Standardization and validation of a protocol of size measurements by dynamic light scattering for monodispersed stable nanomaterial characterization

• A methodology to validate protocols of size measurement by DLS was proposed.
• A validation of 2 protocols was achieved using 2 standards at 60 and 203 nm.
• Protocols were found robust, accurate and consistent with standard ISO.
• Expanded uncertainties were less than 10% for measurements performed at 25 °C.
• Protocols were suitable to determine the size of monodispersed nanomaterials.

Among physico-chemical properties used to characterize nanomaterials, size and size distribution are essential. Several methods are suitable to evaluate these characteristics including the well-established method based on dynamic light scattering (DLS). Size measurement protocols have been rarely standardized or totally validated. However, there is a need for having standardized and validated protocols for the characterization of nanomaterials due to the pressure of authorities interested by the evaluation of risk assessments on nanomaterials that are introduced in increasing number of applications. Standardization is paramount to provide comparable values between different laboratories. This paper proposes a standardization of two protocols for evaluating the size of nanomaterials by DLS at 20 and 25 °C and a methodology to achieve their validation by investigating their robustness, precision and trueness using appropriate certified reference materials including standards of 60 and 203 nm whose assigned values were traceable to the International System of Units. Data were interpreted using specifically designed methods of analysis of variance ANOVA. Uncertainties of protocols proposed in the present work were 7.0 and 3.8% for dispersions at 60 and 203 nm respectively at temperature of measurement of 20 °C and 6.8 and 3.8% for dispersions at 60 and 203 nm respectively at temperature of measurement of 25 °C. These values attested that both protocols give reliable size measurements of diverse nanomaterials.

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