Beta

Slashdot: News for Nerds

×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Oil Detection Methods Miss Important Class of Chemicals

Soulskill posted about a year and a half ago | from the beverly-hillbillies-reboot-already-in-production dept.

Earth 46

MTorrice writes "For decades, scientists studying oil spills have relied on the same analytical methods when tracking the movement of oil and assessing a spill's environmental impact. But these techniques miss an entire class of compounds that could account for about half of the total oil in some samples, according to research presented last week at the Gulf of Mexico Oil Spill & Ecosystem Science Conference, in New Orleans. These chemicals could explain the fate of some of the oil released in the 2010 Deepwater Horizon accident and other spills, the researchers say."

cancel ×

46 comments

first post detection methods miss important class (-1)

Anonymous Coward | about a year and a half ago | (#42742713)

of FROSTY PISS !

Re:first post detection methods miss important cla (0)

Anonymous Coward | about a year and a half ago | (#42745179)

Can anybody tell me the first time "frosty piss" was used? I'm pretty sure I was the one that came up with it, but posting anonymously right now for fear of karma decay. I remember using it on a post as a laugh back in 1997-98 or so.... OK, cue the abusive trolls...

Re:first post detection methods miss important cla (1)

flyneye (84093) | about a year and a half ago | (#42746547)

You are correct, according to my records Anonymous Coward was first to receive a frosty piss ( with a twist of lime)

Re:first post detection methods miss important cla (0)

Anonymous Coward | about a year and a half ago | (#42747489)

You should see a doctor if your piss is < 50 F.

Gas chromatographs again... (4, Funny)

Antipater (2053064) | about a year and a half ago | (#42742823)

All right, according to the gas chromatograph, the missing oil compound is... love!? Who's been screwing with this thing?

Spoiler (2)

SuricouRaven (1897204) | about a year and a half ago | (#42742927)

The overlooked chemical class is oxidized compounds produced by the oil degrading after the leak, usually ignored because they are more difficult to measure than plain old hydrocarbons.

Re:Spoiler (3, Insightful)

mapsjanhere (1130359) | about a year and a half ago | (#42743285)

Not really, but with enough oxygen in it they start decomposing at the temperature of vaporization, producing short chain material that the automatic sample analysis suppresses. If you manually evaluate the samples you can still see it. Problem is that you get highly operator dependent results, and that makes comparing samples difficult. Also, once you've started to oxidize the material, biodegradation isn't far behind. So it's not really an environmental problem but literally an academic one.

Re:Spoiler (0)

Anonymous Coward | about a year and a half ago | (#42744327)

Can you explain this further? The authors of the paper explicitly state that the class of compounds are oxidized hydrocarbons which are formed by a combination of biodegradation and photooxidation. Seems to match exactly what SuricouRaven said.

Re:Spoiler (2)

mapsjanhere (1130359) | about a year and a half ago | (#42744557)

Sure it's an exciting science problem to look at - what individual compounds are part of the degradation chain of oil in the environment, how do we analyze it, what's the distribution, and is any of it toxic to wildlife. Plenty a PhD thesis in there. But the journalistic description of "we're missing part of a spill", implying that we're underestimating a problem, isn't really there IMO. Standard analysis gives you the amount of unchanged oil still around, stuff that kills birds by gumming up feathers etc. The oxidized material is quickly going to become water soluble or at least miscible as surfactant, and while not pretty it's going to dilute away in short order.

Re:Spoiler (1)

AK Marc (707885) | about a year and a half ago | (#42746389)

So would releasing tons of O2 under/in the affected area, bubbling up O2 and diffusing in the water cause more rapid decay of the oil? Would that make it easier or harder to clean up?

Re:Spoiler (2)

sFurbo (1361249) | about a year and a half ago | (#42748793)

So would releasing tons of O2 under/in the affected area, bubbling up O2 and diffusing in the water cause more rapid decay of the oil?

Yes

Would that make it easier or harder to clean up?

Yes

Or, to be less snarky, oxygen is important in degrading oil, and oxygen depletion makes the oil degrade much slower. And we don't really know how toxic these compounds are. They are more hydrophilic than hydrocarbons, so they are more rapidly taken up and more rapidly excreted by organisms.

Re:Spoiler (1)

AK Marc (707885) | about a year and a half ago | (#42753885)

Or, to be less snarky, oxygen is important in degrading oil, and oxygen depletion makes the oil degrade much slower. And we don't really know how toxic these compounds are. They are more hydrophilic than hydrocarbons, so they are more rapidly taken up and more rapidly excreted by organisms.

So we don't know if oxygenating would help clean it up or make it worse until we figure out where the "missing" oil went.

Re:Spoiler (2)

sFurbo (1361249) | about a year and a half ago | (#42758779)

Worse, even when we figure out where it goes, we don't know how toxic those compounds are. But even that is getting ahead of ourselves, we don't even know how toxic the compounds in oil are. We know how toxic PAH's are, because they are the major component of soot. In oil, however, the amount of alkylated PAH is much higher, and we don't know how toxic they are. Today, we measure the total petroleum hydrocarbon and a few of the PAH's to estimate the severity of pollution, which is fine if you have spilled paraffin and soot, but is probably not a very good probe for the toxicity of crude oil.

Re:Spoiler (2)

AK Marc (707885) | about a year and a half ago | (#42758941)

I'll just pretend it's not that bad and the government will take care of us. The alternative is too depressing.

Re:Spoiler (1)

sFurbo (1361249) | about a year and a half ago | (#42758963)

If it makes you feel better, I am working in a group that is trying to asses the toxicity of alkylated PAHs and their degradation products. Whether that should be comforting because we are doing something, or because I probably see the problem as larger than it is is left as an exercise to the reader ;-)

Re:Spoiler (1)

flyneye (84093) | about a year and a half ago | (#42746561)

If you use a dowsing rod, you aren't likely to miss anything...

Oxidized stuff (3, Interesting)

vlm (69642) | about a year and a half ago | (#42742949)

Oxidized stuff is kind of vague, chemically speaking. I'd love to look at the real paper (as opposed to the journalist interpretation) but I can't gain access. Just spins. Donno if its a free paper or paywall time.

Organic compounds containing oxygen... well, its been 20 years but are they talking about organic acids or ketones or aldehydes or alcohols or some freaky epoxides (that would be a WTF for sure). Doesn't have to be exclusive could be any mix of course.

I'm not a petroleum engineer but I play one on /. After cooking a million years underground I would think any trapped O2 would turn into water and CO2 as opposed to halfway stuff, so this indicates bioavailability after it leaked out... in other words its already half eaten up.

Re:Oxidized stuff (0)

Anonymous Coward | about a year and a half ago | (#42743039)

Re:Oxidized stuff (1)

kelemvor4 (1980226) | about a year and a half ago | (#42743167)

Your current credentials do not allow retrieval of the full text.

Re:Oxidized stuff (1)

Anonymous Coward | about a year and a half ago | (#42744135)

Oil spill research has generally focused on saturated and aromatic compounds and overlooked oxyhydrocarbons. This study shows that oxyhydrocarbons can be a significant mass of weathered oil, and this pool of carbon should be included into mass balance considerations after oil spills. Oxyhydrocarbons are relatively persistent, potentially making them recalcitrant tracers that could be used to assess degrees and kinetics of weathering, or for oil spill forensics, especially at weathering stages when other traditionally used oil compounds are degraded.

Re:Oxidized stuff (1)

MTorrice (2611475) | about a year and a half ago | (#42743073)

They haven't identified specific compounds yet--sounds like that is next on their to-do list. The scientists definitely think the compounds arise after the oil spills out of the well and sits out in the sun for a bit. Basically you're right: They're talking about the end results of oil degradation. But the big question is what do these chemicals do to marine life. Are they toxic? Or do they just sit around and living things ignore them.

Re:Oxidized stuff (0)

Anonymous Coward | about a year and a half ago | (#42743583)

But the big question is what do these chemicals do to marine life. Are they toxic? Or do they just sit around and living things ignore them.

The "fate of some of the oil" is obvious if you're not predisposed to reject the correct answer. In the Gulf, and many other places on Earth, natural hydrocarbons are abundant. They are also very energy rich. It would be profoundly astonishing if organisms in that habitat hadn't evolved to consume it.

The "missing" oil got eaten. Ecological disaster averted. Inventing a plausible yet incorrect answer that precludes having to acknowledge that truth is producing a lot of "science."

Re:Oxidized stuff (3, Insightful)

icebike (68054) | about a year and a half ago | (#42743705)

They imply that some of these can kill fish embryos in closed bays and estuaries.

one study linked unidentified oil chemicals to a spike in fish embryo deaths in San Francisco Bay

Really? How do they know it wasn't just raw sewage, or industrial chemicals if they didn't even identify the chemical, or even prove it came from the oil spill?

However, it appears their real complaint is this:

Reddy says overlooking these chemicals could hinder spill research in several ways, including thwarting scientists’ attempts to account for what happens to oil after a spill. After the Deepwater Horizon spill, government and academic groups could only explain the fate of about 75% of the oil released into the Gulf of Mexico. The oxidized compounds could be a portion of this “missing” oil, Reddy says.

Its not that the oil is "missed", its just that the oil once degraded to the point that it is not oil anymore is hard for them to measure with current methods, so they can't figure out where it went.

The main point, is that the oil is gone, degraded, oxidized, etc. The most dangerous (to marine life) part of the spill is gone.
The extent to which it is gone serves as an indirect measure of what these guys are trying to measure.

They offer very little in the way of support for their assertion that these chemicals are harmful.

Re:Oxidized stuff (1)

MTorrice (2611475) | about a year and a half ago | (#42743867)

Really? How do they know it wasn't just raw sewage, or industrial chemicals if they didn't even identify the chemical, or even prove it came from the oil spill?

The PNAS paper that looked at the SF Bay spill ruled out sewage and other chemicals found in the Bay. They suggest sunlight transformed crude compounds into toxic ones. The PNAS paper is in front of a paywall, I believe: http://www.pnas.org/content/109/2/E51.full [pnas.org]

Its not that the oil is "missed", its just that the oil once degraded to the point that it is not oil anymore is hard for them to measure with current methods, so they can't figure out where it went.

The main point, is that the oil is gone, degraded, oxidized, etc. The most dangerous (to marine life) part of the spill is gone.

But where degraded oil goes is a question scientists want to know, mainly because they don't fully understand what those compounds do to wild life. So even if the chemicals aren't the ones that originally spilled into the ocean, what they become is still of interest to researchers, because they know less about them.

Re:Oxidized stuff (2)

NatasRevol (731260) | about a year and a half ago | (#42744079)

" The most dangerous (to marine life) part of the spill is gone."

That's an unknown statement, and what the scientists are trying to figure out.

Re:Oxidized stuff (1)

fadethepolice (689344) | about a year and a half ago | (#42743087)

I work at a company that cleans oil spills and water. Sent this to a PHD project manager. His reply was "Interesting". So there is probably something to this method. Since the measurement of the amount not specified by the Gas Chromatography was dissolved en masse out of the sand there is some likelihood that some non-oil contamination was also dissolved out, and some likelihood that some was missed. Whatever the difference or perhaps deviation that is detected in the future form the results of this experiment, a 50% difference is just too large for it not to be a significant finding.

Re:Oxidized stuff (1)

icebike (68054) | about a year and a half ago | (#42743729)

50% "missed" simply explains where the oil went, after it ceased being "oil".

Re:Oxidized stuff (1)

Anonymous Coward | about a year and a half ago | (#42744035)

I can't stand this sort of myopic thinking. Human excrement is "gone" after you flush the toilet, but it still has potential effects depending on where it goes. Effects that are meaningful; the same type of effects that one would would worry about if we didn't have toilets. Dislike that ammoniac outhouse smell? Well it's certainly not the smell of urine or feces, so quit complaining!

It's still very meaningful to describe the hazardous oily residue which contaminates beaches and other habitats after an oil spill as "oil." That's because it looks like oil and harms like oil. The fact that it's not chemically identical to the crude oil which came from the well is the sort of semantic bullshit that an industry cheerleader would rely on to distract the public from legitimate concerns about environmental harm.

Re:Oxidized stuff (0)

Anonymous Coward | about a year and a half ago | (#42744193)

there is some likelihood that some non-oil contamination was also dissolved out

They considered that and wrote

These oxygenated hydrocarbon residues were devoid of natural radiocarbon, confirming a fossil source and excluding contributions from recent photosynthate.

Re:Oxidized stuff (1)

Anonymous Coward | about a year and a half ago | (#42743803)

http://www.scribd.com/doc/123045313/Oil-Weathering-after-the-Deepwater-Horizon-Disaster-Led-to-the-Formation-of-Oxygenated-Residues

To answer your question, yes -- organic acids, ketones/aldehydes, and alcohols were identified in the weathered oil samples.

Basically, they sampled oil from various locations (surface slick, rocks, sand) for 18 months. Using radiocarbon dating of representative samples, they verified that the samples originated from petroleum (not recently synthesized). They also verified that the samples came from the Macondo prospect by checking certain compositional ratios; the few that did not were excluded from the study. They used GC-FID, TLC-FID, elemental analysis, and a two-dimensional GC-GC method to analyze the samples. They used some internal standardization methods to verify that the oxygenated hydrocarbons were formed from the original crude oil -- this wasn't a case of the hydrocarbons washing away and leaving behind only oxygenated compounds.

The authors conclude that biological (bacterial metabolism?) and photochemical (sunlight-induced) mechanisms convert a significant fraction of crude oil into recalcitrant oxygenated hydrocarbons. The oxygenated hydrocarbons come off the GC later because they stick to the column; this means that many routine assays miss the oxygenated hydrocarbons. In other words, previous data overestimate the rate at which crude oil disperses in the environment. This could be by design -- it depends on your point of view at which point a product from the environmental degradation of oil can still be meaningfully called "oil." The authors push back against this point because of the potential toxicity and environmental longevity of these compounds:

"Oxyhydrocarbons also have the potential to exhibit toxic effects. [...] Toxicity is often assumed to decrease during oil weathering. This is because bioavailability,which is a prerequisite for compounds to manifest toxic effect, usually negatively correlates with hydrophobicity, and because less hydrophobic saturated and aromatic compounds disappear during oil weathering. However, oxygenation of oil residues during natural weathering has been suggested to increase their hydrophobicity, potentially making these residues more bioavailable."

Re:Oxidized stuff (1)

sFurbo (1361249) | about a year and a half ago | (#42748801)

From the abstract of the actual article:

The incorporation of oxygen into the oil’s hydrocarbons, which we refer to as oxyhydrocarbons, was confirmed from the detection of hydroxyl and carbonyl functional groups and the identification of long chain (C 10 - C32 ) carboxylic acids as well as alcohols. On the basis of the diagnostic ratios of alkanes and polycyclic aromatic hydrocarbons, and the context within which these samples were collected, we hypothesize that biodegradation and photooxidation share responsibility for the accumulation of oxygen in the oil residues.

Of concern (1)

Frontier Owner (2616587) | about a year and a half ago | (#42743259)

when they extracted the organic compounds from the sand, did they normalize this against untainted sand from the area? Sand is going to contain some organic compounds naturally from the various marine life. Does their tests differentiate between crude oil compounds and rotting whale blubber compounds or seagull droppings?

Re:Of concern (0)

Anonymous Coward | about a year and a half ago | (#42743723)

All good questions. Doubtless they will be answered. Probably several years after the "OMG BP KILLED THE SOIL" headlines are perpetrat^H published. Then we'll learn that decaying hydrocarbons and decaying feces are ecologically indistinguishable.

Don't look for it here, though. Results like that are considered trolling around Slashdot.

Re:Of concern (0)

Anonymous Coward | about a year and a half ago | (#42743979)

Of course folks like you would never dream of educating themselves, so you will probably be extremely surprised to know that environmental toxicologists have already been working on characterizing the toxicological profile of decaying oil. It's not looking so good. Here are the references that this paper alone cites:

Jones, D.; Scarlett, A. G.; West, C. E.; Rowland, S. J.Toxicity of individual naphthenic acids to Vibrio fischeri Environ. Sci. Technol. 2011, 45 ( 22) 9776– 9782

Vrabie, C. M.; Sinnige, T. L.; Murk, A. J.; Jonker, M. T. O.Effect-directed assessment of the bioaccumulation potential and chemical nature of Ah receptor agonists in crude and refined oils Environ. Sci. Technol. 2012, 46 ( 3) 1572– 1580

Lübcke-von Varel, U.; Machala, M.; Ciganek, M.; Neca, J.; Pencikova, K.; Palkova, L.; Vondracek, J.; Löffler, I.; Streck, G.; Reifferscheid, G.; Flückiger-Isler, S.; Weiss, J. M.; Lamoree, M.; Brack, W.Polar compounds dominate in vitro effects of sediment extracts Environ. Sci. Technol. 2011, 45 ( 6) 2384– 2390

Incardona, J. P.; Vines, C. A.; Anulacion, B. F.; Baldwin, D. H.; Day, H. L.; French, B. L.; Labenia, J. S.; Linbo, T. L.; Myers, M. S.; Olson, O. P.; Sloan, C. A.; Sol, S.; Griffin, F. J.; Menard, K.; Morgan, S. G.; West, J. E.; Collier, T. K.; Ylitalo, G. M.; Cherr, G. N.; Scholz, N. L.Unexpectedly high mortality in Pacific herring embryos exposed to the 2007 Cosco Busan oil spill in San Francisco Bay Proc. Natl. Acad. Sci. U.S.A. 2012, 109 ( 2) E51– E58

Incardona, J. P.; Vines, C. A.; Linbo, T. L.; Myers, M. S.; Sloan, C. A.; Anulacion, B. F.; Boyd, D.; Collier, T. K.; Morgan, S.; Cherr, G. N.; Scholz, N. L.Potent phototoxicity of marine bunker oil to translucent herring embryos after prolonged weathering PLoS One 2012, 7 ( 2) e30116

Re:Of concern (0)

Anonymous Coward | about a year and a half ago | (#42745475)

The fact that decaying oil is 'toxic' is orthogonal to my point. Decaying sea gull feces are 'toxic' as well.

In any case, whatever toxicity one finds is probably not a concern... for the ecology. With no help from man at all Earth dumps the estimated equivalent [nap.edu] of over 3x the contents of an Ultra Large Crude Carrier into the worlds oceans every year, with the Gulf alone accounting for about a third of that. If life were unable to cope with the toxicity of decaying oil the Earth would be lifeless.

You see, not only can I read academic material, I can do math. The math tells me fear mongers like you, and the hysteria you've been trained to indulge, are full of shit.

Re:Of concern (0)

Anonymous Coward | about a year and a half ago | (#42751347)

Wow, you must be some ecologist. Life continuing to exist isn't the concern here. It's regional catastrophes and extinction events that most people worry about, not the total extinction of life on earth.

Additionally, your math skills are seriously weak if you didn't notice that the Deepwater Horizon blowout released 3x the usual annual seepage (4.9 million barrels = 613 kton) for the gulf area. You know how life copes with UV light despite its toxicity? That doesn't mean that we can simply triple or sextuple exposure for some period of time and handwave away the negative effects because "life can cope with the toxicity." If you seriously think that's how it works, then you're a moron.

Re:Of concern (0)

Anonymous Coward | about a year and a half ago | (#42743877)

Yes, they used radiocarbon dating on the samples to verify the carbon in their samples came from petroleum. Additionally, they ran other common tests to verify which oil deposit was the source of their samples -- they threw out the samples which were not shown to originate from Macondo.

Are you familiar at all with the concept of peer review?

Re:Of concern (1)

reverseengineer (580922) | about a year and a half ago | (#42744317)

They established the origin of the hydrocarbons by measuring the carbon-14/carbon-12 ratio. Organic compounds made by living things on the surface of the earth will have a small amount of carbon-14 incorporated. Just about all the carbon-14 that had been present in the oil will have decayed with no opportunity for replacement, Their results for their oil-soaked sand show ratios of a few tenths of a percent of the atmospheric value, making it it likely that the vast majority of the hydrocarbons present were from sources which had been dead for eons.

Also, they have profiles of the same oil taken at the source well, surface slicks, and contaminated sand. While the oil degrades with environmental exposure, there is clear similarity among the compositions of the samples. The supporting information [acs.org] gives a lot of details on the experimental methods.

Re:Of concern (1)

PPH (736903) | about a year and a half ago | (#42745329)

OK, but some of the carbon in the soil in my back yard has been dead for eons. So its not atmospheric ratios they have to look at, its a control sample from the ground (beach, whatever).

Re:Of concern (1)

sFurbo (1361249) | about a year and a half ago | (#42748827)

The half-life of C-14 is 5730 years, and unless you have upwelling of very old deep sea water or an oil spill, organic matter exposed to the sun is not that old. Still, a clean beach sample would have been a nice blank sample to compare with.

Re:Of concern (1)

PPH (736903) | about a year and a half ago | (#42752031)

organic matter exposed to the sun is not that old.

What does sunlight have to do with it? Carbon that has been buried in the soil decays from C14 to C12. There is no reaction path to convert it back to C14. C14 is produced in the upper atmosphere by a reaction between Nitrogen and cosmic rays at a known rate. Once atmospheric C14 is bound into living (or dead) material, there's no going back to C14.

So some of the carbon in the soil in my back yard may have been there since the last ice age (or before). Until it was exposed by erosion or a backhoe. Unless something alive eats it and aspirates it as CO2, it could be very old.

Re:Of concern (1)

sFurbo (1361249) | about a year and a half ago | (#42758759)

What does sunlight have to do with it?

Well, the atmosphere will do, I guess. Or, to be more specific, oxygen. My point was that, barring some very special circumstances, all organic C is in equilibrium with the atmosphere on at least a decade or century timescale. Unless your backyard was a bog or otherwise under water until very recently, I doubt very much of the carbon is old. If there is oxygen present, life will make carbon into CO2, and there is oxygen present in most soil, at least in some parts of the year.

Incompetence (0)

Anonymous Coward | about a year and a half ago | (#42743983)

How can the oil industry not understand basic chemistry?
They should know; with all of their time, knowledge, money and experience.
Something is very wrong. Willfully wrong? Ignorance?
Shame on the nincompoops!

limitations of GC (0)

Anonymous Coward | about a year and a half ago | (#42747867)

Based upon the article, most of the people who get paid to do these oil
spill studies appear to acknowledge very little in their studies about
the limitations of gas chromatography (GC) in relation to the wide
variety of compounds that are present in whole crude oil, to say nothing
of their degradation products. This is irrespective of whether or not
the compounds present in the samples they received from the oil spill
site were naturally present in the original crude oil or are oxidation
products, reduction products, or just simply changed by microbial
activity.

A GC analysis only detects compounds that are volatile. Nominally this
is estimated to be about 5% of all known compounds. Fortunately for us,
GC-able compounds in whole crude oil comprise about 1/3 to 2/3 of all of
the molecules in the oil. The Gulf of Mexico oils have about 50% or more
volatile constituents, thus the author of the article is in the correct
ballpark. It is pretty hard to get asphalt through a GC column.
Techniques other than GC are appropriate for analysis of "the rest" of
the sample.

Even high temperature GC, not a technique used by most oil spill
chemists, tops out at about 450 degrees C. As a rough measure of the
amount of GC-able material in a whole crude oil, distill the whole
crude oil and record the volumetric percentage that has been collected
when the distillation temperature reaches 450 C. The difference is the
non-GC-able portion that remains in the pot. It is significant.

For detailed insight into the composition of the non-GC-able portions of
whole crude oil you may want to read some of the petroleum papers from
the Alan Marshall group at the National High Magnetic Field Laboratory
in Florida (www.magnet.fsu.edu). In particular, read petroleum
related papers by Alan Marshall, Ryan Rodgers, Amy McKenna, John
Schabron, and their co-authors.

Re:limitations of GC (1)

sFurbo (1361249) | about a year and a half ago | (#42748863)

Your points are generally correct, but your test for the non-GC-able prtion is not accurate. Compounds with boiling points well above the temperature of the column can be eluted from GC by having a high enough phase ratio, or a high enough flow, or waiting for a long enough time. A boiling point of 450 degrees C is reached at around C-30 [elmhurst.edu] , and I have seen presentations of GC of alkanes up to C-60, in I think I have heard about GC of up to C-100. In that range, it becomes more a question of thermal stability, but anything present in oil will have experienced prolonged periods of elevated temperature, so nothing particularly thermally labile should be left. However, this does not go for the degradation products.

Re:limitations of GC (0)

Anonymous Coward | about a year and a half ago | (#42757633)

You are correct. I was giving a very general example for an audience
whose professional career does not involve gas chromatography and
petroleum crude oil. Due apologies. Thus, the concept of non-GC-able
compounds has too much of an absolute implication for anything other
than a general discussion and is not technically correct in all cases,
such as the ones you cite. Volatile organic compounds that do not
decompose at the GC oven elution temperature are generally easy to GC if
their boiling points are less than the maximum GC column temperature,
which is typically less than the maximum GC oven temperature, and become
increasingly difficult to GC at higher boiling point temperatures. At
some point it becomes futile and other analytical methods become more
appropriate.

I have whole oil high temperature GC's of paraffinic crude oils run on
aluminum clad high temperature GC columns showing n-alkanes well over
n-C100. However, doing quantitative GC work on crude oils above the
n-C30 to n-C45 range and higher is not something that I have seen
typically done by those doing oil spill contract GC work. The authors
of the C&E paper are basically correct. Their finding is just not
surprising to me.

In the higher n-alkane range we still don't know if what we are seeing
in the GC chromatogram are the free n-alkanes from the crude oil, the
n-alkane alkyl side chains that were thermally clipped away from the
asphaltene ring systems in the GC injection port and/or column, or a
combination. The answer may vary from crude oil to crude oil. For those
of us who work in these areas there are a huge number of things yet to
be definitively established - which is why we have labs full of people,
instruments, and projects anchored back to ideas. Your input is
certainly welcome.

Please correct me if I am mistaken.

Check for New Comments
Slashdot Account

Need an Account?

Forgot your password?

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>
Create a Slashdot Account

Loading...