ONLINE SAMPLE CLEANUP OF FERMENTATION BROTHS AND SUBSTRATES PRIOR TO THE LIQUID-CHROMATOGRAPHIC SEPARATION OF CARBOHYDRATES

A coupled precolumn set-up is described for the clean-up of fermentation broths and substrates of hydrolysed lignocellulose prior to the analysis of carbohydrates. Matrix components cause severe problems owing to irreversible adsorption, increased back-pressure in the analytical column and interferences with the detection of the analytes. Sep-Pak (quaternary ammonium and amino) phases were used for the removal of brown reaction compounds and aldehydes. Non-polar (aromatic) compounds, phenolic acids and their derivatives and metal ions were removed using the hydrophobic polymer PLRP-S and a mixed cation-anion-exchange phase, respectively. Breakthrough volumes on the four precolumns were measured for fifteen model compounds normally present in hydrolysed lignocellulose. Applications to real samples illustrate the increased detectability in refractive index and UV detection and in detection systems using immobilized enzyme post-column reactors with UV and electrochemical detection.