Ionpac as7

The separation and identification of the As species present in fresh plant extracts was performed using HPLC-ICP-MS. An IonPac^®AS7 anion exchange column (Dionex, Sunnyvale, USA) was used for the separation of As species on a 1100 Series HPLC system (Agilent Technologies) coupled to VG PQ EXCELL ICP/MS (Thermo Elemental). A gradient of 0.04 mM HNO₃ and 50 mM HNO_3, (0–5 min, 0%; 5–5.2 min, 0–10%; 5.2–11 min, 10%; 11–11.2 min, 10–100%; 11.2–13 min, 100%; 13–13.2, 100–0.0%; 13.2–18 min, 0.0% of 50 mM HNO₃) was used to elute various inorganic and methylated As species. NIST 1568a rice flour was analyzed for analytical quality Control (total sum of species 279 ± 3 μg kg⁻¹ with 32% iAs and 64% methylated As). Standards of arsenite (sodium arsenite solution, 0.05 M, Merck, Darmstadt, Germany), arsenate (Arsenic standard 1000 mg As L⁻¹ [As₂O₅ in water] Titrisol, Merck), dimethylarsinic acid (cacodylic acid, Alfa Aesar, Karlsruhe, Germany) and methylarsonic acid (Luxembourg Industries (PAMOL) Ltd. Tel-Aviv (Israel)) were used for the identification of As species in plant extracts. For identification of MA^III, it was synthesized by the method of Cullen et al.53 and identified through HPLC-(ICP-MS)/(ESI-Q-TOF-MS) as described in the supplementary information (Supplementary method & Supplementary Fig. S2).

The ICP-MS conditions were summarized as follows: the feedback power at 5 W, the RF power at 1550 W, the flow rate of high-purity argon at 1.00 L·min⁻¹, the flow rate of plasma gas at 15.0 L·min⁻¹, the rotation speed of the peristaltic pump to be 0.2 rps, the detection mass number to be m/z = 75 (As), and the acquisition time to be consistent with that of the liquid phase.
The Agilent 7700 ICP-MS (Agilent Technologies, USA) equipped with an Agilent 1100 HPLC (Agilent Technologies, USA) for chromatographic separations was used to detect and quantify arsenic speciation compounds. Samples were analyzed on a Dionex Ion Pac™AS7 (4 × 250 mm, 5 μm) with a flow rate of 1 mL/min. The mobile phase was 0.025 mol L⁻¹ ammonium dihydrogen phosphate solution (ammonia regulating pH 8.0) (A) and ultrapure water (B), and the gradient elution program is shown in the following table (Table 1).