Overview
ISO 1762:2019 specifies a standardized method for determining residue (ash content) on ignition at 525 °C for paper, board, pulps and cellulose nanomaterials. The procedure measures inorganic matter remaining after controlled incineration and is applicable to all types of these materials. The standard aims to deliver high-precision results (down to 0.01% or better) and includes specific guidance for sampling, sample preparation, incineration and result expression.
Key topics and requirements
- Scope: Residue (ash) determination at 525 °C ± 25 °C; cellulose nanomaterials are defined as cellulose nano-objects with dimensions ~1–100 nm.
- Precision target: Measurement precision of 0.01% or better.
- Sample mass: Test specimen should be at least 1 g (dry basis); residue ideally ≥ 10 mg and preferably > 20 mg for improved precision. For very low-ash samples, multiple aliquots may be incinerated consecutively in the same crucible.
- Moisture/dry matter: Moisture or dry matter content must be measured separately (refer ISO 287 or ISO 638) and used to report ash on a dry basis.
- Apparatus:
- Muffle furnace capable of 525 °C ± 25 °C (venting recommended).
- Heat‑resistant crucibles (platinum, porcelain, silica); platinum recommended for very low residues.
- Analytical balance with readability of 0.1 mg or better.
- Sampling & preparation:
- Use ISO 186 (paper/board) and ISO 7213 (pulps) guidance for representative sampling.
- For cellulose nanomaterials, dry suspensions by appropriate methods (heating at 105 °C, freeze-drying or spray-drying) and homogenize before subsampling. Filtration of dilute suspensions is not recommended.
- Be aware that chemically modified nanomaterials can carry cations that affect ash content.
- Safety: The document highlights nanomaterial handling precautions and best laboratory practices.
Applications and users
- Quality control and acceptance testing in paper mills, pulp producers, coating & filler manufacturers.
- Analytical laboratories performing routine or comparative ash content analyses.
- Researchers and manufacturers of cellulose nanomaterials (nanocellulose, CNC, CNF) assessing inorganic content, surface modification residues or manufacturing contaminants.
- Regulatory and materials characterization contexts where a reproducible inorganic-content metric at 525 °C is required.
Related standards
- ISO 2144 - Determination of ash at 900 °C (alternative temperature).
- ISO 186 - Sampling of paper and board.
- ISO 287 / ISO 638 - Moisture and dry matter determination.
- ISO 7213 - Sampling for pulps.
- ISO/TS 20477 - Terminology and guidance on cellulose nanomaterials.
ISO 1762:2019 provides a reliable, reproducible method for quantifying inorganic residue in cellulosic materials - essential for product specification, process control and research where ash content at 525 °C is a critical parameter.