Optimization of hyphenated asymmetric flow field-flow fractionation for the analysis of silver nanoparticles in aqueous solutions

María Martínez-Cabanas,Eric P Achterberg,Felix Geißler,Pablo Lodeiro

doi:10.1007/s00216-021-03647-3

Abstract

The extensive use of silver nanoparticles (AgNPs) in consumer products, medicine, and industry leads to their release into the environment. Thus, a characterization of the concentration, size, fate, and toxicity of AgNPs under environmental conditions is required. In this study, we present the characterization and optimization of an asymmetric flow field-flow fractionation (AF4) system coupled with UV/Vis spectrophotometer and dynamic light scattering (DLS) detector as a powerful tool for the size separation and multi-parameter characterization of AgNPs in complex matrices. The hyphenated AF4-UV/Vis-DLS system was first characterized using individual injections of the different size fractions. We used electrostatically stabilized AgNPs of 20-, 50-, and 80-nm nominal diameters coated with lipoic acid. We investigated the effect of applied cross-flows, carrier solutions, focus times, and quantity of injected particles on the nature of the AF4 fractograms and on the integrity of the AgNPs. Best size separation of a 1:1 mixture of 20- and 80-nm AgNPs was achieved using cross-flows of 0.5 and 0.7 mL/min with 1 mM NaCl and 0.05% v/v Mucasol as carrier solutions. We also researched the behavior of AgNPs in natural waters using the hyphenated AF4-UV/Vis-DLS system, under determined optimal conditions.Graphical abstractSchematic and photograph of the AF4 setup with numbered hardware devices. Dashed lines represent electrical connections; continuous lines represent fluidic connections. For a better overview, not all fluidic connections between pump/6-way valve (2) and the Eclipse AF4 device (3) are shown in the schematic. The fluorescence detector (FL (7)) was not used in the study presented herein.

Highlights

Nanoparticles are materials with nanometric size, typically below 100 nm
Prior to the conceptualization of any AF4 size separation experiment, the AgNPs coated with lipoic acid were carefully characterized in terms of size distribution, polydispersity, and zeta-potential (Table 2) as well as their optical properties (Fig. 1)
This study showed that AF4 coupled with a multiparameter detection system can be a powerful tool to investigate the behavior and fate of nanoparticles in natural waters

Summary

Introduction

Nanoparticles are materials with nanometric size, typically below 100 nm. The small size of the nanoparticles, together with their large surface to volume ratio, leads to distinctive properties that make them different from the bulk material [1].Silver nanoparticles (AgNPs) are one of the most widely used nanoparticles, with a large range of applications [2]. Nanoparticles are materials with nanometric size, typically below 100 nm. The small size of the nanoparticles, together with their large surface to volume ratio, leads to distinctive properties that make them different from the bulk material [1]. Silver nanoparticles (AgNPs) are one of the most widely used nanoparticles, with a large range of applications [2]. The unique optical properties of the AgNPs are well known and make them useful for biosensing and imaging applications [3,4,5]. The AgNPs can be used in catalyzed reactions [6,7,8] and electronic applications [9,10,11]. The most common and widely utilized properties of AgNPs are

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