ISO 638-2:2022

Overview

ISO 638-2:2022 specifies an oven-drying method to determine the dry matter content of suspensions of cellulosic nanomaterials (CNMs). The procedure applies to CNM suspensions that contain only water and no appreciable amounts of other materials volatile at 105 °C ± 2 °C. The method yields the total dry matter (including dissolved solids); if only the cellulosic fraction is required, dissolved solids must be removed (e.g., washing or dialysis) before measurement.

Key topics and technical requirements

• Scope and principle: Weigh test specimens before and after drying to constant mass; dry at 105 °C ± 2 °C.
• Apparatus: analytical balance readable to 0.1 mg, water‑vapour-proof containers with tight lids (glass or compatible plastic), ventilated drying oven, and desiccator.
• Sampling & specimen prep:
  • Avoid filtration to concentrate dilute samples (risk of material loss).
  • Protect samples from evaporation and handle with gloves or tools.
  • Prepare at least duplicate specimens; ensure at least 20 mg of solid residue after drying (examples given for wt% concentrations).
  • Freeze‑drying (lyophilization) may be used for heat‑sensitive samples prior to oven drying.
• Drying procedure:
  • Establish container constant mass by repeated drying; container variation must be ≤ 1% of expected test specimen dry mass.
  • Initial drying time varies with volume but should not exceed 16 hours.
  • Constant mass achieved when successive weighings differ by ≤ 1% of specimen dry mass.
  • Parallel determinations should not deviate from the mean by more than 2%.
• Calculations & reporting: Dry matter content expressed as percentage (mass after drying / mass before drying × 100). Report sampling method and any pretreatment (e.g., dialysis).

Applications and users

ISO 638-2:2022 is intended for:

• Research laboratories analyzing cellulosic nanomaterials (nanocellulose, CNMs).
• QC and production labs in pulp, paper, and nanomaterials manufacturing.
• Analytical chemists performing concurrent chemical or physical tests that require accurate dry matter or moisture correction.
• Regulatory bodies and standards developers seeking harmonized test data.

Practical uses include batch release, formulation control, concentration determination for downstream testing, and ensuring consistent sample preparation for chemical/physical analyses.

Related standards

• ISO 638-1 (dry matter for solids)
• ISO 287 (moisture content of paper/board)
• ISO 4119 (stock concentration in suspensions)
• ISO 801 series (saleable mass) Referencing these helps ensure consistent moisture/dry-matter practices across paper, pulp and CNM testing.

Keywords: ISO 638-2:2022, dry matter content, cellulosic nanomaterials, oven-drying method, CNM suspensions, moisture determination, nanocellulose.