Non so quale sia la procedura di cui si vanta, ma al momento ho avuto i migliori risultati sciogliendo il chetone in un po' di dcm, riscaldando leggermente a 35-40, aggiungendo la metilammina in una sola volta, lasciando agitare per 10m così com'è e aggiungendo poi il dmso a poco a poco nel corso di 20-30min.L'acqua viene poi aggiunta insieme a un po' di acetato di etile e agitato ancora per qualche minuto, lasciato separare.Diluito con acetone freddo e precipitato, ho provato sia con 33 che con 37,5 HCl, nessuna differenza apprezzabile.
Tra tutte le procedure che ho seguito, questa è stata la più pulita e la più produttiva e, come nota a margine, penso che più grande è la scala e meglio funziona.
Tra tutte le procedure che ho seguito, questa è stata la più pulita e la più produttiva e, come nota a margine, penso che più grande è la scala e meglio funziona.
Great question! When flushing a column in chromatography, the goal is to remove any residual compounds from the stationary phase to ensure a clean system for the next run. The choice of solvent and whether to include water depends on the properties of the solvents used during the chromatography process.
Why Add Solvent Along with Water for Flushing?
1. Solvent-Solvent Compatibility: Many organic solvents (e.g., ethyl acetate, DCM, hexane) are immiscible with water. If water is used alone, it may not effectively remove nonpolar residues. Adding an organic solvent ensures that both hydrophilic (polar) and hydrophobic (nonpolar) residues are washed out.
2. Effective Column Cleaning: If the mobile phase was a mixture of organic solvent and water (e.g., ethyl acetate/water or MeOH/water), using both in the flush prevents precipitation of residual materials, which can clog the column.
3. Preventing Phase Separation Issues: In some cases, a solvent switch from an organic solvent directly to water can lead to phase separation, causing bubbles or irregular flushing. Using a miscible solvent before introducing water ensures smooth transitions.
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If Starting Solvent is Ethyl Acetate (EA) Instead of DCM?
Ethyl acetate (EA) is more polar and water-miscible to some extent, whereas DCM (dichloromethane) is less polar and immiscible with water. The flushing strategy changes depending on the starting solvent:
For EA: Since EA is slightly water-miscible, a water wash alone may work to some extent, but using a mix of EA and water ensures better residue removal.
For DCM: DCM is completely immiscible with water, so a transition solvent (like methanol or ethanol) is often used before adding water.
Practical Approach:
If you used EA as the mobile phase, first flush with EA, then follow with a more polar solvent (e.g., methanol), and finally with water.
If you used DCM, first flush with DCM, then use a bridging solvent (MeOH or IPA) before introducing water.
Hope this helps! Let me know if you need more clarification.
Why Add Solvent Along with Water for Flushing?
1. Solvent-Solvent Compatibility: Many organic solvents (e.g., ethyl acetate, DCM, hexane) are immiscible with water. If water is used alone, it may not effectively remove nonpolar residues. Adding an organic solvent ensures that both hydrophilic (polar) and hydrophobic (nonpolar) residues are washed out.
2. Effective Column Cleaning: If the mobile phase was a mixture of organic solvent and water (e.g., ethyl acetate/water or MeOH/water), using both in the flush prevents precipitation of residual materials, which can clog the column.
3. Preventing Phase Separation Issues: In some cases, a solvent switch from an organic solvent directly to water can lead to phase separation, causing bubbles or irregular flushing. Using a miscible solvent before introducing water ensures smooth transitions.
---
If Starting Solvent is Ethyl Acetate (EA) Instead of DCM?
Ethyl acetate (EA) is more polar and water-miscible to some extent, whereas DCM (dichloromethane) is less polar and immiscible with water. The flushing strategy changes depending on the starting solvent:
For EA: Since EA is slightly water-miscible, a water wash alone may work to some extent, but using a mix of EA and water ensures better residue removal.
For DCM: DCM is completely immiscible with water, so a transition solvent (like methanol or ethanol) is often used before adding water.
Practical Approach:
If you used EA as the mobile phase, first flush with EA, then follow with a more polar solvent (e.g., methanol), and finally with water.
If you used DCM, first flush with DCM, then use a bridging solvent (MeOH or IPA) before introducing water.
Hope this helps! Let me know if you need more clarification.
, appreciate guidance on them. Here we go...