Wavy baseline on Agilent GC-MS (5977/7820)

[Oatsandbeans]

I have a problem with a wavy baseline. I am running hydrogen carrier gas, with a method from 150 to 280 degC. The baseline has a regular wave pattern with a cycle time of 1.5 minutes. I have tried column conditioning, changing liners septa, etc. I have just ordered a new big trap for the gas line and a new column to see if that helps. The tune report says there is quite a bit of water in the H2 so I am also drying out the desiccant in the H2 generator. For my work I don't need great signal to noise but that wavy baseline looks funny and it is difficlut ti explain to clients when they ask about it.

[James_Ball]

We were using a hydrogen generator with the desiccant and had a ton of water in the background. We switched to UP hydrogen tanks and everything is clear now. If using a hydrogen generator it is best to use one with the palladium membrane filter to remove the water.

If the instrument was used with helium previously, it will take some time for the background to fall off, seem helium has traces of hydrocarbons in it that will build up on the flow path and hydrogen is a great cleaning agent that pulls it out, so you get a high background for a few weeks after switching.

The wavy baseline is probably because there is a cool spot in the hydrogen pathway somewhere and it builds up then releases over and over causing a wavy background.

[aldehyde]

Please either do a PM on the generator or have a service engineer come look at it / recommend improvements to your setup. What trap did you buy?

Make sure you have an indicating trap. I recommend a big universal trap (https://www.agilent.com/en/products/lab ... rs/gp62792) AND a GC gas clean filter
https://www.agilent.com/store/en_US/Pro ... 88/CP17988

(or equivalent, I don't care who you get it from)

Put the indicating filter after the large trap and replace both once the indicator goes bad. This may seem expensive, but a replacement EPC is more expensive and you will absolutely damage your pressure controller if you allow the generator to hit it with moisture.

Once you have this setup and you regularly maintain the generator you'll never have problems. H2 generators are fantastic, if properly filtered and maintained.