Talk:Gas chromatography-mass spectrometry
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This article has been improved by the Cleanup Taskforce to conform with a higher standard of quality. Please see its Cleanup Taskforce page for more details on this process, and possible ideas on how you can further improve this article! |
[edit] Cleanup and revision
I started to redo quite a bit of this article. I felt while some things were not necessarily incorrect, they seemed as if they could be misleading. Furthermore what I felt was important information was totally missing from this article.
Babbles 04:52, 24 July 2007 (UTC)
What does this need before it can be removed from cleanup? Please list here and' on the WP:LO page. Thanks! JesseW 23:54, 19 Oct 2004 (UTC)
--Mmcdougall 16:29, 13 May 2005 (UTC)
Main page is getting pretty close to "ready-to-go" I think. The redacted information (now at the bottom of the talk section), should not be lost. We should find a more appropriate home for it. Similarly, there is detail in that section that should be pushed to CG and MS sections. Sentor material should be editted and moved to Sentor.
I just read this article for the first time in a long time and I think it looks much better, but it still needs some work. Should probably add a section about pharmaceutical and/or bioanalytical methods. I personally feel the section about Full Scan vs SIM is a bit misleading if not somewhat incorrect. If it is worth anything I have been running GC & GC/MS instruments for ~8 years now and I'll try to put my two cents in but that entire time thing is restrictive at times.
Babbles 01:12, 24 July 2007 (UTC)
[edit] Other comments
"Law Enforcement
GC-MS is increasingly used for detection of illegal narcotic, and may eventually supplant drug-sniffing dogs."
Anybody have some solid information on this? While there are some quasi-portable GC's that can be taken into the field (they put one on the Mars rover), there are most certainly not hand portable units. Additionally there are certain factors like instrument maintenance, run times, and quality control which makes it unlikely that it would replace a drug sniffing dog. At least not in the near future.
Babbles 01:27, 24 July 2007 (UTC)
Okay, so I admit, it's a bit chatty. It's based on a paper I wrote for a scientic evidence class. It's really just talking about how GC/MS works and what its strengths and limitations are. So there's really nothing that's specific to Scientific Evidence, except towards the end when it starts talking about how it functions under certain legal tests, but that's still relevant.
--Jvraba 10:20, 21 Jul 2004 (UTC)
Okay, so I've started to seperate the legal discussions under seperate headings. The article used to have tons of footnotes, so if things seem like they pop out of nowhere, they might need to be fixed. Actually maybe someone has a better article to adapt for this purpose. But I think it's pretty useful.
--Jvraba 06:30, 23 Jul 2004 (UTC)
If you create a new section, try to use the equal-sign convention (two equals signs for a headline, three for a subhead, four for a sub-sub-head) so it's added to the table of contents rather than just bolding.
Salasks 14:13, 23 Jul 2004 (UTC)
This article has a lot of legal information I was unaware of, but it needs work by someone more familiar with GC/MS. In particulat, I think it poorly describes the technique. One problem with the paper is that it repeatedly refers to mass spectrography. Should be "spectrometry". Cool Hand Luke 23:24, 28 Sep 2004 (UTC)
I'll put a link to the original paper. This version takes out all the footnotes, obviously. Some things which may seem like poor or superficial descriptions may be the product of depending on a footnote that is no longer there. I have no problem with this thing being quite gutted. And maybe I should excerpt the paper to address the legal implications of GC/MS and leave the rest to real scientists. As far as spectrography / spectrometry, it seems to be used interchangibly in certain literature, although this may reflect an artificate of certain periods of development. I began the paper with huge footnotes on the history of GC and MS, so maybe this had a lasting effect on my style throughout.
--Jvraba 03:01, 17 Oct 2004 (UTC)
- Actually, I think I was too harsh on this article. I think it'll require a lot of work, but all of this legal information is actually a very good thing. Although it probably needs to be reorganized and made less verbose, I think most of this information is appropriate. I would imagine lots of folk in chemical sciences would find the article interesting just for the legal aspects of a familiar technique. Unfortunatly, I don't have very much time to work on it now. Cool Hand Luke (Communicate!) 08:29, 17 Oct 2004 (UTC)
- The article shows some promise - I have added links to the text but that in itself took me an hour. It needs de-essaying and things like "needle in a haystack" need to come out. I reckon it would make a really good article if you removed the half of the content that was making it too verbose. I will continue to edit it over the next few weeks, but it will take many revisions as it's too much to do in one go. It probably needs about 10 hours work in total. GregRobson 20:23, 30 Nov 2004 (UTC)
[edit] Proposed introduction
I'm willing to do the cleanup. It will take me quite an effort to eliminate all the wordy "deadwood" in this article. Could the original author provide references so that it will be easier for me to rephrase parts of the article? Allentchang 08:21, 23 Nov 2004 (UTC)
- That's great that you are willing to work on cleaning this up. I assume you've asked at the Talk page of the first contributor(see History)? JesseW 10:31, 23 Nov 2004 (UTC)
- I sent Mr. Chang the artciel. I believe he's working on it now. As a lawyer, I was a bit "cliff's notes" in my understanding of the underlying science, although I tried to do my best to go through all the seminal journal articles. Some things which sound like omissions in the text above are actually nuanced or more clearly explained in the footnotes. Anyway, it seemed like a good idea at the time. But if it doesn't work out, I'm all for completely gutting this entry and starting over again. --Jvraba 02 Dec 2004
- I'll get the cleanup done before Christmas. My background is in electrical engineering, but I've editted technical articles before. allentchang 21:56, 11 Dec 2004 (UTC)
[edit] Legal implications section
The latter third of this article about the implications of GC/MS and related technologies in the American legal system is very interesting. In fact I thought it must have been copied from somewhere else becaue it was very clearly written not as a Wikipedia article. However it seems the author has put it here so it's legit. However, I think it doesn't really fit on this page. I think there should be a page on scientific evidence in the legal system, and this section can serve as the foundation of that article. I'm not going to move it or anything, I just wanted to provide my thoughts and how best to organize this information. I don't think the legal stuff should stay on this page in the current level of detail, but we should keep it somewhere else and link to it. Nohat 00:53, 16 Dec 2004 (UTC)
Probably true. Well, before I pasted in my article there was no GC/MS article, and people kept asking me about GC/MS, so I figured it was better than nothing. I know there are certain problems with the article as it currently stands, because obviously, especially towards the end, its analytical framework is from the scientific evidence (legal) point of view. Was it originally written as a Wiki article? No. It was originally written as a term paper. But it seemed generalized enough to be useful. One of the problems it had, is that some of the more specific scentific quibbles remained in the footnotes which I did not paste in. Allentchang, who is currently working on the article, has the version complete with footnotes. I'm actually looking forward to seeing this reworked. --Jvraba 19:32, 18 Dec 2004 (UTC)
The university library where I'm checking several sources on the subject is closed for winter break so it will take me much longer than I had promised. Allentchang 20:24, 24 Dec 2004 (UTC)
[edit] Clarify this paragraph
"Alternatively, the single-magnet analyzer chamber will deflect the various particles through an electromagnetic field within a long curved tube. The lighter particles traverse the analyzer tube the fastest. The particles emerge from the magnetic region and strike the detector, transferring its charge. This activates the recorder which takes note of the atomic mass through the mass/charge ratio and evaluates concentration of that molecule contained in the sample."
Please clarify the above paragrapgh. So how exactly does the single-magnet analyzer discriminate between particles of different mass to charge ratios? I've read websites that suggest that single magnet is tunned to allow particles of a certain mass to charge ratio to be able to complete the journey through the long curved tube. Particles with a different mass to charge ratio has a trajectory that is incompatible with the pathway offered by the long curved tube and therefore these particles collide on the wall of the tube. Allentchang 20:59, 24 Dec 2004 (UTC)
[edit] I invite anyone to cleanup sections after MS components
I invite anyone to cleanup sections after MS components. There's already a complaint that this article is more than 32k. There are sections of the article after MS compennts that I cannot properly clean up without consulting the book by Giannelli, Paul C. and Imwinkelried, Edward J. The UC Berkeley library does not have that book for some reason. Allentchang 22:43, 7 Jan 2005 (UTC)
[edit] GC/MS analysis
I've looked at the section on GC/MS analysis and got very confused. You said that two kinds of analysis are possible: comparative and original. You then proceed to explain about the comparative analysis in the first paragraph. Then in the second paragraph you vaguely mention about "another analysis." Is this other analysis the "original analysis"? If not, then there is no where in your GC/MS section that talks about original analysis.
Additionally, you later mention "full spectrum" analysis and selective ion monitoring. It seems to me that you are talking at most five different types of analysis instead of two: "comparative," "original," "another," "full spectrum," and "selective ion monitoring." Allentchang 22:54, 7 Jan 2005 (UTC)
[edit] Ruthlessly Excised sections for clarity
Heres the original bits.
- See http://www.chemistrydaily.com/chemistry/Gas_chromatography-mass_spectrometry - the rest cut per WP:C --Kkmurray 02:18, 15 June 2007 (UTC)
[edit] GC/MS Analysis
Would anyone object to a section in the GC/MS page focusing on some practical observations from someone who works in a lab that does both environmental analysis and drug detection work? We tend to be very focused on supporting the identification with various kinds of quality control samples to show the system is working. We are also always up against the concept of "detection limit". Non-technical clients can't get over the idea that we can't say a sample does not contain a given compound. The best we can do is say we saw no reliable signal above the detection limit. The second question is always "How much is in there?", so quantitation should probably get a mention.
[edit] My suggestion?
I'd add a sentence like "GCMS has a very low detection limit, and can be used to determine how much of blah-de-blah is is present, unlike such-and-such. Then I'd put my insights re: quality controls ect in the detection limit article. Sadly, I'm not an expert on GCMS, so I can't make the "true" statements in good faith.
[edit] If you know about these machines, please help with a related article
See HHO gas. A scientist by the name of Ruggero Santilli wrote a journal paper claiming a new gas based on electrolysis of water with all kinds of "anomalous properties" like not obeying the normal gas laws and having a different amount of energy in different circumstances. Most of his evidence is in the form of spectrometry scans, like a scan showing a peak at 5 amu and one showing monoatomic oxygen that "can only be explained" by his pet fringe theory of physics, etc. Can someone familiar with these devices help me out? Look over the paper (in the References section) and the graphs and point out any:
- Glaring errors (there are several typos and incorrect units in the paper)
- Internal inconsistencies (why do the same scans of the same compound look so different from each other?)
- Obvious misinterpretations of the graphs (is there normally a peak for monoatomic oxygen because of the electrical dissociation in the spectrometer?)
- Areas that would have to be looked into further to determine the validity of these tests or other places these claims would likely be responded to
— Omegatron 15:04, 8 June 2007 (UTC)
[edit] new sections: split/splitless and purge and trap
Just added two new sections. Not sure if they should be independent sections or part of 'Instrumentation'. Anyway, I need to add references but most of the info is from training materials not available to the public (I am a GC-MS operator). I will be making articles about Purge and Trap GC-MS when I get chance. Also I think we should standardise the form we express GCMS. In this article the forms GC/MS and GC-MS are both in use.
Tangaloomaflyer 11:12, 10 October 2007 (UTC)
[edit] Technical Error on Page
This page, as it stands, should be entitled GC-scanning MS.
As this topic relates to both GC and MS, it is important to bear in mind that there is a page dedicated to Mass Spectrometry, where most Mass Spectrometers are described.
A scanning mass spectrometer looks at 1 ion at a time and throws away the rest. It then moves onto the next ion. If one looks at it critically, one will see that a SCAN is just a very long and sequential SIM.
A Time-of-Flight Mass Spectrometer does not "scan". It records complete "snapshots" or spectra, not throwing away any masses.
This has 2 implications: 1) A TOFMS cannot do SIM. 2) A TOFMS provides you with more accurate repesentations of the GC peaks.
By claiming that SIM is more sensitive than SCAN, one also assumes that one is looking at a smaller number of ions under SIM than under SCAN. This last claim is a very difficult one to make, especially if one considers TOFMS instruments as included under "SCAN".
A TOFMS can be just as sensitive as other Mass Spectrometers running under SIM. This has been shown over and over by TOFMS users. It really does depend on whether one does 1 ion SIM (nice to show off SIM, but useless in real life) or whether one does 3+ ions SIM (Retention Time + 3 ions seems to be the bare minimum for positively identifying chemicals). At 3 ion SIM level, a TOFMS is often just as sensitive.
12:53, 11 November 2007 (UTC)
- A triple collector IRMS doesn't scan. GraemeLeggett 10:38, 12 November 2007 (UTC)
