On-line removal of interferences via anion-exchange column separation for the determination of germanium, arsenic and selenium in biological samples by inductively coupled plasma mass spectrometry

Abstract

A method was developed for the determination by inductively coupled plasma mass spectrometry of germanium, arsenic and selenium in urine and blood after microwave acid digestion and on-line anion-exchange separation. After acid digestion, the analytes exist mainly as H₂GeO₃, H₃AsO₃, H₃AsO₄, H₂SeO₃ and H₂SeO₄ in the resulting sample solution. Separation of the analytes is achieved by adsorption of the analytes as anionic species on the column in relatively alkaline media with subsequent desorption of the analytes from the column as undissociated neutral species in acidic media. By loading the digested sample, adjusted to about pH 11.5, onto the column of the on-line separation system, the analytes as well as CI and S, which may cause spectral interference in the inductively coupled plasma mass spectrometric determination, are retained on the column. In the subsequent elution step with eluent of about pH 1.6, the analytes are desorbed from the column while Cl and S are still retained. With this on-line analytical system, the determination of ⁷²Ge and ⁷⁵As could be completely free from the interference caused by ³⁵Cl³⁷Cl and ⁴⁰Ar³⁵Cl, respectively. By following the established microwave digestion and on-line separation process, the detection limits obtained for Ge, As and Se were as low as 0.07, 0.13 and 0.3 ng ml^–1, respectively. The analytical reliability of the proposed method was evaluated by analysing commercially available urine and whole blood standards, and the results obtained were found to be in reasonably good agreement with the literature values.