Chromatography Forum

Hellow ,,


can any one suggest me in the separation between 2-Fluorophenyl acetic acid and phenyl acetic acid

Hellow ,,


can any one suggest me in the separation between 2-Fluorophenyl acetic acid and phenyl acetic acid

Hi,
For standart solution (K=2-5): Sil C18 (5mkm,C% 14-16), 0.05-0.1M AcOH aq. : MeCN 65- 60:35-40 v/v% or 0.025-0.05М KH2PO4 pH(aq.)=3.5-4.0(H3PO4) : MeCN 60-55:40-45 v/v% UV 254, 230 nm

Thanks for reply,,

I am using 0.05M NaH2PO4.H2O as buffer

Condition

Column : µ-Bondapak
eluent : Methanol : water[0.05M NaH2PO4.H2O , pH 4.0 by 10 % Aq. H3PO4 solution]
Polarity : Methanol [25%] : Buffer [75%]
wavelength : 210nm
Column Temperature : 40°c

Am I in right direction or not please suggest me

Thanks for reply,,

I am using 0.05M NaH2PO4.H2O as buffer

Condition

Column : µ-Bondapak
eluent : Methanol : water[0.05M NaH2PO4.H2O , pH 4.0 by 10 % Aq. H3PO4 solution]
Polarity : Methanol [25%] : Buffer [75%]
wavelength : 210nm
Column Temperature : 40°c

Am I in right direction or not please suggest me

Yes
But I think that better:
eluent: Methanol : aq. buffer 0.025M pH=3.5 (after mixing the pH is change) pH(eluent)<рКа(analit)!!!
Polarity: Methanol [30%] : Buffer [70%] v/v%
UV : 220nm, 230nm (you must find the absorption spectrum of these molecules)
Col. temp. : ambient or 30
Саn you send me chromatograms to virtulc@gmail.com

I suggest to go to a lower pH. Adjust with phosphoric acid to around pH 2.5 (measured in water). The retention of both analytes will increase a bit. You can compensate for this by adding a bit more methanol. I would also decrease the temperature to 30 degrees.

I also do not see the need for 210 nm. You will get less background (and better signal-to-noise ratio) by going to 254 nM or thereabouts.

Don't worry about any pH changes after you add the organic solvent. This is not important.