Article pubs.acs.org/ac
Room Temperature Cation Exchange Reaction in Nanocrystals for Ultrasensitive Speciation Analysis of Silver Ions and Silver Nanoparticles Ke Huang,† Kailai Xu,† Jie Tang,† Lu Yang,§ Jingrong Zhou,† Xiandeng Hou,*,†,‡ and Chengbin Zheng*,† †
Key Laboratory of Green Chemistry and Technology of MOE, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, China ‡ Analytical & Testing Center, Sichuan University, Chengdu, Sichuan 610064, China § Chemical Metrology, Measurement Science and Standards, National Research Council Canada, Ottawa, Canada, K1A 0R6 S Supporting Information *
ABSTRACT: To evaluate the toxicity of silver nanoparticles (AgNPs) and Ag+ and gain deep insight into the transformation of AgNPs in the environment or organisms, ultrasensitive analytical methods are needed for their speciation analysis. About 40-fold of Cd2+ in CdTe ionic nanocrystals can be “bombarded-and-exploded” (exchanged) in less than 1 min simply by mixing the nanocrystals with Ag+ solution at room temperature, while this cation exchange reaction did not occur when only silver nanoparticles were present. On the basis of this striking difference, an ultrasensitive method was developed for speciation analysis of Ag+ and AgNPs in complex matrices. The released Cd2+ was reduced to its volatile species by sodium tetrahydroborate, which was separated and swept to an inductively coupled plasma mass spectrometer (ICPMS) or an atomic fluorescence spectrometer (AFS) for the indirect but ultrasensitive detection of Ag+. Owing to the remarkable signal amplification via the cation exchange reaction and the advantages of chemical vapor generation for sampling, the limit of detection was 0.0003 μg L−1 for Ag+ by ICPMS, which was improved by 100-fold compared to the conventional method. Relative standard deviations are better than 2.5% at a concentration of 0.5 μg L−1 Ag+ or AgNPs regardless of the detector. The proposed method retains several unique advantages, including ultrahigh sensitivity, speciation analysis, simplicity and being organic reagent-free, and has been successfully utilized for speciation analysis of Ag+ and AgNPs in environmental water samples and paramecium cells.
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the skin or pass through the cell membrane to interact with DNA or important enzymes. Yin et al.13 found that the toxic effect of AgNPs on Lolium multif lorum was higher than that arising from Ag+. To distinguish the toxicity of AgNPs and Ag+ and gain deep insight into the transformation of AgNPs in the environment or organisms, it is desired to develop novel analytical methods for speciation analysis of Ag+ and AgNPs in samples with complex matrices. Like elemental speciation analysis, the most practical approach for speciation analysis of Ag+ and AgNPs is to hyphenate a powerful separation technique to a sensitive atomic spectrometric detector, for example, micellar electrokinetic chromatography (MEC),15 reversed-phase liquid chromatography (RPLC),16 or field flow fractionation (FFF) coupled to inductively coupled plasma mass spectrometry (ICPMS).17,18 Although these hyphenated techniques are powerful since they provide more size and shape
mong consumer products related to nanomaterials, silver nanoparticles (AgNPs) containing products are the most numerous because of their excellent antibacterial activity and have been widely used in various fields including textiles, food containers, and medical devices.1,2 Their rapidly growing use inevitably releases large amounts of AgNPs to the environment and may cause environmental problems.3,4 Despite increasing interest in their environmental effect and biological toxicity of AgNPs over the past several years,5−8 the mechanisms of AgNPs toxicity remain largely in a state of “discussion” due to the complicated nature of the transformation and toxicology of AgNPs after entering organisms. In order to accurately evaluate AgNPs toxicity, Navarro et al.9 found that addition of cysteine to complex with Ag+ can remove the toxic effect and concluded that the toxicity of AgNPs was mainly from the Ag ions and AgNPs might only act as sources of Ag+. Recently, Xiu et al.10 have also reported that Ag+ exhibited much more antimicrobial activity than AgNPs, and the latter were even not toxic to bacteria in many cases. On the contrary, in some previous studies,11−14 it was observed that AgNPs could easily penetrate © XXXX American Chemical Society
Received: February 7, 2015 Accepted: May 28, 2015
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DOI: 10.1021/acs.analchem.5b00511 Anal. Chem. XXXX, XXX, XXX−XXX
Article
Analytical Chemistry
speciation analysis of Ag+ and AgNPs, owing to the magic cation amplification by the CER and the high analyte transport efficiency and efficient matrix separation of the CVG.38−40
information, there remain other respective drawbacks besides the common shortcomings of complex interface, possibly unsatisfactory limits of detection (LODs), laborious sample preparation, or high instrumental cost in hyphenation and maintenance. For MEC/RPLC, the interaction between AgNPs and the stationary or mobile phase may result in the size and shape change and reduction of lifetime of a chromatographic column. Although FFF can be used as an alternative to partially overcome the disadvantages of MEC/RPLC, simultaneous speciation analysis of AgNPs and Ag+ is conventionally not easy. Speciation analysis of AgNPs and Ag+ could also be achieved by adapting separation methods. As an emerging and promising analytical technique, single particle ICPMS allows not only speciation analysis of AgNPs with different size but also simultaneous determination of the dissolved Ag+.19−22 Despite this method retaining several unique advantages, such as fast data acquisition and high throughput, the minimum detectable particle size of a sliver nanoparticle is about 20 nm. This means that the AgNPs with smaller size (
