I am analyzing complex samples by Acquity UPC2 coupled to HRMS and I am having trouble with the carry-over effect of polar compounds - sugars. I´ve tried changing the initial wash solvent (MeOH/IPA 1:1) to more polar one (MeOH/H20 up to 1:1) and increased its volume without any success. Anything else I can do?
Hi Michaela, by initial wash solvent do you mean the make-up flow for the MS?
For SFC-MS some times the carry over issue may arise from precipitation of analytes in the MS interface. What is the composition of your make-up solvent and what's the flow rate?
Wouldn´t there be retention time shifts in such case?
I use MeOH with 0.1% HCOOH or with 2mM HCOONH4 at a flow rate of 0.25 mL/min. The modifier is MeOH/MeCN 80/20 with 15mM HCOONH4 or with 0.15% HCOOH, its highest ratio in the mobile phase (the flow rate 1.8 ml/min) is 40 %. I had the same problem with the modifier with additional 5 % water and different column chemistries.
Instead of Acetic Acid try Formic Acid instead. You might get lucky. If I recall my sugar/starch chemistry (~40 years ago) you may be modifying them by forming acetates.
You are right - I overlooked the results you uploaded. Can you check with lesser polar compounds and see if the problem persists?
You may try going up to 100% water as strong wash and and IPA for weak wash.
Also, can you conduct a wash syringe leak test? If it's leaking you may have similar issues.
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