I want to perform extraction of total lipids from feces and steroids from urine, and they needed to be transported to another country for the GC/MS analysis. Is it possible to totally dry these samples under nitrogen stream and transport them dried (without any solvent), and dissolve them upon arriving? Will this negatively affect the "quality" of my sample for the GC/MS? I will add BHT during extraction procedure, to prevent oxidation of lipids. Thank you in advance for help.
Dear Natasa,
Sounds like you have a plan. There should be no problem regarding the lipid stability and quality of extract if you add BHT in the extraction step and if yu then dry the extract before shipment.
In case samples are valuable I would advise shipping dry extracts in dry ice as well just in case there is a delay in delivery.
Hope this helps,
Ana
In your case of wanting to evaluate lipids in feces and steroids in urine there is another issue that may impact your analyses. In all feces, there is a significant quantity of microbial life. These microbes will not only contribute to the lipid content, but may also change the composition. For urine, there will likely be less microbial content, but these may change your sample as well. Also, many of the microbes will be anaerobic, which means that they can flourish in the absence of air, which is where you were heading with evaporating under nitrogen.
Addition of BHT to decrease the oxidation of the compounds is a good idea. However, getting the BHT distributed uniformly through the solid samples may be problematic.
I would suggest that you look into freeze drying the samples. With the near total dehydration of the samples in this case, under vacuum and frozen, the microbial activity will be significantly reduced. In the sample preparation process, dispersing the samples in water, will significantly reduce the variation in this process.
It is highly recommended that you evaluate the impact of the sample preparation and stabilization process in your laboratory with a number of samples to determine the impact of what ever processing you decide to go with, and to evaluate the changes in the samples over time to determine what level of impact can be expected over time. In other words, validate the process.
I agree with John Canham strongly based on lyophilization, freeze-drying suggestions. Antioxidant additives should be added for any method application whether it is chosen as nitrogen stream or vacuum concentrator or lyophilization. As an old, a little expensive but effective technique you may impregnate the solid-phase extraction sorbents with your extracts of interest as an alternative. This is a secure sample transport option but also a preliminary approach for sample prep if you can choose the resin accurately. Sealed 96 well-plate packed resins are a good option for uniform transport and sample preparation
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