I would like to do GC-MS analysis for metabolic profiling. In the protocol, it is said the standard such as Decanoic acids should be dissolved in 10 mg/mL Tetrahydrofuran. I have liquid Tetrahydrofuran that is 99.9% pure. How can I make 10 mg/mL concentration of that Tetrahydrofuran, which solvent I should consider?
Well, I think that the protocol says that you should make the solution of acids in THF with concentration of acids being 10 mg/ml, i.e. you put 10 mg of acids into 1 ml of THF. 99.9% is rather low purity. Cannot you buy pure for analysis THF? By the way, be careful with THF, before using it it will be good to check for THF peroxides. They are formed during THF storage, are explosive when heated and can oxidize many substances (e.g. unsaturated acids). Simple peroxides checking: make a solution of 0.5g V2O5 in 11 ml 98% H2SO4 and next carefully and very slowly add of water dist. to v= 500 ml. To a probe with 5 ml of THF add 1 ml of this solution. Brown colour + precipitate means that peroxides are present, yellowish clear solution - they are absent. To remove peroxides you can add to 1l THF about one spoon of copper (I) chloride, shake and leave for 24h. After that time check for peroxides, only when absent destilate THF but do not remove CuCl, pour this mixture together into a flask.
Well, I think that the protocol says that you should make the solution of acids in THF with concentration of acids being 10 mg/ml, i.e. you put 10 mg of acids into 1 ml of THF. 99.9% is rather low purity. Cannot you buy pure for analysis THF? By the way, be careful with THF, before using it it will be good to check for THF peroxides. They are formed during THF storage, are explosive when heated and can oxidize many substances (e.g. unsaturated acids). Simple peroxides checking: make a solution of 0.5g V2O5 in 11 ml 98% H2SO4 and next carefully and very slowly add of water dist. to v= 500 ml. To a probe with 5 ml of THF add 1 ml of this solution. Brown colour + precipitate means that peroxides are present, yellowish clear solution - they are absent. To remove peroxides you can add to 1l THF about one spoon of copper (I) chloride, shake and leave for 24h. After that time check for peroxides, only when absent destilate THF but do not remove CuCl, pour this mixture together into a flask.
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