Overview
ISO 10775:2013 specifies an atomic absorption spectrometric procedure for the determination of trace cadmium in all types of paper, board and pulp that can be wet-combusted in nitric acid. The method uses wet combustion (autoclave or microwave) followed by graphite-furnace AAS with a L'vov platform. Typical lower determination limits depend on instrumentation but are normally about 10 µg/kg. Cadmium locked in pigments or fillers that do not dissolve in the nitric-acid digestion may not be measured quantitatively.
Key Topics
- Scope and limits: Covers paper, board and pulps including recycled-fibre products; notes incomplete dissolution for some pigments/fillers.
- Sample preparation: Representative sampling (see ISO 186 / ISO 7213), moisture/dry-matter correction (ISO 287 / ISO 638), avoidance of contamination (use foil, non-metal tools).
- Wet combustion:
- Autoclave: PTFE vessels in a heating block at 160 ± 5 °C for 16 ± 1 h, 1 g test portions typical.
- Microwave digestion: PTFE digestion vessels with safety valves; adjust test portion (e.g., max 0.3 g for 120 ml vessel).
- Reagents and standards: Use high-purity reagents; concentrated HNO3 (c = 15 mol/l) and dilute HNO3 (0.15 mol/l). Cadmium calibration stocks and working solutions are prepared as specified.
- Instrumental determination: Graphite-furnace AAS with background correction recommended. Use standard additions to control matrix effects or a validated calibration curve when matrix interferences are absent.
- Matrix modifiers: Typical modifiers include palladium nitrate, ammonium dihydrogenphosphate, or magnesium nitrate; choice depends on lab performance and blank checks.
- Quality control: Run blanks, duplicates, and reference materials; check matrix effects and adjust acid concentration of standards to match samples.
Applications
- Routine laboratory testing for trace cadmium in paper, board and pulp for regulatory compliance, product safety and environmental monitoring.
- Quality control in paper manufacturing, especially where recycled fibres are used and trace-metal monitoring is required.
- Method validation and interlaboratory comparisons for laboratories using graphite-furnace AAS for trace-metal analysis.
Related Standards
- ISO 186 - Paper and board: sampling to determine average quality
- ISO 287 - Determination of moisture content (oven-drying)
- ISO 638 - Determination of dry matter content (oven-drying)
- ISO 7213 - Pulps: sampling for testing
Practical value: ISO 10775:2013 provides a reproducible, documented workflow (sample handling, wet combustion, calibration and AAS measurement) to obtain reliable cadmium results in paper-related matrices while highlighting limitations where cadmium is bound in insoluble pigments or fillers.