ZnO nanoparticles as an adsorbent in ultrasound-assisted dispersive micro solid-phase extraction combined with high-resolution continuum source electrothermal atomic absorption spectrometry for determination of trace germanium in food samples

An ultrasound-assisted dispersive micro solid-phase extraction (USA DMSPE) is presented for the separation and preconcentration of trace levels of germanium with the use of zinc oxide nanoparticles (nano-ZnO) as an adsorbent prior to high-resolution continuum source electrothermal atomic absorption spectrometry (HR-CS ET AAS). The experimental parameters (amount of ZnO, pH of sample solution, ultrasonication and centrifugation time, ZnO slurry preparation) were studied. Effective preconcentration of trace germanium with 20 mg of ZnO was achieved at pH 9. After extraction, adsorbent with analyte was mixed with 200 μL of H2O to prepare slurry. The concentration limit of detection was 0.003 ng mL− 1 for total Ge. The achieved preconcentration factor was 15. The relative standard deviations (RSDs, %) for determination of the analyte in real samples were 4-23%. The accuracy of this method was evaluated by the extraction and determination of total Ge after spiking of certified reference materials: INCT-TL-1 (Tea Leaves) and INCT-MPH-2 (Mixed Polish Herbs). The measured germanium contents were in satisfactory agreement with the added amounts (according to the t-test for a 95% confidence level). The presented method has been successfully applied for the determination of the analyte in real food samples (tea, goji berries, ginger products and aloe vera juice).