By Anonymous on Tuesday, August 22, 2000 - 01:42 pm:
I am trying to analyze for residual TFA in a diacid (mp = 52C) using a RTx-1 column. I have settled on using acetone as a solvent and 1-pentanol as an internal standard. I have good stability over 24 hours of a 0.125 mg/mL TFA standard with the 1-Pentanol (conc. = 0.005 mg/mL). My linear regression (Peak area ratio with the IS) is 0.999 with conc. range of 0.025 to 0.25 mg/mL.
My problem lies in when I analyze the diacid, the first chromatogram produces the best response and the signal (FID) goes down by a factor of 2 with each successive injection. I am using a dilute and shoot technique and my sample conc. is 10 mg/mL. Extraction probably won't work since the solubility of the TFA and the diacid are very similar.
Anyone have any ideas on how to overcome this irreproducibility?
By Anonymous on Tuesday, January 9, 2001 - 05:00 pm:
a "hot" carboxylic acid plus an unhindered alcohol equals ester formation. chemistry is most likely the culprit.
Posting is currently disabled in this topic. Contact your discussion moderator for more information.