Hi,

I am trying to analyse the fatty acid composition of rhamnolipids and sophorolipids using GC-MS. For this, I have obtained FAMEs of the glycolipids after hydrolysis with acidic methanol*. The analysis revealed the presence of FAMEs without any hydroxyl groups along with the expected FAMEs containing 3-hydroxy (for Rhamnolipids) and 17- hydroxy (for Sophorolipids) groups. Is it a regular observation or pertains to specific cases?

*Procedure: Methanol containing 1% sulphuric acid (2 ml) was added to approximately 50 mg of the sample and heated at 100 ºC for 40 min. The reaction product was then extracted with 5 ml of cyclohexane with 5 ml of 50 g/l NaCl. The cyclohexane layer was then dried under a stream of nitrogen.

For GCMS: The injection temperature was set at 275 ºC and column oven temperature at 65 ºC for 5 min ramping at 10 ºC /min to 290 ºC and the final hold was given for 5 min. MS scan range was 10-350 with ion source temperature at 200 ºC.

Thanks