Lignin Quantification of Papyri by TGA—Not a Good Idea

Abstract

Papyri belong to the oldest writing grounds in history. Their conservation is of the highest importance in preserving our cultural heritage, which is best achieved based on an extensive knowledge of the materials’ constituents to choose a tailored conservation approach. Thermogravimetric Analysis (TGA) has been widely employed to quantify cellulose and lignin in papyrus sheets, yielding reported lignin contents of 25% to 40%. In this work, the TGA method conventionally used for papyrus samples was repeated and compared to other lignin determination approaches (Klason-lignin and acetyl bromide-soluble lignin). TGA can lead to a large overestimation of the lignin content of commercial papyrus sheets (~27%) compared to the other methods (~5%). A similar overestimation of the lignin content was found for the pith and rind of the native papyrus plant. We concluded that the TGA method should, therefore, not be used for lignin quantification.

Ultrasonic Microwave-Assisted Micelle Combined with Fungal Pretreatment of Eucommia ulmoides Leaves Significantly Improved the Extraction Efficiency of Total Flavonoids and Gutta-Percha

“…The content of lignin in the sample was determined by Klason method [32]. In short, the sample and the mixture of ethanol and benzene were extracted for 6 h by Soxhlet extractor.…”

Lignin-based acrylate adhesive without organic solvent processing

“…[40][41][42] The mass loss of MAL was higher than AL, with a trend of increasing mass loss of MAL with increasing MC dosage, which is because MC consumes the hydroxyl groups, weakening the intramolecular hydrogen bonds, thus destabilizing them. 43,44…”

Methods and Materials of Making Ancient and Modern Papyrus Sheets: A review.

“…Papyrus plants are comprised of roots, rhizomes, a triangular stem and flowers; their taxonomy, description and distribution are well documented [6,12]. The chemical compositions of lignin in pith and rinds of papyrus plants were characterized [13]; white pith from the stem contains 54-60 % cellulose (C6H10O5)n and 36-40 % lignin (C81H92O28) [14], however lignin forms only ~5 % of modern, commercial papyrus sheets and 16 % of papyrus pith [15]. Papyrus stems contain hydrocarbons, fatty acids, 2-hydroxyfatty acids, fatty alcohols, phytol and phytol esters, alkylamides, monoand diglycerides, steroids (sterols, ketones, hydrocarbons, esters and glycosides), tocopherols and tocopheryl esters, alkyl ferulates, ω-carboxyalkyl ferulates (and their monoglycerides), and acylglycerol glycosides [16].…”