Which brand of triethylamine is good enough for HPLC/UV?

[fatBrain]

I found that many commercially available triethylamine are very dirty, even those claimed as HPLC grade. Actually we can live with it when using isocratic. However, this problem is more serious when running gradient condition. Sometimes we can see huge peaks eluting when ramping up organic.

Thanks.

[DR]

Check your water. Most LC grade TEA is decent. Most water polishing systems (especially non-TOC units) leave just enough styrene monomer or dimer in the mix to cause the problem you describe, especially at lower wavelengths.

Empore Extraction disks (C-18 variety, made by 3-M, sold by Varian, among others) are a good solution. Rinse one w/ MeOH and run a liter of your water through, repeat until you have enough water to make your "A" phase. Try a blank gradient. If it's cleaner, your problem was the water, not the TEA.

[michaldousa]

The problem can not be due to triethylamine. I would try check the purity of water or organic solvent (especially at UV detection < 230 nm). The pH of mobile phase changes during gradient elution (in present of triethylamine, I do not know the concentration of TEA and gradient profile).

[syx]

Have you tried to run gradient system with and without TEA and compare the result?

[Mark Tracy]

Several years ago, I evaluated triethylamine from various sources to use in a DNA-snp assay. There were significant differences in the baseline, and the best one at the time was from Sigma and manufactured by Atofina. Of course, that was in the late 1990s, and things probably have changed.

[rhaefe]

I agree with Mark Tracy on that. Tested several different grades/manufacturers of triethylamine (around 1995-1996) and found significant differences. Finally settled for the distilled TEA from Fluka. Additional I stored it under nitrogen between uses.

Robert

[fatBrain]

Thanks for all the replies.

Water contamination, I didn't think about this possibility seriously before. The water system we use is a Nanopure Diamond UV ultrapure water system from Barnstead, which appears great to me. Maybe I should check it out while testing other TEA.

I did test one thing: use nanopure water as blank, and scan the UV spectrums of TEA solution, and ACN/water, and ACN/water/TEA. Not only did the TEA solution and ACN/water/TEA show strong absorbance at low wavelength (<230nm), but some modest absorbance at relative high wavelength as well, with a lambda max around 265 nm. ACN/water was just fine.

No matter what, it should be not a bad idea to test different TEA, as well as other possibility.

Thanks, all.