Does anyone have the part number for Thermo’s “OD 1/8 inch [0.8 m; molesieve?] column” for the EA-Isolink described in the thread below? I was told by a Thermo engineer that the part number listed in the manual (260 08243) may be inaccurate; moreover, no vendors seem to offer it. We have one such column currently installed in our system, but unfortunately its P/N identification tag was charred after the first bake out.
Thanks in advance!
p.s. @ NJ (New Taipei City) I would have contacted you directly but your contact details are hidden, for me at least.
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Thermo uses new design “OD 1/8 ench column” on EA isolink. So the N2 and CO separation shall be better than TC/EA or Flash HT. I have use the same column on Flash HT, the separation is as well as EA Isolink.
I also have tried Temperature from 1350 to 1450, 1450 has low or none signal between N2 and CO on TCD but very high back ground on mass 28 29 30 on EA isolink system. In my case, I am trying better parameters for d18O calibration to silver tube water STDs. I am very appreciate if anyone have good ideas.
Btw because of different design of the machines between EA isolink and Flash HT, this column type has very bed performance for dD analysis on Flash HT in my experience.
Stable Isotope Geochemistry <[log in to unmask]>
代表 Wolfram Meier-Augenstein
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主旨: Re: [ISOGEOCHEM] [External] [ISOGEOCHEM] N2-CO peak separation tips
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Good point. I just thought given you are analysing proteins the peak on far left of your TCD trace is a tad small for an H2 peak.
I was also reading across using our TC/EA-IRMS runs of hair. On our system N2 typically was separated from CO by about 80s peak to peak (ca. 10s peak end to peak start). A difference of 65s as in your case therefore seemed to be in the right ballpark.
Anyhow, let’s say the peak at 101s is H2 and the hump is N2. In this case, you could try dropping the GC temperature to 80°C and see if this improves matters. Failing that, a combination of GC temp and a slight increase in He flow might do the trick. I noticed the CO peak is a tad on the wide side (>>50s). Before tweaking the GC conditions, it is probably not a bad idea to bake out the GC column as Wan suggested.
Failing all that, trading up to a longer GC column might be in order. J
One comment on the mass traces. You are right, NO has mass 30 which is why I was wondering if could be HCN (27; 28; 29).
Cheers Wolfram for those papers! We're currently running with just glassy carbon chips... no Cr. I was under the impression that the left peak on my TCD was H2, and the middle hump was N, but it sounds like it could potentially be something more exotic. Here's a closer image of the measurement, which is USGS Tibetan Hair by the way. Note that the m/z=30 trace is relatively flat, compared with 28 and 29. This made me think this was my N2 peak...
Quality of separation can only be achieved by better chromatography which may mean tweaking GC conditions (carrier flow; column temperature) or changing the GC column e.g. for a longer column (1.0 or 1.2m instead of 0.6m).
However, looking at the screenshot you included, it seems to me your separation between N2 and CO is ok. This assumes the TCD peak at 101s is N2 and the TCD peak at 165s is CO. I suspect the small hump in between (also visible on the m/z 28 trace) is either NO or HCN.
Before suggesting any changes, here is a question for you. Do you run your TC/EA reactor g-c tube filled with glassy carbon (g-c) chips only or with a mixture of g-c chips and Cr granules? If the former, have a look at the papers published by Matthias Gehre’s group on how Cr granules avoid side-reactions during thermolysis of N-rich compounds (also see Libby Stern’s paper).
Gehre, M., Renpenning, J., Gilevska, T., Qi, H.P., Coplen, T.B., Meijer, H.A.J., Brand, W.A. and Schimmelmann, A. (2015) On-line hydrogen-isotope measurements of organic samples using elemental chromium: an extension for high temperature elemental-analyzer techniques. Analytical Chemistry, 87, 5198–5205
Nair, S., Geilmann, H., Coplen, T.B., Qi, H.P., Gehre, M., Schimmelmann, A. and Brand, W.A. (2015) Isotopic disproportionation during hydrogen isotopic analysis of nitrogen-bearing organic compounds. Rapid Communications in Mass Spectrometry, 29, 878–884.
Hunsinger, G.B., Tipple, C.A. and Stern, L.A. (2013) Gaseous byproducts from high-temperature thermal conversion elemental analysis of nitrogen- and sulfur-bearing compounds with considerations for 2H and 18O analyses. Rapid Communications in Mass Spectrometry, 27, 1649–1659
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I come to you with an issue I'm sure has been addressed here before. I'm running d18O on protein samples (i.e. N-rich) and have virtually no separation (<15s) between N2 and CO peaks.
We're using a Thermo Delta V with Conflo IV Isolink EA. Reactor temperature is 1450C, carrier is 100 ml/min, sample dilution is 50%, and the column is run at 70C. Should I be looking at upping my dilution?
Judging by data I've seen elsewhere, it seems that greater separation is possible! Anyways, I'm all ears if anyone has tips on this. Thanks!!!
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