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- Posts: 39
- Joined: Wed Oct 15, 2014 2:55 pm
- Location: New York
The problem happens randomly regardless of analyst, PPM, turbovap, etc. and happens to controls as well as samples. We adjust the pH to 6 prior to adding to the SPE column. We have collected the sample load, methanol wash, and water wash and see no breakthrough. An extra aliquot of elution solvent (MeCl/IPA/NH4OH 78/20/2) shows no extra being retained after elution. We have been unable to force a failure by playing with flow rates. In controls we will see a large drop in nalorphine with little to no drop in other drugs, so it seems to be specific to nalorphine. It is very sporadic and the drop amount is inconsistent. We are being extra careful about spiking the IS. Can anyone shed some light on what might be happening? We are working on a new method with deuterated IS but need to fix this in the meantime. I can share more specifics about the method if needed.