Column = Thermoscientific hypersil gold column
Mobile phase = 0.005M H2SO4 (pH 2.1),
Temperature = 45oC,
Flow rate = 0.6ml/min
Detector = refractometer.
Acetic acid standards concentrations = between 0.02-0.5mg/ml.
Injection volume = 20ul.
Run time = 15min.
There's usually a huge negative peak continuing into a positive peak (6.5 min retention time) whose height increases with increased concentration of acetic acid. However, the peak shape and retention times are not constant. Any suggestions from anyone who has encountered this?
I would not use the reversed phasae mode to do this because it is not selective enough. I would recommend to use ion exchange or ion-exlcusion method. Check out this site http://www.shimadzu.com/an/hplc/support/lib/lctalk/54/54intro.html or look at my paper long time ago J. of Chrom 536 (1991)193-201. Or send me your e-mail and I will forward to use. I try to attach the file here but it does not work.
Agree with Narong Chamkasem.
I would recommend a column usually called "organic acid" offered under brand names like: Prevail, Acclaim, Rezex etc. The columns separate very nice a sort of organic as well as some inorganic anions by ion-exclusion mechanism while running with simple 100% aqueous mobile phase eg. 25 mM KH2PO4 pH 2,5. With addition of some organics you can alter selectivity towards more hydrophobic analytes.
Thank you all for your suggestions. I'm now working on using an ion-exclusion column and UV detection at 210nm. the peaks are better, but still have shoulders. I'll optimize the mobile phase appropriately.
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