Table 2 Common eluent additives for RPLC–ESI–HRMS screening methods
From: NORMAN guidance on suspect and non-target screening in environmental monitoring
Additive | pKa (at 25 °C in water) | Buffer region | Typical concentrations |
|---|---|---|---|
Formic acid | 3.75 | – | 2.6–26 mM (0.01–0.1%) |
Ammonium formate | 3.75 9.25 | 2.8–4.8 8.3–10.3 | 1–5 (10) mM |
Acetic acid | 4.76 | – | 1.8–18 mM (0.01–0.1%) |
Ammonium acetate | 4.76 9.25 | 3.8–5.8 8.3–10.3 | 1–5 (10) mM |
Ammonium hydrogen carbonate | 6.35 (H2CO3/HCO3−) 9.25 (NH4+/NH3) 10.33 (HCO3−/CO32−) | 5.4–7.4 8.3–11.3 | 1–5 mM |
Ammonia | 9.25 | – | 5–10 mM |
Ammonium fluoride | – | – | 0.1–1 mM |