Overview
ISO 23821:2022 - Cosmetics - Analytical methods - Determination of traces of mercury in cosmetics by atomic absorption spectrometry (AAS) cold vapour technology after pressure digestion provides a validated laboratory procedure for quantifying mercury in finished cosmetic products. The method combines pressure (microwave-assisted) digestion with cold vapour AAS (optionally using amalgam concentration) to achieve trace-level determination suitable for regulatory and quality-control testing.
Key technical topics and requirements
- Scope and principle
- Applicable to finished cosmetic products; digestion in closed vessels under pressure and heat (microwave-assisted) followed by cold vapour AAS measurement.
- Measurement at the mercury atomic absorption line 253.7 nm; reduction of Hg(II) to elemental mercury using reducing agents.
- Sample preparation
- Pressure digestion (microwave) at temperatures up to ~200 °C and pressures up to ~40 bar using mineral acids (nitric and hydrochloric).
- Filtration (membrane filter 0.45 µm) and preparation of measurement solutions with controlled acid content.
- Reagents
- Nitric acid, hydrochloric acid (stabilization recommended ≈ 1% HCl in solutions), reducing agents such as tin(II) chloride or sodium borohydride (freshly prepared; NaBH4 requires strict ventilation due to H2 evolution).
- Use certified mercury stock standards and matching acid-stabilized calibration solutions; prepare fresh daily.
- Instrumentation and cleaning
- Cold vapour AAS systems with cold vapour or amalgam (gold/platinum mesh) accessories; flow-injection alternatives supported.
- Rigorous decontamination of glassware (acid washes, ultrapure water) and use of low-contamination materials (borosilicate/quartz).
- Quality control and performance
- Calibration blanks, multiple calibration points, daily standard preparation.
- The standard includes procedures for limit of quantification (LOQ) assessment, quality control, and method reliability; method performance was validated by interlaboratory testing (ISO 5725 approach) and compared with ISO 23674.
Practical applications and users
- Laboratories performing cosmetic safety testing and compliance checks for mercury contamination.
- Manufacturers and quality-control teams verifying raw materials and finished products.
- Regulatory agencies and accredited testing bodies enforcing limits for mercury in cosmetics.
- Research labs conducting elemental analysis of cosmetic matrices.
Related standards
- ISO 23674 (parallel method; interlaboratory comparison documented)
- ISO 3696 (water for analytical laboratory use)
- ISO 5725 (statistical methods for method validation)
Keywords: ISO 23821:2022, mercury in cosmetics, cold vapour AAS, pressure digestion, microwave digestion, cosmetic testing, trace mercury analysis.