1,1-DCE by GCMS

[01310040231]

I am having probelm with 1,1-DCE by EPA Method 8260. All the other compouns including gases look great. The values change from run to run. Any suggestions? Thank you.

[Yama001]

I have seen this analyte be fouled up by coelution of water and or methanol from the trap.

This is usually a problem with the earlier eluting gases (bromomethane or chloroethane); I have seen it shift on occasion to a later analyte - changing the trap helped in that case.

You can check this by temporarily setting the scan to 15 to 300, as opposed to the more routine 35 to 300 amu. You can verify where the water and methanol are eluting.

[01310040231]

Thank you very much tjupille for reply.

I did change the trap, but I still have the same problem. I talked to OI and they suggested to use a freshly made trap! They are shipping me a new trap tomorrow. All the other compound, including brominated look great.

[mckrause]

You may have missed the intent of Yama001's response. It's not being caused by the trap - either methanol or water are co-eluting with your 1,1,-DCE. You need to change either your chromatographic conditions or your column.

[01310040231]

Thank you mckrause. You are correct; I did miss the intent and I will look into it.