Determination of germanium in plant and soil samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR CS GFAAS) with solid sampling

Abstract

Germanium (Ge) is commonly an unreported trace element in environmental samples due to the lack of reliable analytical methods. Besides atomic mass spectrometric methods (ICP-MS) and atomic emission spectroscopy (OES), graphite furnace atomic absorption spectrometry (GFAAS) offers the sensitivity that is needed in biological and environmental analysis. However, until recently AAS-techniques for the quantification of Ge were solely described for liquid samples and require time consuming sample preparation steps involving total dissolution of the sample matrix. In the present study we modified an existing method for the determination of Ge in liquid samples by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR CS GFAAS) towards its applicability to solid samples.Similar to liquid HR CS AAS, the addition of Pd/Mg(NO3)2 as modifier was necessary to avoid analyte losses. To achieve a homogeneous wetting of the solid sample Triton X-100, a non-ionic surfactant, was added together with the modifier. A biomass weight of 0.1–0.2 mg was appropriate for the solid sampling set-up, to which 20 μL of modifier, including 0.1% surfactant, was added. The furnace temperatures were adjusted to 90–140 °C for the drying process, to 1500 °C for pyrolysis and to 2550 °C for the atomisation step. Various calibration options were also considered realising routine analysis. Considering Ge concentrations in various environmental samples we observed no significant differences between results obtained from HR CS AAS and ICP-MS, respectively. The analytical technique demonstrated a detection limit for Ge down to 500 μg kg−1 Ge by a characteristic mass of 50 pg for selected biomass samples. The novel method can be applied in geochemical laboratories equipped with HR CS GFAAS devices to determine Ge in range of 0.7–360 mg kg−1 Ge in solid environmental samples without any sample preparation steps except of grinding.