Methods for separation, identification, characterization and quantification of silver nanoparticles Jing-fu Liu, Su-juan Yu, Yong-guang Yin, Jing-bo Chao There is a growing production and application of silver nanoparticles (AgNPs) (e.g., in cosmetics products, food technology, textiles and fabrics, and medical products and devices). The rapid growth in the commercial use of AgNPs will inevitably increase exposure to silver in the environment and among the general population. Compared to the vast application of silver, information on the fate, the transformation and the toxicity of AgNPs is very limited. Lack of proper techniques to trace AgNPs in complex matrixes hinders investigation. Thus, development of methods for analysis of AgNPs is very important to achieve detailed insights into the fate, the transport and exposure of AgNPs in environment. This review presents state-of-the-art methods for separation, identification, characterization and quantification of AgNPs. We also discuss perspectives on future developments. ª 2012 Elsevier Ltd. All rights reserved. Keywords: Characterization; Cloud-point extraction; Environmental exposure; Field-flow fractionation; Human exposure; Identification; Nanomaterial; Separation; Silver nanoparticle; Toxicity 1. Introduction Silver nanomaterials (NMs) (nanosilvers) are clusters of silver atoms of 1–100 nm in at least one dimension. Due to their un- ique physical and chemical properties, nanosilvers are widely used in various areas with exponentially increasing pro- duction. Apart from traditional usage in the engineering industry {e.g., catalysis, optical devices, surface plasmon resonance (SPR), surface-enhanced Ramon spectros- copy (SERS) and electronic applications [1]}, excellent antibacterial activity made them popular in a widespread range of applications (e.g., fabrics, disinfectants and medical devices). Nanosilvers represent a broad spectrum of antimicrobial activity, and can kill both Gram-positive and Gram-negative bacteria (e.g., Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Staphylococcus aureus) [2,3]. It is also reported that nanosilvers have a great bactericidal effect on multidrug -resistant bacteria. The activity of nano- silvers was examined on different drug- resistant pathogens of clinical importance, including multidrug-resistant Pseudomo- nas aeruginosa, ampicillin-resistant E. coli O157:H7 and erythromycin-resistant Strep- tococcus pyogenes [4]. It was shown that nanosilvers could inhibit the growth rate of bacteria from the initial contact with the pathogens, and had their antibacterial activity by killing bacteria rather than by the bacteriostatic mechanism. Nanosilvers also have antifungal activ- ity. They could inhibit a series of ordinary fungal strains, including Aspergillus fumigatus, Mucor, Candida albicans, Candida glabrata, Candida tropicalis, Saccharomyces cerevisiae, and Aspergillus fumigatus [5]. The antiviral properties of silver nano- particles (AgNPs) are also reported in the literature. A notable example is anti-HIV-1 activity. A study [6] revealed that AgNPs prepared in Hepes buffer could inhibit HIV-1 replication, and the anti-HIV activity was much higher than that of gold Jing-fu Liu*, Su-juan Yu, Yong-guang Yin, Jing-bo Chao State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China * Corresponding author. Tel./fax: +86 10 62849192; E-mail: jfliu@rcees.ac.cn Trends in Analytical Chemistry, Vol. 33, 2012 Trends 0165-9936/$ - see front matter ª 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.trac.2011.10.010 95