An indirect method for the spectrofluorimetric determination of trace amounts of germanium after extraction as an ion association complex with rhodamine B in the presence of chromotropic acid

A highly sensitive and selective spectrofluorimetric method for the determination of 0.05-2.00 μg germanium is described. Germanium is treated with chromotropic acid at pH 2.5 and the resultant anionic complex is extracted as an ion pair with rhodamine B into toluene. Addition of butanol to the organic extract releases the fluorescent dye and facilitates its measurement at 570 nm after exciting at 540 nm. The method provides a detection limit of 0.003 μg ml-1 and is virtually free from interference from extraneous ions. The relative standard deviation is 2.9% for ten determinations of 1.0 μg germanium. The method has been applied to the determination of germanium in various ores, minerals and rock samples.