Characterization of Klason lignins by reversed-phase high-performance liquid chromatography using wide-pore octadecylsilica and stepwise gradients of dimethylformamide in water

Abstract

RP-HPLC using stepwise gradients of N,N-dimethylformamide (DMF) in a phosphate-buffered (pH 3.00) aqueous mobile phase and a wide-pore (30 nm) octadecylsilica column has been applied to the analysis of a variety of lignins--organocell lignin, dioxane lignin, Björkman lignin, and Klason lignins from both softwoods and hardwoods, respectively, in order to demonstrate the usefulness of the approach for their characterization. Tandem combination of spectrophotometric diode array detection and fluorimetric detection was used to acquire more detailed information about the chromatographic behavior of lignins. The results show that a ten-step gradient can reveal distinct features of lignins and humic substances. Combination of good solvating properties of DMF for lignins together with a wide-pore RP sorbent improves surface interactions of the analytes and suppresses the influence of size exclusion effects. Thus it provides reproducibility of characterization profiles and robustness of the method. The calculated repeatability of the retention time of selected peaks was +/- 0.46% RSD. The reproducibility of the data within one week (set of seven data) was +/- 1.1% RSD. These data are also representative of the other well-shaped peaks of analyzed substances.

Polar Aprotic Modifiers for Chromatographic Separation and Back-Exchange Reduction for Protein Hydrogen/Deuterium Exchange Monitored by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…The ProZap C 18 column with 40% DMF resulted in high back-pressure (>25 MPa) [52] and could not be used. Poor separation was noted even at a lower flow rate.…”

Unmodified kraft lignin isolated at room temperature from aqueous solution for preparation of highly flexible transparent polyurethane coatings

“…The catalytic activity of tertiary amines closely parallels to the base strength of the amines except when steric hindrance becomes pronounced. [48][49][50] In our studies, catalytic effects could even be observed inuencing the PU coating quality, in particular the homogeneity of the coating surface. In general, tertiary amines inuence the crosslinking density thereby also improving the coating stability, an effect also observed by other groups.…”

Recent innovations in analytical methods for the qualitative and quantitative assessment of lignin

“…While chromatographic methods are often employed in conjunction with wet chemical methodology, a few instrumental developments probing lignin structure are worth discussing [44,[52][53][54][55][56]. Aromatic lignin compounds, derived from naturally and artificially aged paper were identified using capillary zone electrophoresis (CZE) [52].…”

“…Despite the preferential reaction of p-CAT with SA, higher S lignin content was not detected in plants with elevated p-CA content. Isolated lignins from various hardand softwood feedstocks were partitioned and characterized using a reverse phase-HPLC instrument equipped with a wide-pore octadecylsilica column [53]. The authors determined that a 10-step gradient using N,N-dimethylformamide and fluorimetric detection enabled well-defined lignin peaks.…”

“…Ultimately, reproducible, in situ measurements of lignin structure have been coveted for decades. Lignin structure Functionality specific reactions [40][41][42][43][44][47][48][49][50] CZE [52] APPI-MS [67] CRS Microscopy [116,117] AFM [178] GC [44] DFT [88,180] GCMS [171] DE-MS [62] Dispersive Raman [92][93][94][95][96] DSC [60] ClO 2 [45] GLC-FID [54] ESI/MS [77] Potentiometry [44] Modified oximation [46] GLC-MS [54] MALDI-MSI [68] Ellipsometry [179] Headspace GC [55] SEM [71,75] MALDI/TOF [73] Fluorescence [102,103,120,131,176,177] TEM [103] RP-HPLC [53] MBMS [75] FTIR [13,44,…”