Dear colleagues, we are now analyzing fecal samples with the MS but some precipitates occur after the SP3 digestion and elution. We are trying to understand the cause and identify ways to remove them as they harm the LC columns. Thank you for your help and your suggestions.
All the best
Giacomo
Dear Giacomo.
Tell me, what is the composition of the mobile phase you are using?
From what I understand, that the solid is, most likely, salts that are poorly soluble in organic solvents. Try to eliminate them from sample preparation processes, if possible, only perform liquid-liquid extractions or do clean-ups of your extracts in ion exchange resins (e.g., XAD). Alternatively, use acidic (non-buffered) aqueous solutions as mobile phases. Do not use organic solvents such as methanol or acetonitrile.
Best Regards.
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