Continuous tandem on-line separation inductively coupled plasma optical emission spectrometry selective determination of germanium in zinc electrolytic solutions Original Research Article

Germanium is usually present at low levels in zinc ores. Due to its harmful effects on the process of the electrodeposition of zinc, it is important to control its concentration in zinc electrolytic baths. A sensitive, precise, selective and automated method based on a continuous tandem on-line separation device in connection with a inductively coupled plasma optical emission spectrometry (ICP-OES) for the determination of germanium in such samples is proposed. Germanium is continuously complexed by HCl 8.5 M and then extracted in a continuous mode as GeCl4 into xylene. That xylene phase is continuously separated from the aqueous phase by a liquid–liquid separator (two separators have been tested: a membrane separator and a gravitational separator), and then mixed on-line with NaBH4 in dimethylformamide and glacial acetic acid solutions. So, GeH4 is thus continuously generated directly from the organic phase, separated by means of a stream of argon in a gas–liquid separator, and introduced in the ICP torch. Optimisation of experimental conditions for the tandem separation and ICP-OES detection are investigated. The detection limit attained is 1 ng ml−1 with the membrane separator and 3 ng ml−1 with the gravitational separator, and the precision is 3 and 5%, respectively. Finally, the proposed methodology has been applied to the determination of germanium in three real zinc electrolytic bath samples and compared with a routine method. Good agreement has been found.