Sulphate Quantification by Ion Chromatography

The concentration of sulphate was measured by ion chromatography (883 Basic Ion Chromatography plus, Metrohm, Australia) following the modified method of Frankowski (2016) (link). Ground samples were extracted using Milli-Q water (1 g water to 40 g oven-dried tissue) by shaking on a horizontal shaker for 1 h followed by centrifugation at 5.292 g with a swinging-bucket rotor 11150 for 10 min at 20 °C using a Sigma 4K15 table-top centrifuge. Subsequently, 5 mL of supernatant of each extract was filtered through a 0.45-µm hydrophilic syringe filter (Sartorius, Germany) before analysis by ion chromatography. Sulphate anions were separated using a Metrosep A Supp 4–250/4.0 column (Metrohm, Australia) with a 17-min run of an isocratic elution system consisting of 1.7 mmol L⁻¹ sodium bicarbonate (NaHCO₃) and 1.8 mmol L⁻¹ sodium carbonate (Na₂CO₃) at 1 mL min⁻¹ flow rate. For quantification of sulphate, Sigma–Aldrich Multi Anion Standard 1 was used as a standard.