Chromatography Forum

I am trying to run 50:1 DI:MeOH soil samples on my Atomx. I am seeing an effect with 11DCE where it is suppressed 4/5 times. I know that the compound is right inside the MeOH Retention time area. How can I separate these two? How can I reduce the effect? Anyone else have luck running MeOH prepped soils on the Atomx?

Hi Michelle,

Can I ask what scan range you are using for your methanol extractions? And what column are you using for this analysis?

Most of the work using this technique is performed on BTEX/GRO compounds, so I'll have to see if we have any data on a full 8260 list.

I am using a 30m Restek RTX-VMS column 30x250x1.4
Scan range is 35 to 280, threshhold 175, sampling 2.
I think this is what you want to know.

I'm not sure that coelution is the cause of the low response. I was assuming this was merely a separation issue, but it may be tied to the extraction.

My concern is that 1,1-dichloroethene might be simply too volatile to run an automated methanol extraction. It is really the first compound after the normal 502.2 gases.

When you perform a methanol extraction on the Atomx, it will add the methanol on top of the soil, then there is a mix/equilibration time where the 11DCE may be working its way into the headspace due to its volatility.

I am not performing an automated meoh extraction. I am prepping the 50/1 dilutions at the bench and running the samples in "water" mode.

I have lighter compounds in my VOC mix (vinyl chloride, Cl2f2ch3, etc..) These compounds are working fine. When I have had problems with 11DCE in the past, it was because of a timed event at that RT. This system has no timed event. The only thing I can think of is the MeOH interaction since I know it lands at that RT.

It is very strange that this happens intermittently. I am also using a Velocity and a 3100 and do not have this problem.

I'm going to run some standards without MeOH and see how they look.

I apologize for the confusion.

Would it be possible to get chromatograms that demonstrate the issue? Also, if I could get the conditions for both set ups that would be great. My email address is nvalentine@teledyne.com.

Unless something is significantly different, like the trap type, we should be able to get similar performance through some method modifications. There are some slight design differences that may be contributing, but hopefully we can address them and make it apples to apples with your other systems.

Best Regards,

I just emailed instrument methods and P&T methods. The other two instruments use a K trap. We currently have a #9 trap in the Atomx.

I had an instrument that behaved like this until I put a new trap in. The old trap was fine unless we were doing medium levels, with the excessive methanol. In that case it was also the Tenax/Silica/CMS type.

Thanks Yama. I made changes to my soil mount temp - per Nathan's advice..... and it is looking better. I guess it was a little too hot. The trap I have is definitely questionable as well.