dormouse (Member)
04-19-00 08:50
No 122810
      Need help with GC -Osmium  Bookmark   

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Author  Topic:   Need help with GC 
Member   posted 11-05-1999 12:11 PM          
I will have access to some gas chromatographs soon. I want to test a few oils, can anybody with experience in this field tell me which heating rates, temps etc I have to use for the usual essential oils? Any differences when testing amines? What column types can be used for them?
Or do you have some refs lying at home with some numbers? Please post, my access to them will be limited.
Junior Member   posted 11-08-1999 01:02 PM          
Just use the normal settings (25-250C 5-15C/min)
Almost any 25m capillary column will give you a nice split.
Make sure that the sample is clean, tar in a column is a mess.
Hope you not will find to manny tops

Junior Member   posted 11-10-1999 11:23 AM          
Method 969.13: AOAC Official Methods of Analysis: dihydroanethole, dihydrosafrole methylsalicylate and safrole in nonalcoholic beverages; GC method.The method adds methanol to the sample followed by steam distillation and rinsing the condenser with more methanol. Add satd sod.chloride and extract with chloroform, then evaporate down to a small volume. GC / FID; 1.8m x 4mm id glass column packed with 15%[w/w]polypropyleneglycoladipate [Reoplex 400] on 60-80 mesh GasChrom P. Temps: column 130 C isothermal, detector 220 C, injector 180 C. Nitrogen carrier 40psi at ca. 90 mL/min. Column may be programmed over range 90 - 150 C at 2 C/min.
I agree with hest's post, but this might be an alternative for you.
Member   posted 11-10-1999 12:15 PM          
Thank you. Anybody who happens to stumble over another ref, please tell me!
Member   posted 11-29-1999 12:18 PM          
That thing I used during the last week seperates _everything_. I kept injecting the dirtiest shit and it always produced good separation. 30m capillary column helps a lot. And when the column is dirty, just heat it up to 350C for an hour and it works again.
Those fuckers even have a brand new GC/MS in that very room. It's standing there for almost 3 months now, complete with autosampler and all, and nobody has used it yet. NOBODY! Shit, I could have done the work in a fraction of the time, but nooo, they won't let me use that baby. You assholes, when it's still a virgin in another three months, I'll take it home!

Bright Star
Member   posted 12-01-1999 12:21 PM          

Analytical Chemists have the best toys.

Member   posted 12-01-1999 04:22 PM          
That GCMS thing is not located in the analytical department. They don't really need that, it's just there because they have to spend their budget. These fuckers have so much money, there are unused, almost new instruments everywhere. I've seen several IR spectrometers in working condition waiting there to be picked up. Only one is actually in use, the others slowly corrode and nobody cares. Too bad they don't fit into a backpack.
Bright Star
Member   posted 12-07-1999 01:29 PM          
If its any consolation ...
Same deal here. Except we have two 60MHz NMRs gathering dust. I weep every time I pass those things. Sittin' in the hall ... one actually has a pile of old text books on it (got one of those).

At least one analog IR. Several GC's. A two-ton mass-Spec .... old Beckman. Its sad ... I'd love to get those things and have all ya'll send me ~10mg.

Plus a handlers fee of course

Member   posted 12-08-1999 04:01 AM          
Hehe. Ok boys, you all send me a 1g sample of your honey and 250$ and I'll analyse it. IR, GC, NMR, molecular weight determination, microanalysis. Of course I only need about 100mg for analysis, the rest is for me
Junior Member   posted 12-08-1999 07:50 PM          
You guys might be kidding, but this idea may have great appeal to the furtherment of clandestine methodology. Instead of the second-guessing and crude analyzation techniques usually used by the underground researcher to determine product and intermediate identity, someone could have thier compounds analyzed to determine definate identity. Spectra could be posted to a website to allow for group discussion. Logistics and security would be an issue, and of course if the analyzations were run by an individual (as opposed to a group) time constraints would only allow for sample testing for those persons expereinced/compitant and with a novel technique.
Member   posted 12-08-1999 08:05 PM          
Os. and B.S.: Are you serious? At the U I'm at, all leftover equipment is sold the general public no less, right now our service is selling a a carbon analyzer, a couple fume hoods, autoclaves and spectrophotometers, all in working order (well, some of the spectrophotometers are down...)...they've even had GCs for sale in the past...usually for pretty remarkably low prices...
Danger...ethnic digestion tabernacles on now; privacy robotic doubles, rolling rehab threat machines, reformulators, heightened insensitivity vehicles, erotic invisible empires on now...

Member   posted 12-09-1999 05:45 PM          
Selling used equipment? You mean saving taxpayers' bucks?? Shit no, all we do here is wasting money. Every piece of equipment not used anymore is put in this huge storage room, where it stays for a few years until its usefulness is totally forgotten. Working equipment is rotting there. When it has aged there for a few years and certainly doesn't work anymore, it is simply dismantled and thrown out. Of course the different metals and plastics are separated, we are environmentally friendly! Oh yes, we have to make room for all that fancy new equipment nobody really needs. Just like the argon we use here. Nitrogen is much cheaper and would work for 99% of the reactions, but hey, of course we use argon! Sounds much better in the publications (Look dude, they use argon!).
Did I already mention we have about 6 heating mantles and 10 magnetic stirrers per person working in that joint? Of course only a small fraction of the people is actually doing lab work. Oh yes, a stirrer usually lasts 2 to 3 years, before it is replaced here. You know, cleaning it is way too much work. They are used until they are all dirty and nobody wants to touch it anymore, and off it goes to that famous storage room.
Oh yes, tech support for the GC/MS is in the house. They are working hard for three days already trying to make it finally work, adding even more autosamplers, detectors and electronics. Oh yes, we have to break that 200,000$ barrier, right? But when I don't see results in two months, that baby is mine!
K.C. Nicolaou
Member   posted 12-09-1999 11:02 PM          
Hey Osmium, if they really want to waste money, why don't you put a request in for a couple of prep HPLC's? Pretty pricey, but when you want that 2g of "oh my god I can't even count numbers as high as my TLC has spots" dirty shit separated into nice little pure fractions in an hour or two, they're very nice. We just got one of these things at my work a couple months ago, and it is possibly the fucking greatest thing ever invented by man. Even niftier is the fact that it is set up so that each fraction is shot onto a LC/MS for analytical purposes. Oh, and can you say "chiral support"? I sure can .
Bright Star
Member   posted 12-14-1999 11:02 AM          
This is exactly what has happened at my University. On the way in the building today, I passed:
The 2 60MHz NMR's
Two analog IR's (dating from the ~early 70's?)
Two UV-Vis (with flow cells)

and .. somthing New!

A Class 3 Continuum Hg Laser ... No idea what I'd do with it ... but wouldn't it be cool?

OS- Same thing here.
I have gotten most of my lab shit out of the dumpster. HotPlate/Stirrer that needed cleaning. Mantles that needed a quick solder job. Glass with a chip out of it. Variac's in need of new cables. Stands, stoppers (in need of plasticizer), PUMPS! ... the list goes on ... I can still hear the cleaning crew ...

"Well ... ther's tha white boy agin ... he kwazy gettin in tha dumsta like tha...'

We have dedecated MS labs with MALDI, Chemical ionization, electro-spray, and Time of Flight equipment. We have dedicated NMR labs with 2x200MHz, 2x300MHz, a 600MHz and an 800MHz.

The problem really is ...nerds are pack-rats. I am. The NMR guy is to. The MS guy has different toupe's for every day of the week. So .. even if they have much better shit, they can't get rid of the stuff that they are attached to.

K.C. - Is it one of the counter-current models? Centrifugal?

Teo - They don't sell anything that works. and ... there are places that you can send your shit too .. and they will tell you if its the real shit ... but if you can figure out a way to get a Melting Point out of it ... then thats just as good if you ask me ...

Junior Member   posted 12-27-1999 10:29 PM          
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