Pinenes

General discussion of factors that affect chromatographic resolution, peak shape, and noise in the raw data.
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Red Queen
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Pinenes

Post by Red Queen » Sat May 27, 2017 9:55 am

The new 2017 PAMS retention time standard has shipped from Linde. This standard was analyzed by ERG to confirm concentrations and I have attached the Certificate of Analysis from the batch here. At this week’s PAMS AutoGC workgroup conference call there was some discussion on the identification of the three newest targets, 1,3-butadiene, α-pinene and β-pinene. The folks from NY reported that α-pinene was eluting between isopropylbenzene and n-propylbenzene and β-pinene between 1,2,4-trimethylbenzene and o-ethyltoluene. We did not get the same results although columns and traps may be different. In addition, our sample is from a trans-fill into a canister provided from TCEQ so based on discussion of the degradation of the β-pinenes it is possible it is not in this canister. Since it may be a factor I will mention that we see some differences in the resolution on the PE systems and the Markes system which is due to the difference in the trap dimensions. The trap in the Markes system is a smaller bore and thus gives a sharper initial injection into the columns so you may require more outlet split to achieve better resolution which could raise detection limits.
Attachments
2017 EPA PAMS 1411421-BatchCert_1-3pgs.pdf
2017 PAMS Standard Linde Batch C of A
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Off with their heads! _________________________________________________________________

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Red Queen
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Re: Pinenes

Post by Red Queen » Tue May 30, 2017 2:23 pm

I have run a canister on both the Markes system and the PerkinElmer and I can only see one peak which is not fully resolved after 1,2,3-trimethylbenzene. When I calculate recoveries from theoretical values from ERG I get good results with the exception of m-ethyltoluene which is at 120% which makes me suspect that the other pinene is co-eluted with this peak. We are going to run this sample on the GC-TOF instrument to see if we can sort this out since both of our AutoGCs have nafion driers.
Markes Unity CC496196
Markes Unity CC496196
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Red Queen
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Re: Pinenes

Post by Red Queen » Wed May 31, 2017 4:07 pm

Well, got the results from the TOF analysis and both a and b-pinene are indeed in the can. The analysis was done on a 624 Column so the retention times won't match but a-pinene came out near isopropylbenzene and b-pinene between 1,3,5 trimethylbenzene and one of the ethyltoluenes. Pretty good sensitivity for a direct injection of nominally 2 ppbv.
Off with their heads! _________________________________________________________________

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Red Queen
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Re: Pinenes

Post by Red Queen » Sat Jun 03, 2017 1:27 pm

We have done some more work on trying to identify the pinenes in the new PAMS standard. After determining by TOFMS that they were indeed in the canister, we collected the new standard on our Markes system at 30°C without the Nafion® drier in line and got some interesting results. The peak after 1,2,3-trimethylbenzene which we believe is β-pinene was half the amount seen when run with the Nafion® inline and there were a number of new peaks in evidence.
Pinenes no nafion.PNG
Pinenes no nafion.PNG (184.66 KiB) Viewed 17272 times
Fearing that we may have done something wrong or that the system now had contributions which were not there before, we also ran a blank without the Nafion® drier. The additional peaks could not be accounted for so we put the Nafion® back in line and confirmed our original analysis and the pinenes after 1,2,3-trimethylbenzene reappeared at the original concentration and the unknown peaks disappeared. We then ran once more without the Nafion® to verify that is was clearly the system modifying the pinenes.
Pinenes compare.PNG
Pinenes compare.PNG (212.24 KiB) Viewed 17272 times
Dup with Nafion.PNG
Dup with Nafion.PNG (192.43 KiB) Viewed 17272 times
Dup no Nafion.PNG
Dup no Nafion.PNG (283.53 KiB) Viewed 17272 times
Based on previous experiences with isoprene we relate this to possible reactions with moisture on the trap either during sampling or at desorb. While we did do a dry purge after sampling we did not make any effort to optimize the dry purge and in reality it was short.
Off with their heads! _________________________________________________________________

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Red Queen
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Re: Pinenes

Post by Red Queen » Mon Jul 10, 2017 12:30 am

We are participating in a field demonstration of the Markes UnityXR with a Kori at the South Coast AQMD Rubidoux site for a month. We have preliminary chromatographic results but the retention times for the pinenes are not exactly what has been reported. Initially we were using the Markes T17 trap which is a graphitized carbon material and we only saw one peak eluting between iso and n-propylbenzene which we assume is a-pinene. We put the same SGE BP1 column (50m x 0.22mm) we are using at the Rubidoux site into our GC/TOFMS again and could clearly see both pinenes run neat eluting well separated with a-pinene between iso and n-propylbenzene and b-pinene between o-ethyltoluene and 1,2,4-trimethylbenzene and quite well separated. We got the preferred T20 trap installed and now are getting one peak between iso and n-propylbenzene but the second peak is co-eluting with o-ethyltoluene. It is only 50% resolved and flow adjustments failed to increase this separation significantly. In reviewing the data I have that has been reported it has all been done by GC/MS and I am wondering if anyone has and GC/FID data. I believe perhaps there may be a significant vacuum effect which is affecting the separation reported by others. Does anyone have any experience with their new PAMS standard on GC/FID?
Off with their heads! _________________________________________________________________

In God we trust, all others must bring data.
W. Edwards Demming

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Red Queen
Posts: 17
Joined: Tue Dec 08, 2015 11:31 am

Re: Pinenes

Post by Red Queen » Mon Jul 10, 2017 12:35 am

We are participating in a field demonstration of the Markes UnityXR with a Kori at the South Coast AQMD Rubidoux site for a month. We have preliminary chromatographic results but the retention times for the pinenes are not exactly what has been reported. Initially we were using the Markes T17 trap which is a graphitized carbon material and we only saw one peak eluting between iso and n-propylbenzene which we assume is a-pinene. We put the same SGE BP1 column (50m x 0.22mm) we are using at the Rubidoux site into our GC/TOFMS again and could clearly see both pinenes run neat eluting well separated with a-pinene between iso and n-propylbenzene and b-pinene between o-ethyltoluene and 1,2,4-trimethylbenzene and quite well separated. We got the preferred T20 trap installed and now are getting one peak between iso and n-propylbenzene but the second peak is co-eluting with o-ethyltoluene. It is only 50% resolved and flow adjustments failed to increase this separation significantly. In reviewing the data I have that has been reported it has all been done by GC/MS and I am wondering if anyone has and GC/FID data. I believe perhaps there may be a significant vacuum effect which is affecting the separation reported by others. Does anyone have any experience with their new PAMS standard on GC/FID?
SCAQMD_T20_Pinenes.PNG
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Off with their heads! _________________________________________________________________

In God we trust, all others must bring data.
W. Edwards Demming

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