What would you look for and how?
Page 1 of 2 12 LastLast
Results 1 to 10 of 15
Like Tree4Likes

Thread: What would you look for and how?

  1. #1
    Full Member
    Join Date
    Nov 2011
    Location
    Oregon
    Posts
    100

    Default What would you look for and how?

    So if I could sweet-talk GC-MS and LC-MS-MS techs at work into testing my e-liquids, unofficially, does anyone have suggestions for which columns and conditions to use? Also, which would be the most interesting compounds to zoom in on (I don't care about PG, VG or nicotine since I already know they are there)?

  2. #2
    Forum Manager Verified Member
    ECF Veteran
    Supporting Member
    rolygate's Avatar
    Join Date
    Sep 2009
    Location
    Surrey, UK
    Posts
    7,727

    Default

    I guess contaminants:

    DEG - diethylene glycol
    diacetyl - butanedione
    pesticides - chlordane,
    http://www.who.int/heli/risks/toxics...aphyikishi.pdf
    Forum Manager - contact
    more vapers = less oppression

  3. #3
    Triple Guru Verified Member
    ECF Veteran
    Supporting Member
    tybin's Avatar
    Join Date
    Sep 2010
    Location
    WA
    Posts
    31,434
    Blog Entries
    1

    Default

    look for: petroleum solvent in high levels!
    Bethzilla likes this.

  4. #4
    Forum Manager Verified Member
    ECF Veteran
    Supporting Member
    rolygate's Avatar
    Join Date
    Sep 2009
    Location
    Surrey, UK
    Posts
    7,727

    Default

    Yeah.

    Hexane
    Benzene
    Bethzilla likes this.
    Forum Manager - contact
    more vapers = less oppression

  5. #5
    Full Member
    Join Date
    Nov 2011
    Location
    Oregon
    Posts
    100

    Default

    That all sounds like GC-MS, thankfully Getting LC-MS-MS is much harder. If I can blow the rust off my memory circuits, I might even be able to run the tests myself

  6. #6
    Quantum Vapyre ECF Veteran
    Supporting Member
    Kurt's Avatar
    Join Date
    Sep 2009
    Location
    Philadelphia
    Posts
    3,176

    Default

    Both of these instruments need to be high-res enough to have a databank of compounds that the peaks can be matched with. I do not know the column oven protocols, but the compounds being analyzed for are not ultra-high masses or BPs, so I would start with a standard oven ramping protocol and carrier flow, and see what you get. The time consuming part of these is to find what works best, and that can sometimes be trial and error, depending on the machine. Low-res MS will not identify well, but should give accurate nic levels, if you find the 162 peak.
    Deciding not to smoke is one thing. Forgetting to smoke is a different animal altogether.

  7. #7
    Nicotiana Alchemia Verified Member
    ECF Veteran
    Supporting Member
    DVap's Avatar
    Join Date
    Aug 2009
    Location
    On the road
    Posts
    1,518
    Blog Entries
    34

    Default

    I'd start with a 5% diphenyl dimethyl polysiloxane phase. A real workhorse. Maybe 0.32mm I.D. x 30M length and run the helium around 1.5 cc/min constant flow. Just a steady ramp from the appropriate solvent focusing temperature up to around 330C over an hour.

    Kurt, I think I have to disagree about the ability of low -vs- high res to make good identifications. Running in full-scan mode, a low-res can identify quite well assuming a non-coeluted peak. With coelutions, even a high res instrument won't be able to sort out the mix of masses from the coeluting compounds and the library fits will be poor. So the real limiting factor would be the complexity of the mixture... thus the ability of the column to resolve the close eluters.

    You want your library spectra to be run at a resolution similar to the resolution that you're using.

    Generally, you'll find the higher resolution instruments running in a selected ion monitoring mode where only a small subset of masses are being scanned thus increasing the mass dwell time and sensitivity, and using the filtering capability of higher resolution to distinguish masses of interest from very close masses coming from coeluting non-interest compounds.

    The mass filtering capability of a high res instrument comes into play when doing such a SIM analysis since at 1000 resolution (low res), mass 162.26 can be distinguished from a mass about 0.16 amu different (162.26/1000), thus if you're trying to look at mass 162.26, you'll be seeing a mass range of 162.10 - 162.42, thus non-interest coeluters can interfere if the mass is close enough to mass 162.26. Raise the resolution to 10,000 (high res), and discrimination increases to 0.016 amu (162.26/10000), thus lowering the indistinguishable mass range to 162.244 - 162.276. Much higher resolutions can be used, but with higher resolution, there is a sacrifice in sensitivity due to the physical focusing of the ion beam.
    Last edited by DVap; 11-24-2011 at 02:06 AM.



  8. #8
    Quantum Vapyre ECF Veteran
    Supporting Member
    Kurt's Avatar
    Join Date
    Sep 2009
    Location
    Philadelphia
    Posts
    3,176

    Default

    Thank you, DVap. Excellent information! You are clearly more up on GC-MS details than I am. Its been about 7 years since I ran spectra for my organic classes on our Agilent GC-MS, and because it was for particular reaction mixtures and solvents, it was about as plug and play as you could get. During the later part of my grad work and then postdoc, I was asking one of the local organic chemists if they had GC-MS, and could they ID compounds. The response was no, because it was low-res, and it was LC-MS not GC-MS, so I took that to mean you needed high-res. Clearly I wasn't getting the whole story. Glad you are bringing more hands-on knowledge here.
    Deciding not to smoke is one thing. Forgetting to smoke is a different animal altogether.

  9. #9
    PV Master ECF Veteran
    Join Date
    Mar 2009
    Location
    london uk / beijing china
    Posts
    5,001
    Blog Entries
    23

    Default

    Have a look also for Tin (and if there;s something there but perhaps not tin, what is it?).

    It's a great chance to get such data. Do kee and post the original plots. Ans thanks for doing this.

    +++

    Oh, i see you will test the liquids not the vapor. In that case there won't be any tin. What might turn up post-vaping would be more of interest, but of course not so easy to arrange.
    Last edited by kinabaloo; 11-25-2011 at 07:27 AM.

  10. #10
    Super Member
    Join Date
    Sep 2011
    Location
    Southern California (San Bernardino County)
    Posts
    361

    Default

    Reading kinabaloo's comment made me think that there may be an opportunity to test a given atomizers affect upon vapor produced by looking at a post-atomization condensate for the presence of additional elements and compounds.

    Since Chem is not my field, take this mention with a grain of salt.

    That said, I am happy to see the range of expertise participating in the vaping community.
    kinabaloo likes this.

Page 1 of 2 12 LastLast

Bookmarks