tolerated.