Chromatography machines help to separate a mixture of compounds by exploiting a few factors, but to keep it simple, mainly interactions between the solid phase and the mobile phase. The two main types are GC and LC (Gas and liquid as your carrier). GC is reserved usually for specific types of compounds, mainly volatile compounds that will readily enter the gaseous phase without decomposing. In GC the carrier is an inert gas, in LC it's a solvent or mixtures of solvents. Generally LC today is talking about reverse phase where you use more polar solvents and a C18 (derivitized silca beads) non-polar stationary phase.
I can tell you that I've run a few samples from synthesis projects in a GC-MS solely because we had no LCMS at the time and it's just frustrating. Everything decomposes and fragments and you're left trying to piece together a puzzle of what your original products may have been. In an LC there wouldn't be a problem.
In chemistry you select the most appropriate techniques or pieces of equipment that fit your particular need at the time. While an old GC probably has a lot less moving parts than a newer one, it still comes down to whether or not it is the appropriate machine for what you want to do. At first glance, yes I would say GC is cheaper than LC, as your carrier gas is a lot cheaper generally than bottles of ACS grade solvent. But who cares if it is cheaper if its useless for your applications?
Honestly I love TLC because it's really cheap and fast. You could even start with TLC of crude mixtures, it's what tons of chemists still use every single day because it offers decent resolution very quickly and affordably. You need a TLC plate (you can make your own even) a solvent, a jar, a spotter tube, your mixture, and then generally a UV llight or a stain if your compounds aren't pigmented.
Yes an MS is strongly recommended because a mass to charge ratio out to X decimal places of certainty is really more trustworthy for a compounds fingerprint ID than a peak on a chromatogram because retention times can be easily influenced while its m/z will remain the same given consistent conditions.
An MS isn't a machine you really just plug and play though, it requires a lot of other consumables, upkeep, and setup. It's also a heck of a lot more expensive.
Even when I have reactions with 2 reagents that turn out 6 products, it's a pain in the ass trying to figure out exactly what they are. In 5 minutes with an LCMS I could tell you what every single one was. When I had one to use alongside synthesis, I was spoiled. I now have to run countless TLC plates, run silica columns, and then take NMR only to still be partially confused because of crazy HNMR spectra.
What you are getting for 1200 Euros is a machine that will separate tiny amounts of your compound mixtures, and give you a print out on a piece of paper. It's up to you to actually figure out what each single peak is. That's actually not an easy task at all, it's really really hard without a mass spec and fragment library and NMR.
Do you live near a University? Go to the chemistry department and ask for a tour of the analytical lab, or ask if someone can show you how to run a GC or something if you clean glassware for a week. If you have a more focused end goal, you can have a path more focused to the machines and techniques you'll learn to need.
On Mon, Sep 29, 2014 at 6:19 AM, Michele Stefanoli <michelestefanoli@gmail.com> wrote:
A last thing, sorry. So an old 50'60' gc doesn' imply expensive managment and parts are available at reasonable prices? A mass spectrometer is strongly recommended to analyze more analytes?
ThanksIl 28/set/2014 21:26 "Michele Stefanoli" <michelestefanoli@gmail.com> ha scritto:Thanks. Your tips are very appreciated. So I can have fun with fugal and plants estracts!
Il 28/set/2014 21:22 "Dakota Hamill" <dkotes@gmail.com> ha scritto:Save yourself the money. A GC is the last machine I'd recommend for steroid quantification. A LC MS/MS would be the gold standard, and those are $50,000+ (for the old ones). Not to mention consumables, gas tanks, regulators, solvent, and an actual lab space to do it in with dedicated high voltage lines.Body fluids generally require processing and are time sensitive and temperature sensitive depending on what you are testing for.Not to mention if you start handling anyone elses bodily fluids you'll need probably a handful of licenses and certifications.Honestly it sounds like an idea you haven't really thought out in the least bit.If I got an old GC i'd be playing with esters, ketones, and alcohols in studying perfumes or essential oil / flower extracts as they smell good (and it also means they are volatile and prime for a GC system).Standards are also probably cheap enough that you could at least use retention time of known controls to compare to what you have in a plant extract.I don't know where you live but some people are super into herbal extracts and things so I guess you could do GC runs of their sample mixtures and identify key chemical components. I can't imagine you'd get rich off of it though.--On Sun, Sep 28, 2014 at 3:02 PM, Michele Stefanoli <michelestefanoli@gmail.com> wrote:Not bought yet. Its only gc. I would study body fluids. Does the sample need long processing? Is possible to diagnose some conditions like detect hormones?
Il 28/set/2014 20:54 "Dakota Hamill" <dkotes@gmail.com> ha scritto:--You received this message because you are subscribed to a topic in the Google Groups "DIYbio" group.It can vary.Can you link the machine you bought? Or, make model and manufacturer?Did it come with software? Is it even working? Is it the really old kind that just uses a direct print-out?You'll need a carrier gas and collision gas, so you have to be somewhere where they'll even drop off nitrogen, air, or helium tanks.Actually just read it's a GC not a GCMS, so forget collision gasses. We had a GC from the 50's or 60's that still worked. Pretty simple. Turn on heat and carrier gas, inject, old school perforated print out, integrate peaks by hand.I find LC's to be 100x more useful than GC's, unless you are working with small organic molecules that are volatile.Did you have a specific class of metabolites you are wanting to look at with GC? Where are you going to find controls for your compounds?I guess the most important question is what are you even really trying to study?--On Sun, Sep 28, 2014 at 2:42 PM, biomiky <michelestefanoli@gmail.com> wrote:Hi folks!--Anybody knows how much costs in terms of consumables, capillary, tank, maintenance, solid phase... ecc a Gas Chromatography equipment?After buying a used one (found one for 1200 euros), who would be the stakeholders interested in the business? I would personally like to do some metabolomic research.ThanksBye
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