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

Abstract

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.

Identification of Blackberry (Rubus fruticosus) Volatiles as Drosophila suzukii Attractants

“…For the identification and quantification of the volatile compounds in R. fruticosus , four blackberries were analyzed using MHS-SPME GC-MS [ 30 , 31 , 32 ]. In total, 38 volatile compounds were identified in all samples, of which all except five that were not commercially available and another two that were highly volatile (ethanol and acetaldehyde) could be successfully quantified.…”

“…Using MHS-SPME GC-MS we identified a total of 38 volatile compounds, half of them were already identified in a different R. fruticosus cultivar using similar detection methods [ 39 ]. 33 of the 38 identified compounds were commercially available and tested for D. suzukii attractiveness [ 30 , 31 , 32 ]. This resulted in six individual compounds that significantly attracted D. suzukii : acetaldehyde, hexyl acetate, camphene, linalool, myrtenol and L -limonene.…”

“…There were four biological replicates, with each sample containing one berry. To identify and quantify the volatile compounds emitted by R. fruticosus , the berry samples were analyzed using MHS- SPME followed by GC-MS (MHS-SPME GC-MS) as in [ 30 , 31 , 32 ]. The sample was kept at 60 °C under agitation for 5 min using a TriPlus RSH Autosampler (Thermo Fisher Scientific, Waltham, MA, USA).…”

“…From each sample, volatiles were extracted and analyzed over fifteen consecutive runs, by which point most volatiles present in the blackberry sample were exhausted. This MHS-SPME GC-MS method (MHS-SPME GC-MS) allowed us to quantify the total amount of each volatile present in one berry [ 30 , 31 , 32 ].…”

“…To enable the development of more effective and selective lures for monitoring or mass trapping D. suzukii , the volatiles emitted by R. fruticosus were here identified and quantified using MHS-SPME (multiple headspace Solid Phase Micro Extraction) GC-MS, and the attractivity of the identified compounds to D. suzukii was studied. Although SPME is typically not used as a quantitative extraction technique, multiple consecutive extractions on the same sample (MHS-SPME GC-MS) have recently been shown to be an effective means to semi-quantitatively estimate the total amounts of different volatiles released by fruits, vegetables or other food [ 30 , 31 , 32 ]. All identified and commercially available compounds were subsequently tested for their attractivity to gravid D. suzukii females using two-choice laboratory bioassays.…”