I use HCl to dissolve amino acids, can I dry the solution with freeze dryer?
Dear Xiaofang, I guess not. Hydrochloric acid is an aqueous solution of hydrogen chloride (which is a gas at NPT). As such most probably even before the water started to sublimate (freeze dry) the HCl would have been removed. Regards Luis
@Gouveia, thank you. Since HCL can be removed earlier than water then why it cannot be used with freeze-dryer?
Hi, I'm afraid I misinterpreted your question. Do you want to dry your AA's solutions, not the HCl, right? In that case I don't see why you cannot do it. Please let me know if this was the correct interpretation? Regards, Luis
@Gouveia, yes, sir, I want to dry my amino acids solution which the solvent is hydrochloric acid. I am not sure if it will damage the freeze dryer so I don't if I can use freeze dryer.
Hi, That's a difficult question for me to answer as I never tried. I advise you to read your freeze drier equipment user's guide just to check if there is some mention to it and/or to contact the manufacturer technical staff before actually trying. You could actually damage the condenser and the vacuum pump. I would appreciate if you share your findings in this forum. Regards, Luis
Yes of course you can. As long as the concentration of the HCl low and I think with amino acids you have used low concentration (0.1 M). I did that many times however make sure the freeze drier has a trap (Always ask before use). It is better to freeze your solution at -80oC for couple of hours. I would also suggest to use size exclusion column to remove the HCl and salts. You can use also the Cellulose (CF11) column with (4:1:1) butanol:water:acetic acid to remove the HCl.
@Naffa. Thank you, sir. I use GC MS to analyze amino acids, then I dissolve amino acids in 0.1M HCl. I want to dry HCl before derivatization.
While it CAN be done, it is not a good practice. The HCl vapors can damage the pump and react with the oil to cause permanent damage. I don't believe the condenser is cold enough to remove the acid, so it will pass through the system and into the pump, possibly even into the lab atmosphere. There are ways to neutralize the acid prior to freeze-drying, so I would try neutralization first.
Your question reminded me of the question, "Can I jump out of an airplane without a parachute?" The answer is "Yes, but only once."
Cool your solution down and put it under water vacuum until dry. Then freeze dry from water. I have jumped out of airplanes a few times. The plane was always on the ground. Best keep HCl away from metal parts. Most vacuum pumps use oil that can neutralize a small amount of acid.
Thank you, Jones. But we don't have underwater vacuum. I only have freeze-dryer.
That was a water vacuum pump. They are very lost cost pumps that connect up to water tap. Generally less than $20 USD
Consider that adduct may possibly form between amino acid and HCl. Concerning to either L-histidine or L-histidine hydrochloride monohydrate; see: https://www.researchgate.net/post/I-have-L-histidine-hydrochloride-monohydrate-Help-me-please-how-can-I-eliminate-HCl-and-water-molecule-to-obtain-L-histidine-only
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