The determination of germanium by hydride generation-atmospheric pressure glow discharge optical emission spectrometry (HG-APGD OES)

Abstract

Hydride generation (HG) was combined with an atmospheric pressure glow discharge (APGD) to determine Ge by optical emission spectrometry (OES) employing the Ge I 265.1 nm emission line. It was revealed that efficient atomization of GeH₄ and excitation of Ge atoms require a microplasma with a higher energy density than other hydride-forming elements such as As, Sb, and Se. The operating conditions were optimized: discharge gap = 0.5 mm, cathode nozzle diameter = 0.7 mm, current = 45 mA, and carrier/discharge gas flow rate of 400 mL min⁻¹ He. The measurement repeatability (n = 10) was within the range of 3.3–4.8 %, demonstrating the high stability of the novel HG-APGD system. The upper limit of linearity was 1000 μg L⁻¹ Ge, and the method was resistant to interferences from easily ionized elements (Ca, K, Mg) at concentrations up to at least 100 mg L⁻¹. The detection limit (DL) of Ge (0.4 μg L⁻¹) was comparable to the values achieved using more expensive and sophisticated analytical instrumentation based on inductively coupled plasma (ICP) or microwave induced plasma (MIP) combined with OES. The trueness of HG-APGD OES was confirmed through a recovery test, which showed a high agreement between spiked and measured concentrations of Ge in the matrix of bottled, mineral-rich, river, and tap water samples. The Ge recoveries ranged from 99 % to 114 % at the spiking concentration of 10–20 μg L⁻¹.