Overview
ISO 11212-4:1997 specifies a laboratory method for the determination of cadmium (Cd) content in starch and derived products using atomic absorption spectrometry (AAS) with electrothermal atomization (graphite furnace AAS). The standard covers sample preparation by wet digestion, instrument configuration, calibration and calculation of results expressed as micrograms of cadmium per kilogram of product.
Key topics and technical requirements
- Scope and definition: Cadmium content is reported as Cd (micrograms per kilogram) determined under conditions specified by the method.
- Sample preparation: Thorough homogenization followed by wet digestion of the organic matrix in a borosilicate digestion assembly (Soxhlet-type tube and round-bottom flask) using nitric acid and hydrogen peroxide.
- Instrumentation:
- High-resolution monochromator (≈0.2 nm bandwidth) and a cadmium hollow cathode lamp.
- Electrothermal atomizer: graphite tubular furnace with a pyrocoated Lvov platform and an inert atmosphere; automatic injection device recommended for repeatability and contamination control.
- Measurement at a wavelength of 228.8 nm.
- Reagents and standards:
- Analytical-grade nitric acid, hydrogen peroxide (30 %), and a palladium nitrate matrix modifier (1 g/L).
- Cadmium standard solution (1 g/L) and a set of at least five calibration solutions covering the working range.
- Analytical procedure:
- Injection of digested aliquots (with matrix modifier) into the furnace.
- Four-stage furnace program: drying, thermal pretreatment (ash/modify), atomization, and furnace cleaning - each stage must be optimized for the laboratory’s equipment.
- Calibration curve from standards; blank digestion required.
- Performance and quality:
- The standard notes a practical quantification capability when method conditions are strictly followed (the document indicates a quantification limit on the order of single micrograms per kilogram).
- Annex A summarizes interlaboratory precision data; ISO 5725 procedures were used to derive repeatability and reproducibility statistics.
Applications and users
ISO 11212-4:1997 is intended for:
- Food and starch manufacturers performing quality control and raw‑material testing.
- Analytical laboratories conducting heavy metals testing for compliance with food-safety and regulatory limits.
- Regulatory bodies and auditors verifying cadmium levels in starches, derivatives and by‑products.
- Laboratories experienced in graphite-furnace AAS that can optimize furnace programs and matrix modifiers for their equipment.
Related standards
- ISO 11212 (other parts): Part 1 (arsenic), Part 2 (mercury), Part 3 (lead) - all on heavy metals content in starch and derivatives.
- ISO 5725 - Precision of measurement methods (used for interlaboratory precision evaluation).
Keywords: ISO 11212-4:1997, cadmium determination, starch, graphite furnace AAS, electrothermal atomization, matrix modifier, palladium nitrate, calibration curve, heavy metals analysis.