Characterization Of Nanoparticle Size Using Asymmetrical Flow Field-Flow-Fractionation And Its Uncertainty Evaluation

Nanotechnolgy in materials and manufacturing, nano electronic and devices, environmental protection and energy, medicine and health, biotechnology and agriculture, aviation and aerospace are playing an inestimable role, and the characterization of nanoparticles is an indispensable means in the nanotechnology research. As a result of the increased use of nanoparticles as well as to draw reliable conclusions from nanotechnology studies, appropriate analytical techniques are of need. Indeed, numerous methods for the characterization of nanoparticles have been developed already. Common used techniques for size characterization are dynamic light scattering (DLS) and scanning/transmission electron microscopy (SEM, TEM, and STEM). However, the biased response of DLS for polydisperse samples toward larger particle size and the time and cost intensive investigations using electron microscopy and the measurements have to be performed under vacuum, limits the applicability of these methods, calling for alternative techniques which has the feature of separating particles gently, non-destructively, at high resolution with wide range. This paper first introduces the relevant theories of asymmetric flow field-flow fractionation, and asymmetric flow field-flow fractionation for the analysis and characterization of nanoparticles was developed. The void volume V0and the spacer thickness w of the channel are critical parameters for AF4behavior, which therefore were calibrated before method validation. Then, the AF4experimental parameters were optimized including the focusing time, cross flow rate, injection mass and detector flow rate, which are important to quantification. Then six kinds of polystyrene latexes were characterized through optimizing separation conditions, the results agreed well with certified mean diameter and deviations were less than10%. The uncertainty of AF4was evaluated and the uncertainty component which contributed to the uncertainty of AF4was considered. The characterization results of six standard polystyrene latexes and two unknown polystyrene latexes were compared with the results obtained by dynamic light scattering and scanning electron microscopy methods. Finally, in order to get the accurate size distribution, the influence of zone broadening of AF4was studied. The removal of zone broadening was studied in three kinds of methods which are the peak width theory, chromatographic theory and simulation method. The deviations from standard particle size distribution was larger using peak width theory and chromatographic theory. The deviation is very small within4.1%using simulation method. Therefore, we can obtain accurate particle size distribution through simulation method.