I am trying to develop a GC analysis for Dimethylamine and Trimethylamine at the ppm level, and all I have to work with is GC with FID. Is there some sort of derivitization that I can do to make these compounds less volatile? HELP??????!!!???
By AllsepTech on Monday, April 5, 2004 - 09:39 pm:
Have you ever considered HPLC? I know that for some people it will sound strange, but if you make salt of dimethylamine and trimethylamine you will make then non-volatile (HCl or other). Secondary and tertiary amines have different pKa and you can separate them on our Primesep columns. You can try to use one of our methods for simple amines. Here are two links - first one for the separation of ammonia, methylamine, ethylamine, diethylamine by HPLC:
And method for triethylamine and trimethylamine:
Both methods might be applicable to your situation if your concentration is above 20 ppm. If it is less than 20 you can make salt of you amines and concentrate it. We have several other approaches to do this analysis (for low concentration analytes), contact via email or just call us
By Anonymous on Tuesday, April 6, 2004 - 05:22 am:
If all you have to work with is GC then are you trying to elute these from a capillary column? Don't use the wrong tool and blame the tool. Use a basic column that will retain the amines adequately. In other words, a packed column not based on silica. Most certainly, not a silica or silicone based capillary or packed column. Perhaps a PEG cap deactivated for bases might work, but stay away from silica and silicone phases if you want to see ppm levels of these amines.
By Anonymous on Tuesday, April 6, 2004 - 05:52 am:
With todays well deactivated columns amine analysis is not all that hard. J&W Scientific lists di and trimethylamine analysis on a 5 micron film of DB-1, 30 meter by 0.53 mm ID. You need to pay attention to your liner of course, must be well deactivated also but you should not have much trouble with ths analysis. Check out www.jandw.com (nope, don't work for them, just a satisfied user).
By YB on Tuesday, April 6, 2004 - 07:18 am:
Thank you all so much for your help, and quick responses. I have found a few applications for TMA/DMA by way of GC with FID, but I will have to do some sort of SPE if possible. These analytes are contaminants in an alkyltrimethyl ammonium chloride compound and "quats" tend to decompose in the GC, so I must extract the amines from the quat and then analyze by GC
By AllsepTech on Tuesday, April 6, 2004 - 07:39 am:
You do not have to use SPE, extraction or any other sample preparations for your sample if you use our Primesep column, like I said before you can use HPLC, your quat salts will retain on our column too. You can do one run to determine your free amines (trimethylamine and dimethylamine) and quaternary salts. Your quat will retain longer than amines due to higher PKa and hydrophobic properties.
By A.Mouse on Saturday, April 10, 2004 - 05:04 pm:
You can do the SPE on an ion-exchange cartridge. With a pH change from acidic to basic, you can elute the free amines, and the quaternary amine will stay.
You don't need to buy an HPLC because AllsepTech thinks you need one.