Real-world precision, bias, and between-laboratory variation for surface area measurement of a titanium dioxide nanomaterial in powder form

Accurate characterization of nanomaterial properties is a critical component of any nanotoxicology testing strategy. Data that describes the performance of various laboratories in measuring the characteristics of the same nanomaterial are scarce. We conducted an inter-laboratory study to evaluate real-world precision and bias of specific surface area measurements using a powered material containing sub-30 nm primary crystallites. Each participant was provided a sample of NIST Standard Reference Material 1898 (Titanium Dioxide Nanomaterial) and a sample preparation and analysis protocol. Based on results from 19 laboratories, overall performance was good. Estimates of precision ranged from 0.10 to 3.96 % and measurement bias was generally within +/- 5 % of the certified surface area value of the material. Between-laboratory variability accounted for 91 % of the total variance and is likely explained by gravimetric errors. Reliable determination of intrinsic nanomaterial properties such as surface area will permit development of protocols for toxicity testing, verification of laboratory proficiency, and consistency in interpretation of toxicity study data.