Chromatography Forum

Anybody else having problems with a Teledyne Tekmar Atomx P&T/Conc? Been trying to run a low level direct soil purge calibration and can't get even mildly consistent IS/Surr values in the calibration standards. Benchmark test only revealed that the MFC is not contolling flow as accurate as I would expect as flow is increased. When plotted, curve is a quadratic (flattens out like it was subject to Beers law, I know, that's light but just trying to describe the situation).

I have been having similar problems with surr/IS responses with the Atomx. I don't have any useful advice, but you are not alone!

Jon

How about with aqueous samples? I have analyzed 6 instrument blanks consecutively and the RSD's between the IS/Surr is very low (~2.5%).

Btw, it's nice to know we're not the only lab with an Atomx issue.

hello,

I haven't use it with soils sample. But with aquous clean samples the atomix works fine. This is a purge and trap system then there is some generic problem with water and its addition to the GC/MS system (altough you can reduce it with some tips according to the method requirements: as reduce the desorb time). Morever, in my short experience, it's important to run frequent blanks to check carryover, some compounds are persistent in the system (especially when you run a very concentrated samples), and it's necessary to perform good clean cycles and bakes between samples.

Ricard

Hi, I am the applications lab manager at Tekmar, so I will try to answer this and any other questions you have on the Atomx.

The fact that your water reproducibility is spot on means it is probably not a problem with your internal standard manifold.

There is a slight difference in the reproducibility of soil and water modes for a couple of potential reasons off the top of my head. One, you are sparging in the vial using the 3-stage needle. Depending on your purge parameters (flow and time), this may cause some difference in response versus the fritted sparger used when purging waters. Another potential cause of variance is that you are normally purging 5 mL in a water mode versus 15 mL in soil mode. Depending on the compound (usually heavier), this can cause some slight changes in their purge efficiency.

Can you let me know what IS/Surrogates are you using and what kind of %RSD are you getting? And have you tried spiking the vials manually with your IS and 10mL of water for comparison? Make sure you turn off the IS/water addition in your method if you do this. This could also tell you a lot on what kind of values you should expect.

If you have any data you can provide or any other questions feel free to respond here or email me at nvalentine@teledyne.com.

Nvalentine, thanks for the response. I will try and list the responses from the most current LL soil cal curve. I have them in a spreadsheet for evaluation.

Soil Blank Analysis from 6/4/2012
Cal # PFB (mass 168) Toluene-d8 (mass 98)
1 (0.2) 584773 1885768
2 (0.5) 255722 869011
3 (1.0) 253371 1059682
4 (2.0 286611 919857
5 (5.0) 678126 1978545
6 (10) 671873 956953
7 (20) 340018 1045417
8 (50) 358753 1079881
9 (100) 376958 1075058
10 (200) 834739 2222763
Average 464094.4 1309293.5
Stdev 209319.1 508126.5
%RSD 45.10 38.81

The value is paranthesese is the nominal amount of the standard in ug/Kg. The following is a list of the IS and Surr compounds we use:

Pentafluorobenzene (I)
Chlorobenzene-d5 (I)
1,4-Dichlorobenzene-d4

Dibromofluoromethane (S)
1,4-Difluorobenzene (S)
Toluene-d8 (S)
4-Bromofluorobenzene (S)

I will try to manually inject the IS today and see if that makes a difference. Also, I did check the MFC to make sure it was controlling the gas flow accuately. I found that it varied from the amount requested to measured (digital flowmeter) by >10%. All values are in ml/min and as fiollows:

Atomx flow Actual flow
10.0 10.5
20.0 20.2
50.0 46.7
100 91.4
200 181
300 269
400 356
500 438

I believe that if this was the problem, it would affect water purge as much as soil.

Regards,
Dean Strom

Yeah, that is well outside any normal variance in IS/Surrogate response in soil mode. I ran a soil curve on Friday with the same IS compounds and the %RSDs (by area) over the curve were all about 2.5%.

I do have one question about the data you have provided though. On Cal standard 6, can you verify the response for Toluene-d8 is correct? Everything else seems to be behaving the same for both compounds except that point. Let me know if you can double check the area for toluene-d8 as it doesn't seem to follow the rest.

Hopefully manual injections will help narrow down the issue.

Best Regards,