Gfa ex7i

Shimadzu model AA-6300G® atomic absorption spectrometer (Kyoto, Japan) with the GFA-EX7i graphite furnace atomizer (to vaporize the sample) was used to measure lead and cadmium as described by Subramanian and Meranger [30 (link)]. In brief, heparinised whole blood samples and standards were diluted at a ratio of 1 : 10 with distilled water, and whole blood was then homogenised with 25 ml of 10% triton X-100 (Sigma-Aldrich® Company, Germany). 5 ml of 20% ammonium dihydrogen phosphate (Merck-Darmstadt®, Germany), with 1 ml of concentrated nitric acid (BDH Chemicals®, UK) was then added to the sample, and the volume was titrated to 500 ml with distilled water. The measurement was done at 283 nm and 228 nm for lead and cadmium, respectively. The results were presented as μg/dl.

Calibration blank (Cal Blk) and calibration standard (Cal Std) solutions were prepared at concentrations of 0 μg L⁻¹ (Cal Blk), 4 μg L⁻¹ (Cal Std 1), 12 μg L⁻¹ (Cal Std 2), and 20 μg L⁻¹ (Cal Std 3), using the selenium standard stock solution, or multi-element standard stock solution, into separate 50 mL DigiTUBE^® tubes (SCP SCIENCE, Baie-D’Urfe, QC, Canada) with the addition of 0.5 mL internal standard stock solution, 0.5 mL methanol and 5 mL concentrated nitric acid, and then diluted to the final volume with water. A Shimadzu GFA-EX7i graphite furnace mounted on a Shimadzu model 6300 atomic absorption spectrophotometer was used with a Shimadzu ASC-6100 autosampler. Pyrolytically coated graphite tubes and background correction (D2 lamp) were utilized. Working solutions were prepared by diluting immediately before use standard solutions for absorption a spectroscopy.

The SPAD value (index of total chlorophyll content in a leaf area) of the central parts of the youngest, fully developed leaves (5th to 6th leaves for barley, 4th to 5th leaves for sorghum—the cotyledon was counted as the first leaf) was analyzed using SPAD-502 (Minolta, Osaka, Japan). Chlorophylls were quantified after extraction with 80% (v/v) acetone [51 (link)].
Fe concentration was measured using an atomic absorption spectrometer (AA-6300, Shimadzu, Tokyo, Japan) coupled with a graphite furnace atomizer (GFA-EX7i, Shimadzu) after the digestion of leaf materials, as described previously [13 (link)]. To determine trace Fe in thylakoid membranes (Figure 2C), extremely clean reagents, instruments, and atmosphere were prepared. Digestion was performed with Teflon tubes (perfluoroalkoxy alkanes (PFA) sample test tube, T43-012, Matsuura-Seisakusho Co. Ltd., Tokushima, Japan), which release no Fe when heated with HNO₃. All Teflon tubes and plastic tips with filters were soaked in diluted HNO₃ before use. The bench was covered with a simple household greenhouse composed of steel pipes and a plastic cloth.