Chromatography Forum

Hi,

We are conducting a fenton experiment (H2O2/Fe (II) system) to study the degradation of 2-chlorophenol. We would like to analyze the reaction mixture on GCMS to see what are the oxidation products.

Before analysis we extract the reaction mixture, which is aqueous, with hexanes (it is a mix of 5 isomers). The extraction is conducted in a screw top glass vial and 9 mL of hexanes is used to extract 22 mL aqueous sample. The glass vial is then placed on a vortex mixer.

The problem is that the moment vortex starts a foam is formed in the hexane layer (extract) and it does not disappear even after 3 days.

Our guess for possible reasons for the formation of foams are:

1-The generation of O2 in the reaction mixture as a result of fenton reaction

2- Using the hexanes instead of n-hexane (which is normally used for liq-liq extraction)

I would really appreciate any insight regarding this issue.

Seyfollah

Is it possible for you to use solid-phase extraction to recover the reaction products? You might try that.

Foam formation in liquid-liquid extractions is not uncommon and it will most likely not be any different if you use n-hexane compared to hexanes.

2 tricks to have better separation between the 2 liquid phases: add some salt and/or heat the closed vial in an oven at ~80-90°C for 10min. In the latter case, be careful for pressure building up; you can use a cap with a rubber-like septum to visually monitor the pressure by expansion of the septum. Cool down the mixture before opening it.

I'm not sure if hexane is the best solvent to extract degradation products of chlorophenol. I'd choose a less apolar solvent: ethyl acetate, toluene, diethylether,... Or use a different sample preparation method like rb6banjo suggests.