High 1,1-Dichloroethene Recovery

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

4 posts Page 1 of 1
Hello,

I'm running EPA 524.2 by purge and trap on a Agilent 5977/7890 with an OI Eclipse 4760.

Our 1,1-Dichloroethene recovery was individually higher than all the other analytes in a recent PE sample.

In the past this has been traced back to the breakdown of 1,1,1-Trichloroethane to 1,1-Dichloroethene in the #10 trap we use, but the breakdown of our current trap is around 2% and since 111-TCA was spiked low in the PE it does not account for very much of the increase.

I was thinking that, perhaps there was some degradation in our calibration standard of 1,1-DCE due to it being mixed with everything else (gas oxygenates, keytones, ...) but I could not find any chemistry that made sense.

To test it anyways I left a mixed standard sealed out at room temperature for a few weeks. 1,1-DCE did not degrade when compared to a paired standard stored at -20c.

Does anyone have any ideas of what could be causing this?

Thank you for any help you can provide.
DReggio wrote:
Hello,

I'm running EPA 524.2 by purge and trap on a Agilent 5977/7890 with an OI Eclipse 4760.

Our 1,1-Dichloroethene recovery was individually higher than all the other analytes in a recent PE sample.

In the past this has been traced back to the breakdown of 1,1,1-Trichloroethane to 1,1-Dichloroethene in the #10 trap we use, but the breakdown of our current trap is around 2% and since 111-TCA was spiked low in the PE it does not account for very much of the increase.

I was thinking that, perhaps there was some degradation in our calibration standard of 1,1-DCE due to it being mixed with everything else (gas oxygenates, keytones, ...) but I could not find any chemistry that made sense.

To test it anyways I left a mixed standard sealed out at room temperature for a few weeks. 1,1-DCE did not degrade when compared to a paired standard stored at -20c.

Does anyone have any ideas of what could be causing this?

Thank you for any help you can provide.


Could Tetrachloroethane have broken down loosing two chlorines to Dichloroethene?

The worst I always had to deal with was Pentachloroethane breaking down to Tetrachloroethene, but we switched to a chilled autosampler and keeping the samples at 5-10C helps that a lot. The Haloalkenes are usually quite stable in these standards, the Haloalkanes have always been the problems.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:

Could Tetrachloroethane have broken down loosing two chlorines to Dichloroethene?

The worst I always had to deal with was Pentachloroethane breaking down to Tetrachloroethene, but we switched to a chilled autosampler and keeping the samples at 5-10C helps that a lot. The Haloalkenes are usually quite stable in these standards, the Haloalkanes have always been the problems.


Thanks James,

Everything else in the PE sample was spot on, leading me to thing that if it was standard breakdown it would have been of 1,1-DCE in the calibration standard.

On the off chance that an odd coelution happened to occur I switched the quantitation ion but that resulted in similar results.
We were having the same problem. The peak shape for 1,1,DCE did not look good (brand new 4760 and trap). This was done with desorb preheat ON (OI's suggestion). When we calibrated with desorb preheat OFF; 1,1-DCE looks perfect. Were you able to resolve this issue?
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