Does anyone have any tips on clearing blocked nanoViper (20 uM ID) tubing in a Dionex 3000 for LC-MS/MS? We're having recurring high pressure errors in our loading pump, and we've isolated it to a specific piece of nanoViper tubing between the loading pump and autosampler. The chemical identity of the clog is unknown, only that it is from a sample and is hydrophobic. Obviously identifying the source of the contaminant is important, we are investigating that as well. The pressure is excessively high but the flow is not completely blocked.
Currently we've connected the tubing directly to the loading pump, with the opposite end open. We have run first water and now 75% ACN through it, in both directions, but with little success in dissolving the block and reducing the pressure so far. Would a stronger/different solvent be useful?
If you are certain the clog is of hydrophobic nature, and your system is capable of handling it - Tetrahydrofuran is probably a good option. If you are unsure if your system can handle 100%, perhaps a 1:1 mixture of THF/Acetonitrile can already make a difference.
In the past, I have encountered some issues where a compound in the acetonitrile clogged my pump valve due to buildup of material there. Was neither soluble in water or in acetonitrile (or mixtures) but an overnight flush with ethanol solved that issue.
No guarantee that either will work, but perhaps worth a try.
Tubing is a consumable. Replace it.
The real problem is the particulate contaminants in the sample. Filter or centrifuge your sample. Review your sample prep.
ACN is a poor choice as a 'wash solvent' for most methods. You need to use a wash solution (and perhaps a mobile phase too) that will fully (fully = 100%) dissolve the types of compounds you are running through this instrument. *This is a basic fundamental of training in the use of the system.
As you stated, FIND the cause of the clog first. Maybe you are overloading the system with sample? Maybe it is not fully soluble in the solution or when it mixes with mobile phase, it falls out of solution. This is clearly a training issue. In the meantime, replace the clogged tubing with fresh new tubing (tubing is cheap vs the time and solvents spent trying to clean it). Dissolve all samples in an appropriate mobile phase (one that they dissolve it). FILTER all samples with a chemically compatible filter before injecting. Insure that your HPLC method and mobile phase choices are appropriate for the samples (do they dissolve fully in the mobile phase?). Make sure you include a separate column Wash "step" after each run (this should be programmed as a 'Wash method" to be run after your analysis method). The "Column Wash" should utilize solvent mixtures that are fully compatible with your column and detector AND which are stronger than your mobile phase so they wash any potential late eluters or matrix off the column and out of the HPLC system and detector BEFORE the next analysis. Again, ACN is a very poor choice. Select solvents which will dissolve your materials and use a gradient during the wash.
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