Fig. 3.

Chromatograms of EDTMP and DTPMP standards in a system with iron contamination. a (A) 10 μM DTPMP, (B) 10 μM EDTMP, (C) 20 μM EDTMP, (D) 20 μM, DTPMP. b (A) 10 μM DTPMP, (B) 10 μM EDTMP, (E) 10 μM EDTMP + 10 μM DTPMP. Chromatographic conditions: column: Thermo Scientific Dionex AS16 (2 × 5 + 2 × 250 mm) at 30 °C; eluents A: 15 mM NaOH, B: 50 mM NaOH + 400 mM NaOAc; flow rate: 0.3 mL/min; gradient profile: 0–6 min 0% B, 6–14 min 10–30% B, 14–18 min 30–100% B, 18–19 min 100% B, 20.1–22 min 0% B, post run: 8 min with 100% eluent A at 0.6 mL/min; detection: amperometric detector with gold WE, Pt CE, and Ag/AgCl RE, 35 °C; waveform: see Fig. 5 (3); injection volume: 50 μL