Air leak 5973

One way to test if it is the PFTBA valve is to use a common solvent like dichloromethane and perform a manual tune but look for the ions 49 and/or 84 whislt dropping one drop onto the vent valve next to the PFTBA.

Also check if your PFTBA is empty or not. Quite often when that is running out the EM volts are increased to compensate for the lower PFTBA response and in turn increases the nitrogen/oxygen seen.

Another common area for leaks in the MSD is the MS door O-ring. this may need pushing back into place. But DO NOT put solvent on this part as there are high voltage electrical connections on this section.

Thank you, last week i found the leak in the analyzer door, i cleaned few times the o-ring and N2 decreased to 3 %. However, the EMV increases a lot, very close to 3000 V. I have to change the EM and maybe the ptfba valve.

Check the PFTBA bulb first:

There should be a little liquid in there. If it is empty then that maybe the cause of your high EM volts as it's trying to compensate for low PFTBA concentrations

Yes, It has enough liquid in the PTFBA bulb. The instrument has 12 years old, i dont know when the last time that changes that (I have only 1 year here) and the EM was changed 2 years ago.

Probably, i gonna buy the EM first.

Hello *****,

To check if you have a real leak at the MS, before changing the EM, you have to check the abundance of ion 31 compared to the ion 32, when the PFTBA valve is open.

If 31 is ~70% or more abundant than the 32, your system doesnt have a relevant leak. If 31 is very small  (less than ~ 70%of 32) compared to the 32 then a leak is present.

31 is fragment of the PFTBA, and 32 is obviously O2.

The ratio of 31 and 32 has nothing to do with the age of the EM.

Lets find first the leak.

By the way, it is not a bad idea to have a new EM, ready to be changed when needed, if it has never been changed.

When the leak has been found (can be at the PFTBA valve, by the way), then the decrease of the PFTBA response can be explained by the capillary of the valve being partially blocked. In that case, the valve need to be replaced.

Best regards,

Francisco

Hi,

Looks like you found the leak at the oring. Great job!!!. That's a typical place for a leak especially if you had the shipping screws tightened. I think replacing the EM is a good start. Try rotating your horn 90 degrees. Sometimes it will buy you some time and definitely point in the direction of the horn.