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This ISO TS specifies a test method for the detection and characterisation of nanoparticles in aqueous suspensions. Characterisation is specified here as the particle number and mass concentration and the number-based size distribution (assuming a spherical geometry of the individual particles).

The test method is applicable for the determination of the size of inorganic nanoparticles, metal and metal oxides (e.g. Ag, Au, TiO2 etc.), with size ranges of 10 nm to 100 nm in aqueous suspensions. Particle number concentrations that can be determined in aqueous suspensions range from 105 to 109 particles/L which corresponds (depending on the type of material) to mass concentrations in the range of 1 to 1,000 ng/L. Actual numbers depend on the type of mass spectrometer used and the type of nanoparticle analysed.

In addition to the particle concentrations, ionic concentrations can also be determined.

The test method is restricted to aqueous suspensions. The samples can be aqueous suspensions of the pure nanoparticles, aqueous extracts from materials or consumer products, aqueous digests of food or tissue samples, aqueous toxicological samples, or environmental water samples. Information about sample processing of non-aqueous samples can be found in the literature. Aqueous environmental samples are filtrated and diluted, food and toxicological samples are chemically or enzymatically digested and diluted. However, to relate particle number or mass concentrations in aqueous suspensions to the concentrations in the original sample requires information on extraction efficiency and matrix effects. Additional validation is required.

The method proposed in this document is not applicable for the detection and characterisation of organic or carbon-based nanoparticles like encapsulates, fullerenes and carbon nanotubes (CNT).