Pure plus

Serum selenium, iron, zinc, and copper levels were quantified by inductively coupled mass spectroscopy (ICP-MS NexION 350D, PerkinElmer) using methane to reduce polyatomic interferences, following Lubinski et al. [20 (link), 21 (link)]. Calibration standards were prepared by diluting 10 mg/L Multi-Element Calibration Standard 3 (PerkinElmer Pure Plus, PerkinElmer Life and Analytical Sciences, USA) with a blank reagent consisting of a 0.65% solution of nitric acid (Merck, Germany) and 0.002% Tryton X-100 (PerkinElmer, USA). Calibration curves were created using four different concentrations: 0.1 μg/L, 0.5 μg/L, 1 μg/L, and 2 μg/L. Germanium (PerkinElmer Pure, PerkinElmer Life and Analytical Sciences, USA) was used as an internal standard, and ClinChek Plasma Control Level I (Recipe, Germany) was used as a reference material, measured after each of the six samples: where the difference of the reference material measurements exceeded 5%, the entire series was repeated. Each sample was measured in duplicates in different analytical runs. Prior to analysis, all samples were centrifuged (6000 rpm, 15 min) and the supernatant was diluted 100 times with the reagent blank. Technical details, plasma operating settings, and mass spectrometer acquisition parameters are available on request.

Serum selenium levels were quantified by inductively coupled mass spectroscopy (ICP-MS NexION 350D, Perkin Elmer) using methane for reduction of polyatomic interferences. Calibration standards were prepared by dilution of 10 mg/l Multi-Element Calibration Standard 3 (PerkinElmer Pure Plus, PerkinElmer Life and Analytical Sciences, USA) with reagent blank consisting of 0.65% solution of nitric acid (Merck, Germany) and 0.002% Tryton X-100 (PerkinElmer, USA). Calibration curves were created using four different concentrations: 0.1 μg/l, 0.5 μg/l, 1 μg/l, 2 μg/l. Germanium (PerkinElmer Pure, PerkinElmer Life and Analytical Sciences, USA) was used as an internal standard and ClinChek^® Plasma Control Level I (Recipe, Germany) was used as a reference material. Reference material was measured after each of the six samples. If the difference of the reference material measurements was greater than 5%, the entire series was repeated. Each sample was measured in duplicates in different analytical runs. Prior to analysis, all samples were centrifuged (6000 rpm, 15 min) and the supernatant was diluted 100 times with the reagent blank. Technical details, plasma operating settings and mass-spectrometer acquisition parameters are available on request.

Serum selenium levels were measured by inductively coupled mass spectroscopy (ICP-MS ELAN DRC-e, Perkin Elmer) using methane for reduction of polyatomic interferences. Calibration standards were prepared by dilution of 10 mg/l Multi-Element Calibration Standard 3 (PerkinElmer Pure Plus, PerkinElmer Life and Analytical Sciences, USA) with 1% Suprapur® HNO₃ (Merck, Germany). Calibration curves were created using five different concentrations: 1 μg/l, 10 μg/l, 20 μg/l, 50 μg/l and 100 μg/l. Germanium (PerkinElmer Pure, PerkinElmer Life and Analytical Sciences, USA) was used as an internal standard and ClinChek® Plasma Control Level I (Recipe, Germany) was used as a reference material. Before analysis all samples were centrifuged (6000 rpm, 15 min) and the supernatant was diluted 20 times with 1% Suprapur® HNO₃ (Merck, Germany). Technical details, optimal plasma operating and mass-spectrometer acquisition parameters are available on request.

Serum selenium levels were quantified by inductively coupled mass spectrometry (ICP-MS NexION 350D, Perkin Elmer) using methane for reduction in polyatomic interferences. Calibration standards were prepared by dilution of 10 mg/l Multi-Element Calibration Standard 3 (PerkinElmer Pure Plus, PerkinElmer Life and Analytical Sciences, USA) with reagent blank consisting of 0.65% solution of nitric acid (Suprapur, Merck, Germany) and 0.002% Triton X-100 (PerkinElmer, Tokyo, Japan, USA). Calibration curves were created using four different concentrations: 0.1 μg/L, 0.5 μg/L, 1 μg/L, 2 μg/L. Germanium (PerkinElmer Pure, PerkinElmer Life and Analytical Sciences, USA) was used as an internal standard, and ClinChek^® Plasma Control Level I (Recipe, Munich, Germany) was used as a reference material. Reference material was measured after each of the six samples. If the difference in the reference material measurements was greater than 5%, the entire series was repeated. Each sample was measured in duplicate from different analytical runs. Prior to analysis, all samples were centrifuged (4000 g, 15 min), and the supernatant was diluted 100 times with the reagent blank. Technical details, plasma operating settings and mass spectrometer acquisition parameters are available on request.