Sampling in the Laurentides

It was the last trip of the year – I went sampling to Parc Tremblant, which is about a 2 1/2 hour drive north of Montreal. The snow water content was already very high and the metamorphism of the snow advanced. Snow temperature was almost uniform in the first 15 cm. There is not snowmobiliing the park during winter, so pollutants should be considerably reduced. Additionally, it is far from larger cities and there is not much to the West either.

The weather was great and I had no problems sampling at 5 different spots in the park (40 samples in total). Only a few trails were open due to the melting season, but it was enough for me. I have sampled up a mountain (about 250 m up from Lac Monroe and near a smaller lake (Lac-des-Femmes). I am now pretty confident in using my protocol, so everything went smoothly. I hope to get additional meteorological data from Tremblant, which is the next Environment Canada meteorological station.

After a long day, I was able to bring my samples back to the lab still frozen and in original state, where I put them into a freezer immediately. Nice. So – with the last samples coming in from Alaska this week, my collection will be complete; I have more than enough to do over the summer.

So – where is the error?

After a cold kept me from doing work for a while, I am now checking the GC-MS for VOC sensitivity. From my last experiments I have learned that the purge time limit, when running in “splitless” mode, needs to be optimised (for some reason it was set to zero). I am getting a good signal, when I purge 5 min after injection (but that also leaves me with a lot of water in the system). So I am optimising the time of purging (after 30 sec, 1 min, 2 min,…) to find out the best time.

I am also preparing another (last) sampling trip for the beginning of next week. I hope to find some more snow on the northern slopes of the Laurentides, north of Montreal. In the city, most of the snow is gone now. Sampling in Alaska, which is done by Samuel Morin (thanks!) is also going well. I hope I am able to get that UPS account number that I have applied for a week ago soon, so that shipping back is not a problem.

Sampling at Mont Saint Hilaire

Last Friday I was off sampling with my “reduced” samping kit. I went to Mont Saint Hilaire, a McGill University research station and nature park, about a 45 min drive east of Montreal.

Sampling went really well and it was a great day out. I have taken 21 samples (including 3 blanks) at three different locations:
* 4.9 km from the parking lot on the top of the mountain (approx 12.30)
* 2.6 km from the parking lot in a little valley (approx 14.00)
* on the parking lot (approx 15.20)

The weather was perfect for a little hike and I packed all my sampling gear into my backpack (including some ice packs) and off I went. All samples returned frozen to the parking lot, where I put them into a large cooler with additional ice packs and snow. Everything was still frozen upon my return to the lab đŸ™‚

All together, sampling – if done properly – takes a while, so I had to postpone my afternoon trip to the Laurentides, but it was worth it that I took the time to do everything properly and as clean as possible.

Well – now I am confused …

I have put in a long night in the lab and I have measured some of the samples that I have collected recently on McGill campus. I was expecting a number of compounds, but instead I got … nothing.

I am quite confused. The GC-MS system is in excellent shape. The baseline is low and column bleeding is at a minimum (should that worry me?). The recent servicing (which was 2 days of work) paid off. Additionally, Farhad has switched the filament as well – so everything should be ok.

But what makes me really suspicious is that I have doped one of the samples with Chlorobenzene-d5, and I have not found it (not a single fragment!). Only a large amount of a EtOH-Toluene mixture showed up in the TIC. Next day a colleague told me that he had some problems too, but solved them by checking the injector and tightening all screws. Well, I will make sure everything is fine there next time and run a control sample.

Ready to go sampling

As winter is slowly coming to an end, I am ready to collect new samples for the last time. Together with the ongoing Alaska campaign (I expect samples to be back at the end of April), I have enough to analyze during summer. With my new sampling and storage, I hope to minimize my analytical error.

The campaign will take me outside Montreal to Mont St. Hilaire and the Laurentides. I would like to sample in forested areas for biogenic compounds and I am also looking for less anthropogenic influence. Most of my equipment is already in Barrow, so I will not do any depth-profiling, but bulk-sampling should be possible.

(Internal) standard list

My list with standards is ready. I have checked my earlier data for the most common organohalide and aromatic species. I have come up with a total of 22 species. Everything is ready to order (order no, CAS no, …).

Additionally, I have identified four potential internal standards (in addition to chlorobenzenze-d5, which I have already tested: fluorobenzene, 1-chloro-2-fluorobenzene, 2-bromo-1-chlorobenzene and bromo-chloromethane).

These standards will enable me to establish external calibration curves for my species (in the liquid phase and the headspace) and I will be able to test the potential internal standards for their ability to accurately quantify my analytes in my snow samples. If it works out, future quantification will be easier and cheaper.

Internal standard decision

Well, after a lot of reading in the past few days, I have come to the conclusion that there is/are no internal standard that is/are well documented enough to work with my set-up. Therefore, I will test a number of them for suitability with the compounds that I find in the snow.

That means setting up calibration curves for the pure analytes found in my samples and matching them with my internal standard(s). That is going to take a while, but at least the quantification process is going to be well documented.

New snow samples collected

I went out on campus today to collect some new snow samples. Most of my sampling equipment is still in Alaska, but I have tried my best anyway to work as clean as possible.

I have taken 3 blanks, 4 samples in pre-cleaned amber glass bottles and 8 samples in sterilised HDPE bottles. Sampling went well and I have taken snow from 2 different strata (0-2 cm and 2-7 cm). I have put them in the frezzer right away – so everything should be fine until analysis.

I hope to drive out to the countryside next week. I would like to collect samples that are less polluted and some in a forested area, so that I can see some biogenic compounds as well.

Searching for internal standards

For a while now I have been trying to find a good source for suitable internal standards for VOC quantification using GC-MS. For aromatics I was able to come up with chlorobenzene-d5 from an EPA paper and it turned out to work pretty well for some of the aromatics that I found in my snow samples.

For the organo-halides, the situation seems more difficult. I have managed to come up with with a bunch of compounds (e.g. fluorobenzene, bromo-chloromethane, 2-bromo-1-chloro-propane), but it is difficult to find a list of the analytes that they can quantify. My searches for papers using these compounds as IS has not been too successful either.

Well, if I can not come up with a reliable source soon, I will start trying myself and see, if they work with the halogenated compounds that I have found in my snow samples (e.g. diiodomethane, chloroform, dibromomethane).

Getting the GC-MS going again

I thought that I would start measuring snow samples again, but the GC-MS let me down. I have not measured any samples since I got back from christmas vacation and it seems that there was a bit of junk that got built up in the system. So I was back to a little cleaning exercise. But I got the job done. After a liner change and some good column baking the baseline was a lot better than before and bleeding has almost stopped. However I still have some diethylphtalate contamination consistently showing up at 15.5 min. I am still guessing, what the source could be.

Anyway – I am (and even more important: the GC-MS is) ready to get some snow measurements done!