In my lab, we compared different extraction strategies for quantitative metabolomics of breast cancer cells. The best results are obtained using methanol for quenching and methanol/CHCl3/H2O for extraction. The procedure is fully described here:

http://link.springer.com/article/10.1007%2Fs00216-011-5310-y

For Leishmania culture I´ve used ethanol/dry ice bath to quenching the metabolism. If you haven´t an appropriated thermometer, for a 10mL of medium ~3min. are suficient to drop the temperature to 2-4ºC.

Good Luck!!!

Look also Dewar BJ et al., 2010 and Folmes CD et al., 2011. For energy metabolites perchloric acid extraction is the best. Briefly, wash adherent cells with PBS, immerse dish into liquid nitrogen, layer on top HClO4, scrape cells, collect into Eppendorf tube and homogenize with plastic homogenizer, neutralize with KHCO3 above pH 7.0(!) , spin down and store extract at -20C.

We also use MeOH/CHCl3/H2O, although we then use GCMS

I would take some time to read this:

Duarte, I. F.; Marques, J.; Ladeirinha, A. F.; Rocha, C.; Lamego,

I.; Calheiros, R.; Silva, T. M.; Marques, M. P.; Melo, J. B.; Carreira, I.

M.; Gil, A. M. Analytical approaches toward successful human cell

metabolome studies by NMR spectroscopy. Anal. Chem. 2009, 81

(12), 5023−32.

This study investigated all the effects of different metabolite preparation routines. We prefer not to extract metabolites but instead obtain spectra of lyophilised and then rehydrated cells but this requires a HR-MAS probe.

Personally, the best way to rapidly quench any samples for any further mass spec analysis is use a dry ice-ethanol slurry. Then dip a tube containing you samples in that slurry and mix with a thermometer in order to avoid freezing of your cells at the bottom of the tube and check the temperature. When it reaches 8-10C, you cells have already reached 4C and metabolism is quenched. Then, you immediately transfer your tube on ice and carry on your metabolite extraction (at 4C the whole way). The quenching process should not take more than 2-3min. (Same method as what Juliano de Toledo mentioned above for Leischmania). This should answer quenching issues with any eukaryotic cells.

Just as Patrick said, cold methanol for quenching and CH3OH/CHCl3/H2O for extraction are a good combination and have been used in many labs.

I dip the petridish for 5 min in liquid nitrogen to stop all cellular activities and then extract metabolites in methanol /water solevnt

Liquid nitrogen is the most useful for quencing metabolism. 

Hi everyone, I have a question regarding quenching mammalian cells with liquid nitrogen. Do we need to worry about having liquid nitrogen touching the cells? Should we parafilm the plate to avoid this?

Don't worry. The idea is to freeze cells as quickly as possible. Parafilming plate can delay freezing.