Chromatography Forum

Hi,

We have a Metrohm 881 IC for anions with both MSM and MCS supressors. About a week ago, an error message popped up and stated that the vacuum is not built up in the MCS and we can hear a strange noise coming out from the instrument. The noise is gone once the MCS is stopped manually. We have re-tighten the vacuum screw at the back of the instrument and the inlet and outlet capillary screws at the front. Does anyone know what is the problem?

Your help is greatly appreciated.

Thanks

Dear vtfchoi

When re-thightening helped and the baseline as well as the backgroud conductivity are back to normal, you may go on.
If a connection is loose, the vacuum pump worked with fulll power. I assume that was the noise you heard.

If the problem appears again, please check with your Metrohm service person.

We have an 881 IC also and sometimes get the same error message. Often if we manually stop the MCS then restart it the vacuum will pump down and all is ok. It may be that the vacuum pump is getting weak or there is a small leak somewhere that does not let it reach operating vacuum fast enough.

Does the problem only happen when restarting after a shutdown?

For ours when we shut down the instrument we leave the vacuum on so that it doesn't have to pump down each day when we restart.

I have got more inforation from our service department.

@vtfchoi

The 881 has an exhaust connection on the back of the instrument. Make sure that this stays open all the time. Otherwise MCS and degasser will not be operaional.
The error message at the start up of the instrument shows that the vacuum build-up is slow. This usually is a sign for leak in the tubings/connections. If this Problem persists, please check with your Metrohm servic person.
Another reason could be that too much air is entering through the air inlet (through the two cartridges. Here it is important that the connecting capillary between CO2 cartidge and instrument is not shortened. If for any reason you had to cut a piece of that capillary, get it replace with the correct length.

@James_Ball
The same applies to your 881. If the error message pops up regulerely after startup, please check with the Metrohm servic person. The MCS will work under these conditions as well but may be not under best conditions.