Seal wash liquid for Thermo Vanquish question

[drewdavis]

I was under the impression that one should use mostly aqueous for seal wash liquids.

But in reading the Thermo Vanquish manual, they call for 75:25:0.1 IPA:water: Formic Acid.

Would some help me with the justification of a high IPA content?

Also why add the acid? I understand why the acid is necessary for a needle wash. But why add it to the seal wash?

[Multidimensional]

A PISTON Seal wash solution should be tailored to the specific applications run on the system. No "Universal" wash solution should be used.

However, here are some guidelines for selecting a PISTON seal wash solution when running RP methods (high aqueous). The goals of a piston seal wash are twofold. (1) To wash away any salt deposits or crystals that may form on the piston(s) during use with buffer solutions. (2) To hydrate and lubricate the seal so that a high pressure seal between the piston and the piston seal is maintained (keep in mind that piston seals are normal wear items). The wash solution should be a mixture containing some organic solvent plus WATER. Methanol and ACN can be used as the organic component. IPA is another great choice as you can use it to maintain the RP pump seals in great condition. It has just the right properties to maintain a good seal plus excellent solubility with NP and RP solvents.Water is the second solution that should be included in the RP Piston seal wash solution. WATER is the ideal solution to dissolve and wash away buffer deposits and crystals. A typical RP Piston Wash Solution should contain enough IPA (or organic solvent) to inhibit the growth of microbes, algea and mold, but also include a high percentage of water so it can dissolve the buffer deposits. No acid is needed and I would avoid it so it does not contaminate your flow path (in case some methods do not use it. Also, FA degrades over a short period of time so serves no purpose if left in a wash bottle for a week or two). We do not know what your mobile phase is so I can not suggest an exact mixture, but something with maybe 50% water and 50% organic may be a good place to start. The higher the buffer conc in the mobile phase, the more pure water you should use (please refer to the article below for more suggestions).

Here is a link to an article on the reasons why you may want to use a PISTON Seal wash system and also what types of solutions should be considered. "HPLC PUMP SEAL WASH & FLUSHING THE HPLC"; https://hplctips.blogspot.com/2012/08/h ... -hplc.html

[per_oxid]

When we run ion chromatography on a waters h-clsss lc i can see each seal wash period as a peak in baseline. Even when system was new so some of the seal wash will penetrate into mobile phase. This amount is probably tiny and i dont see it with uv methods only when using conductivity detector. I dont know if this is something one needs to consider normally but definitely for running an conductivity detector where i set seal wash frequency so it runs after my compound peak.

[Multidimensional]

If you can detect your seal wash solution in your mobile phase, then you have a PISTON SEAL leak. This is abnormal and indicates your pump is overdue for seal replacement. No liquid from the seal wash should be able to leak through the piston seal into the pump chamber. *The seals in the seal wash system (separate from the PISTON seals, which are high pressure) should also be changed on a regular basis too to prevent them from leaking.

NOTE: We have seen seal wash leakage as "normal" in very poor quality HPLC pump designs. Usually these are single piston pumps with cam followers or other early designs (low cost) found on older Waters, SSI, Generic type pumps. It is often wise to REMOVE the seal wash feature on these pumps for a more reliable and less leaky module (manufacturers sell the parts to delete seal wash and restore the pump to a std pump w/o seal wash).

[per_oxid]

In our case it was a brand new H-Class Plus. Conductivity spiked a bit exactly with the set seal wash pump frequency and if we changed frequency the spikes matched. It took me some time to understand thar the baseline ripple matched seal wash settings. Seal wash was 20% acetonitrile 80% water. We dont see any baseline ripple for uv methods just conductivity detector method. I cant say for sure its a leakage just that we got conductivity baseline jump my guess was that it was a tiny amount of wash fluid in the mobile phase. It was also a small ripple but enough to be a problem for quant limit s/n. On our old isocratic pump without seal wash baseline conductivity was very stable. We got the H-class since we mainly run uv detector and this works fine. This experience got me wondering if seal wash selection could be an issue for other methods.

Thanks for the reply I Interpret that seal wash solvent choice usually dont influence the lc method and choice is based on reducing wear of system.

[JI2002]

Formic acid is added to the seal wash solution because a conductivity sensor is used in Vanquish systems to monitor the seal wash solution level in the bottle. When the seal wash solution runs dry, an error message appears to let the operator know to refill the seal wash solution bottle.

[vmu]

Formic acid is added to the seal wash solution because a conductivity sensor is used in Vanquish systems to monitor the seal wash solution level in the bottle. When the seal wash solution runs dry, an error message appears to let the operator know to refill the seal wash solution bottle.

According to the instrument manufacturer, water with 10% methanol has sufficient conductivity for this sensor.
https://assets.thermofisher.com/TFS-Ass ... 405-EN.pdf

[JI2002]

Please read the original post. The seal wash solution is different for VH and VF pump systems.