Overview
ISO 9795:2023 specifies analytical methods for determining the inorganics content in lignin products - specifically kraft lignin, soda lignin and hydrolysis lignin. The standard defines when to use ash content (residue on ignition) and when to determine the sum of major inorganic elements for accurate quantification. It is intended for laboratories and industry stakeholders performing lignin characterization and quality control for bio-based materials.
Key topics and technical requirements
- Scope and sample types: Applicable to lignin isolated from kraft and soda pulping processes and lignin obtained by hydrolysis of biomass.
- Two measurement approaches:
- Ash method (acid-form kraft, soda and hydrolysis lignin): Determine residue on ignition at 525 °C ± 25 °C and express inorganics as ash on a dry basis.
- Elemental method (kraft lignin in base form): Ash the sample, dissolve residue in ~6 mol/L HCl, and measure seven major elements - sodium, calcium, potassium, magnesium, iron, manganese, copper - by ICP/ES. The inorganics content is the sum of these element amounts.
- Analytical notes:
- Only acid‑soluble metals are determined; acid‑insoluble species (e.g., silicates) require digestion or fusion (see ISO 17812).
- Alternative detection techniques (e.g., ICP‑MS, AAS) may be used if validated.
- Supporting procedures and materials: Dry matter determination per ISO 6350; laboratory water quality per ISO 3696; reagent-grade acids and certified element standards.
- Precision and reporting: The standard includes precision information, calculation and expression of results, and required test-report content.
Applications and who uses ISO 9795:2023
- Pulp & paper mills and lignin producers for product specification and process control.
- Analytical laboratories performing routine testing of lignin feedstocks.
- Manufacturers of bio-based products - e.g., solid fuels, phenolic resins, polyurethane foams, thermoplastics, carbon fibre - where low or well-characterized inorganic content is critical (e.g., ash limits for lime kilns or carbon-fibre feedstocks).
- R&D organizations developing lignin valorization routes and needing reliable inorganic-content data for formulation and performance assessment.
Related standards
ISO 9795:2023 provides clear, industry-relevant methods for accurate determination of lignin inorganics content - essential for quality control, regulatory compliance, and optimized use of lignin in bio-based applications.