ISO 24215:2022

Overview

ISO 24215:2022 specifies a standardized laboratory method for determining the carbohydrate composition of lignin isolated from kraft pulping, soda pulping or biomass hydrolysis (biorefinery lignin). The method quantifies the five principal neutral monosaccharides - arabinose, galactose, glucose, mannose and xylose - to assess carbohydrate content and lignin purity. The procedure uses a two‑step sulfuric acid hydrolysis to release sugars, followed by separation and quantification by either ion chromatography (IC/PAD) or gas chromatography (GC/FID).

Key topics and technical requirements

• Scope and sample types: Applicable to kraft lignin, soda lignin and hydrolysis (biorefinery) lignins.
• Principle: Two-step sulfuric acid hydrolysis dissolves carbohydrates; acid‑insoluble lignin is filtered off and monosaccharides in the filtrate are analyzed.
• Analytical options:
  • IC with anion‑exchange column and pulsed amperometric detection (PAD) for direct monosaccharide measurement.
  • GC after reduction and acetylation (alditol acetates), analyzed by flame ionization detection (FID).
• Internal standard: 2‑deoxy‑galactose (or other specified internal standards) used to validate results.
• Sample preparation: Representative sampling (2–3 g air‑dry), optional resin extraction with petroleum ether, drying to constant mass (oven at 105 ± 2 °C), typical test specimen about 100 mg oven‑dried.
• Apparatus & reagents: Filtration crucibles, autoclave (≈120 °C), water bath, analytical balance, high‑purity reagents, sulfuric acid (72 %) and monosaccharide standards.
• Reporting & quality: Includes calculation method, precision information, and required test report content.

Applications and users

• Lignin producers and biorefineries use ISO 24215 to characterize lignin quality and carbohydrate contamination, guiding product specification and downstream processing.
• Pulp and paper industry labs employ the method for kraft and soda lignin evaluation.
• Research institutions and material developers (carbon fibre, adhesives, resins, thermoplastics, composites) apply carbohydrate composition data to predict performance and processing behavior.
• Quality control and certification bodies rely on standard methods for consistent, trade‑relevant lignin characterization.

Related standards

• ISO 21437 (related carbohydrate determinations in pulp) - method principles are similar though sample handling differs.
• ISO 14453 (referenced for petroleum‑ether resin extraction).
• TAPPI methods (e.g., T249) are noted as alternative derivatization procedures for GC when specified in reports.

This standardized test supports reliable lignin carbohydrate analysis, enabling consistent quality assessment across industrial and research laboratories involved in renewable‑material development.