Asrs 300 4 mm suppressor

The total concentration of Al in organs (Al/total; air-dried at 60°C and stainless-steel milled) was determined by ICP-OES after microwave assisted high pressure acid-digestion (65% HNO₃:30% H₂O₂ 4:1). Certified reference material (CTA-OTL-1 oriental tobacco leaves) was mineralised under the same conditions for quality assurance. The concentration of Al in organ infusions (Al/infusion) was determined by ICP-OES after leaching (15 min) and filtering of the suspension of organ biomass and boiled deionised water (1/50, w/v) [41 (link)] through filtration paper ‘Filtrak 390’ (Niederschlag, Germany) with porosity 3–5 μm and flow rate 0.1 ml/s [DIN 53137]. After filtration through a 0.45-μm nylon membrane filter, concentrations of low-molecular-weight organic acid (LMWOAs; acetate, citrate, formate, lactate, malate, maleate, propionate, tartrate, and oxalate) anions in the same organ infusions were determined by means of ion-exchange chromatography with suppressed conductivity. An ion chromatograph ICS 1600 (Dionex, USA) equipped with IonPac AS11-HC (Dionex, USA) guard and analytical columns was used. The eluent composition was 1–37.5 mM KOH with a gradient of 1–50 min; and flow rate was set to 1 mL/min. To suppress eluent conductivity an ASRS 300–4 mm suppressor (Dionex, USA) and Carbonate Removal Device 200 (Dionex, USA) were used.

Sulfur contents in all extracts were determined (detection limit 0.5 µg L⁻¹) by ICP-MS (Element XR, Thermo Scientific, Waltham, MA, USA) operated in medium mass resolution, applying external calibration and internal normalization (In and Sb, both single element ICP standards). However, given amounts of HCE (sulfate-S) throughout the paper were determined (detection limit 0.1 mg L⁻¹) by means of ion-exchange chromatography (IC; ICS 1600, Dionex, USA) with suppressed conductivity, applying the IonPac AS11-HC (Dionex, USA) guard and analytical columns, and the ASRS 300-4 mm suppressor (Dionex, USA). 30 mmol L⁻¹ KOH was used as the effluent (flow rate 1 mL min⁻¹).