Quantitative analysis of odor-causing compounds in technical lignins by static headspace-gas chromatography with calibration by standard addition

The odor of lignin derived from industrial wood pulping is an obstacle to incorporating it into industrial processes to make value-added products from this renewable resource. However, the molecular cause of the odors remains poorly understood. This is in part due to a lack of analytical methods capable of accurately quantifying odor-causing volatile chemicals in lignin. In this research, a procedure was developed to quantify volatile compounds in lignin using a standard addition protocol to calibrate chromatographic data generated by static headspace gas chromatography/mass spectrometry. Lignin samples were equilibrated at 150 °C for 1 h prior to sampling for analysis. It was found that performing the headspace analysis at this temperature, above the glass transition temperature of the lignin, was critical to obtaining accurate results. Alternatively, the sample equilibration temperature could be lowered if the lignin was sufficiently dissolved in a solvent or softened by a plasticizer. In contrast, heating dry lignin at a temperature below its glass transition temperature does not result in full equilibration of present volatile compounds between the bulk sample and the vapor phase. These findings will help improve objective analysis of odor from lignin and aid in the development of processes to better control lignin odor.