Overview
ISO 7252:1984 - "Paints and varnishes - Determination of total mercury - Flameless atomic absorption spectrometric method" - is a reference analytical method for measuring total mercury in paints and related products. The method is applicable to products with total mercury contents of about 0.01% (m/m) to 0.5% (m/m) and can be extended to higher concentrations with appropriate adjustments. It uses combustion of a weighed test portion, chemical reduction of mercury to the elemental form, entrainment of mercury vapor in a gas stream at ambient temperature, and quantification by cold vapour (flameless) atomic absorption spectrometry (AAS) at ~253.7 nm.
Key topics and technical requirements
- Scope and applicability: Reference method for paints and varnishes; typical range 0.01–0.5% (m/m), extendable above 0.5% with modified reagents and sample sizes.
- Analytical principle: Combustion in oxygen in a closed system → dissolution/reduction of Hg(II) to Hg(0) (SnCl2 reagent) → entrainment of Hg(0) into carrier gas → detection by AAS (cold vapour) at 253.7 nm.
- Essential reagents: commercial oxygen, tin(II) chloride in hydrochloric acid, 5% sulfuric acid, concentrated nitric acid, certified mercury standard solutions, and laboratory-grade water (ISO 3696 quality).
- Apparatus essentials: AAS spectrometer with mercury hollow‑cathode lamp, UV‑transparent measuring cell (optical path ≥100 mm), combustion flask with platinum sample holder, spark generator, flowmeter, diaphragm pump or compressed gas source, 4‑way reaction valve, anti‑condensation device for measuring cell, acid‑resistant tubing, and standard volumetric glassware.
- Procedure overview: Prepare calibration standards; combust a small sample (~20 mg in a gelatin capsule); collect and treat the combustion residues; reduce and transfer mercury vapor through the measuring cell; record peak height or area against standards; run blanks and duplicates; calculate total mercury content using the calibration result, dilution factor, sample mass and solution volumes.
- Quality control: Use reagent blanks, duplicate determinations, and calibration curve checks. Follow manufacturer instructions when using commercial mercury analysers based on the same principle.
Applications and users
- Routine and reference testing of paints, varnishes and related coatings for total mercury content.
- Used by: paint manufacturers, quality control and R&D laboratories, independent testing laboratories, environmental and regulatory bodies assessing mercury in coating products, and contract testing services.
Related standards
Keywords: ISO 7252, paints and varnishes, total mercury determination, flameless atomic absorption, cold vapour AAS, mercury analysis, paint testing, reference method.
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