Detailed description of analytical methods
Sample cleanup |
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| Cartridge | C18; 100 mg/l ml; International Sorbent Technology, Great Britain |
| Buffer A | Aqueous solution of 150 mM ammonium acetate, pH 4.5 (acetic acid) |
| Buffer B | Aqueous solution of 15 mM ammonium acetate, pH 4.5 (acetic acid) |
| Liquid chromatography | |
| Eluent A | 15 mM ammonium acetate, water/acetonitrile (9:1), pH 4.2 (formic acid) |
| Eluent B | 15 mM ammonium acetate, water/acetonitrile (1:9), pH 4.2 (formic acid) |
| Flow | 0.5 ml/min, post-column split 1:10 |
| Gradient program | B: linear increase from 25 to 40% in 11 min, 90% for 2 min, 3 min equilibration |
| Column | Purospher RP-18; 125 × 3 mm, particle size 5 μm, end-capped |
| Injection | 5 μl |
| Mass spectrometry | |
| Ionspray voltage | 5500 V, positive ion mode electrospray |
| Orifice voltage | 20 V |
| Nebulizing gas | Purified air, 0.82 l/min, Atlas Copco, Belgium |
| Curtain gas | Nitrogen, 0.95 l/min, Generator system 75-72, Whatman (Clifton, NJ) |
| Collision gas | Nitrogen, generator system 75-72, Whatman |
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Turbo gas
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Nitrogen, 6 l/min, 350°C, Generator system 75-72, Whatman
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