Earlier I have done GCMS using dried and crushed solid samples. But this is in liquid phase. So Im confused as to which protocol should I use? How to obtain the mixture in solvent form for doing GCMS?
If you have an oil-water mixture then you have a biphasic system, or two samples, not one. You start by separating your phases. Then, you analyze for whatever your analytes of interest are, keeping in mind that one phase is non-polar and the other phase is polar. There are multiple analytical protocols readily available on the Internet for free, and they take all of about 30 seconds to find. I'm pretty certain that it took you longer to post your question and read the responses than it would have to actually do your own research.
Tamali,
Because of the presence of water in the mixture, it should not be injected into GC-MS. You'll need to carry out the extraction of your analytes of interest in the mixture using chloroform or dichloromethane or a non-polar solvent which is not miscible with water. Afterwards, if you want to see what are in the aqueous phase, you will need to dry it down and derivatize it to facilitate GC analysis.
Hope this helps.
Dear Tamali
That depends on what you want to analyze the sample for. What type of compounds are you interested in? Polar or non-polar? Is your sample a two-phase system from the beginning? You need to make sure you have outlined all parameters and variables in the analysis before you start designing the protocol or looking for existing protocols.
You have to separate oil from water as the GC column is designed for volatile organic compounds in most of the case. You can do extraction as well as to remove the last bit with some chemicals which do not interfere your analysis.
Dear Tamali,
If you are measuring volatile compounds,
you can use head space/ Purge & Trap.
Dear Tamali,
Dr. Simon has outlined all the details that you need to begin with. I'd like to add a bit more. Since you mention supernatant, first question is how did you obtain it? For example, by centrifugation or chemical extraction. If chemical extraction, then the solvent used will give you a pretty good idea about the polarity of your targeted compound. Once you have that you can proceed with the design and optimization of a protocol.
Good luck.
If you have an oil-water mixture then you have a biphasic system, or two samples, not one. You start by separating your phases. Then, you analyze for whatever your analytes of interest are, keeping in mind that one phase is non-polar and the other phase is polar. There are multiple analytical protocols readily available on the Internet for free, and they take all of about 30 seconds to find. I'm pretty certain that it took you longer to post your question and read the responses than it would have to actually do your own research.
You didn't mention anywhere that what is your target compounds. Extraction depends on your target compounds. if you want to analyse the compounds present in your oil matrix then first you have to separate oil from water. You can separate your oil by using pet. spirit, hexane etc. You can also use ethyl acetate for separation, but there may be chance of loss of your target compounds. so first check best suitable solvent which should not be miscible with water, for your target compounds.
Stir Bar Sorptive Extraction (SBSE) involving a polydimethylsiloxane-coated stir bar with thermal desorption (TD), followed by gas chromatography coupled to mass spectrometry (GC–MS) analysis is a good protocol for aqueous samples for detection of compounds. I used SBSE technique in my previous study.
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