Pinenes

[Red Queen]

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.

[Red Queen]

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

BP_Pinenes2.PNG (90.08 KiB) Viewed 38404 times

[Red Queen]

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.

[Red Queen]

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 (184.66 KiB) Viewed 38286 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 (212.24 KiB) Viewed 38286 times

Dup with Nafion.PNG (192.43 KiB) Viewed 38286 times

Dup no Nafion.PNG (283.53 KiB) Viewed 38286 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.

[Red Queen]

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?

[Red Queen]

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 (189.45 KiB) Viewed 38158 times