Quantification of Volatiles from Technical Lignins by Multiple Headspace Sampling-Solid-Phase Microextraction-Gas Chromatography-Mass Spectrometry

Industrial lignins comprise a mixture of substances, including volatile, low-molecular weight compounds. In material applications of lignins, these volatiles contribute to the malodor of the finished product. We developed a method based on solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) to assay qualitatively and quantitatively the volatiles emitted from lignin samples. Substances were identified by mass spectra and retention indices, while quantitation was achieved by multiple headspace sampling (MHS). Guaiacol and dimethyl disulfide were calibrated as representative compounds for the most prominent substance classes. The method was validated and gave good recovery, ranging from 89 to 123% for dimethyl disulfide and 90 to 105% for guaiacol, a measurement range of several dozen nanogram to a few micrograms, which can be extended by adjusting the sample amount, and limits of detection of 86 ng for dimethyl disulfide and 25 ng for guaiacol. Sample preparation is limited to weighing of the sample into a headspace vial and requires no consumables or auxiliaries. The entire analytical workflow was automatized, including the necessary data evaluation, which combines the outcome of repeated analyses of the same sample. The concentrations of guaiacol in four representative lignin samples ranged from 0.4 to 1200 ppm, while dimethyl disulfide was detected only in a single sample.