Table 1.
Elution gradient selected for the different stationary phases.
| Stationary phases | Nature of stationary phases | Elution gradient |
|---|---|---|
| Unitary XAmide | Amide-bonded silica | 0–15 min/17% B, 20–30 min/23% B, 40 min/50% B. |
| Cosmosil 5X-SIL | Bare silica | 0–15 min/12% B, 20 min/20% B, 30 min/40% B, 35–45 min/50% B. |
| ZORBAX RX-SIL | Bare silica | 0 min/20% B, 20 min/40% B, 35–45 min/50% B. |
| Venusil HILIC | Amide-bonded silica | 0 min/15% B, 35 min/30% B, 45 min/45% B. |
| Unitary Diol | Propanediol-bonded silica | 0 min/15% B, 35 min/30% B, 45 min/45% B. |
| Venusil NP | Nitrobenzamide-bonded silica | 0 min/15% B, 35 min/25% B, 45 min/45% B. |
| Venusil PFP | Pentafluorophenyl- bonded silica | 0 min/5% B, 10 min/35% B, 30 min/45% B, 50 min/50% B. |
| ZORBAX C18 | Octadecylsiloxane-bonded silica | 0 min/15% B, 15 min/30% B, 30–40 min/50% B. |
| Unitary NH2 | Amino-bonded silica | 0 min/20% B, 40 min/30% B, 50 min/45% B. |
| Venusil Imidazolyl | Imidazole-bonded silica | 0 min/5% B, 10 min/15% B, 20 min/25% B, 40 min/50% B. |
Conditions: mobile phase: (A) sCO2; (B) MeOH containing 5 mM ammonium acetate, 0.4% (v/v) TFA and 5% (v/v) water; temperature: 25 °C; backpressure: 140 bar; flow rate: 3 mL/min; make-up solvent: MeOH (containing 5 mM ammonium acetate); flow rate of make-up solvent: 0.3 mL/min; injection volume: 5 μL.