Tools for Bark Biorefineries: Studies toward Improved Characterization of Lipophilic Lignocellulosic Extractives by Combining Supercritical Fluid and Gas Chromatography

Abstract

The bark of trees contains an interesting mixture of bioactive compounds, or so-called extractives. The use of supercritical carbon dioxide (sc-CO2) eliminates both the need for organic solvents as extractants and the danger that solvent traces might compromise the purity of the extracts. Unfortunately, the complexity and natural variability of extracts’ composition render any utilization attempts rather challenging. Thus, in order to implement exploitation concepts in a meaningful way, appropriate analytical techniques for characterizing extracts must be available beforehand. In our work, we explored gas chromatography coupled to both mass spectrometry and a flame ionization detector (GC-MS/FID), in combination with ultraperformance convergence chromatography and quadrupole time-of-flight mass spectrometry (UPC2-QTof-MS), for the characterization of bark extracts from pine (Pinus sylvestris L.) in both qualitative and quantitative terms. Although the conventional GC-MS/FID approach is a robust method for overall quantification of extractives, it fails to provide ample information about native sterol esters and triglycerides. These data are provided by a new, complementary analytical technique based on supercritical carbon dioxide, as the chromatographic eluant, coupled to a high-resolution mass spectrometer. The combination of both techniques and the use of sc-CO2 as both an extraction solvent and eluant made this combined tool especially powerful. The most prominent triglycerides in the extract were identified qualitatively and quantitatively, and the dominating sterol esters were identified qualitatively, by UPC2-QTof-MS.

Impact of residual extractives on the thermal stability of softwood Kraft pulp

“…Identification and quantification of extractives via gas-chromatography-mass spectrometry/flame ionization detector (GC-MS/FID) Extractives were quantified according to Barbini et al (2021). 3 to 5 mg of the dry extracts were accurately weighed in a 1.5 mL GC vial using an analytical balance.…”

Fate of Lipophilic Wood Extractives in Oxygen-Based Cellulose Bleaching

“…Next to already reported oxidation products of β-sitosterol obtained during ozone bleaching, many oxidized sterols remain unknown to date due to their inaccessibility to GC-MS. , The same holds true for less-volatile sterol esters and triglycerides, as well as their oxidation products. Thus, new and more sophisticated techniques are being developed. , The analysis of wood bark extractives with UPC 2 -ESI-QTof-MS has recently been introduced as a complementary technique to GC for the analysis of low-volatile and thermolabile compounds . The area of application was extended to the analysis of oxidation products that are formed during TCF bleaching and are too polar for established GC procedures.…”

“…Thus, new and more sophisticated techniques are being developed. 18,26 The analysis of wood bark extractives with UPC 2 -ESI-QTof-MS has recently been introduced as a complementary technique to GC for the analysis of low-volatile and thermolabile compounds. 18 The area of application was extended to the analysis of oxidation products that are formed during TCF bleaching and are too polar for established GC procedures.…”

“…18,26 The analysis of wood bark extractives with UPC 2 -ESI-QTof-MS has recently been introduced as a complementary technique to GC for the analysis of low-volatile and thermolabile compounds. 18 The area of application was extended to the analysis of oxidation products that are formed during TCF bleaching and are too polar for established GC procedures. This may be of great importance to the analysis of lipophilic compounds during the TCF bleaching of wood and nonwood pulp due to their tendency to cause deposits.…”

“…Additional information was gathered by in-source fragmentation and collision-induced dissociation (CID). The UPC 2 method was adopted from Barbini and slightly modified. Details of the sample preparation and analytical conditions can be found in the Supporting Information (SI Method M1–3).…”