Chromatography Forum

Dear All,

I have been working with a LCQ Deca Xp Plus coupled with Ultimate Plus pump and Famos autosampler.

Since Friday, I have high pressure problems and I can not run anything with a flow rate above 5ul/min coming from the HPLC.

The day before, I have infused to the MS a very cloudy sample but I have clean the sample transfer line and the ESI right after that. I have this high pressure since then, therefore, I think it is related.

The strange thing for those who work with the HPLC Ultimate is that I can not set manually a flow rate above 50ul/min. I have a high pressure error message and the pump stops.

I think the ESI needle is partially blocked and I have flushed it with methanol and water 50:50 at 5ul/min (with the HPLC) for half a day. What else can I try? Any ideas?

Many thanks to all...

Have you tried to look at the pressure without the MS coupled to the HPLC?

Hi Tomtotom,

I don't have a readack value of the pressure while using only the MS, but I can easily see that there is a leak at the end of the syringe when I infused MeOH directly into the MS at 10ul/min. At 5ul/min, there is no leak.

I believe you have already come to the right comclusion.. The Probe is blocked somehow.. If flushing does not solve the high back pressure you need to renovate the probe( Exchange metal needle/fused Silica and maybe dismantle probe completely and sonicate all parts in MeOH and or H2O..

BTW: If you sample is cloudy your first thought should not be "lets put this is the MS".. That is asking for trouble!

Leadazide,

Indeed, I am afraid I have to disassemble the probe and clean it thoroughly.

The sample I analysed few days ago was filtered twice (0.45um filters) before infusion. The sample was still cloudy but I assumed (wrongly now) that it should be fine. I immediately flush the sample transfer line after analysis and did not use the MS until today.

Many thanks for the partcipation