U.S. Environmental Protection Agency, National Exposure Research Laboratory, Environmental Sciences Division, 944 E. Harmon Avenue, Las Vegas, Nevada 89119, USA.
Anal Chem. 2012 Aug 7;84(15):6454-62. doi: 10.1021/ac300302j. Epub 2012 Jul 16.
Nanoparticle (NP) determination has recently gained considerable interest since a growing number of engineered NPs are being used in commercial products. As a result, their potential to enter the environment and biological systems is increasing. In this study, we report on the development of a hyphenated analytical technique for the detection and characterization of metal-containing NPs, i.e., their metal mass fraction, size, and number concentration. Hydrodynamic chromatography (HDC), suitable for sizing NPs within the range of 5 to 300 nm, was coupled online to inductively coupled plasma mass spectrometry (ICPMS), providing for an extremely selective and sensitive analytical tool for the detection of NPs. However, a serious drawback when operating the ICPMS in its conventional mode is that it does not provide data regarding NP number concentrations and, thus, any information about the metal mass fraction of individual NPs. To address this limitation, we developed single particle (SP) ICPMS coupled online to HDC as an analytical approach suitable for simultaneously determining NP size, NP number concentration, and NP metal content. Gold (Au) NPs of various sizes were used as the model system. To achieve such characterization metrics, three calibrations were required and used to convert ICPMS signal spikes into NPs injected, NP retention time on the HDC column to NP size, and ions detected per signal spike or per NP to metal content in each NP. Two calibration experiments were required in order to make all three calibrations. Also, contour plots were constructed in order to provide for a convenient and most informative viewing of this data. An example of this novel analytical approach was demonstrated for the analysis of Au NPs that had been spiked into drinking water at the ng Au L(-1) level. The described technique gave limits of detection for 60 nm Au NPs of approximately 2.2 ng Au L(-1) or expressed in terms of NP number concentrations of 600 Au NPs mL(-1). These were obtained while the 60 nm NPs exhibited a retention time of 771 s at a mobile phase flow rate of 1 mL min(-1).
纳米颗粒（NP）的测定最近引起了相当大的关注，因为越来越多的工程纳米颗粒被用于商业产品。因此，它们进入环境和生物系统的潜力正在增加。在这项研究中，我们报告了一种用于检测和表征含金属纳米颗粒的分析技术的发展，即它们的金属质量分数、尺寸和数浓度。适用于 5 至 300nm 范围内纳米颗粒尺寸测定的水力色谱（HDC）在线与电感耦合等离子体质谱（ICPMS）偶联，为纳米颗粒的检测提供了一种极其选择性和灵敏的分析工具。然而，当 ICPMS 以其传统模式运行时，一个严重的缺点是它不能提供关于 NP 数浓度的数据，因此，关于单个 NP 的金属质量分数的任何信息都无法获得。为了解决这个限制，我们开发了在线与 HDC 偶联的单颗粒（SP）ICPMS，作为一种适合同时测定 NP 尺寸、NP 数浓度和 NP 金属含量的分析方法。各种尺寸的金（Au）纳米颗粒被用作模型系统。为了实现这种特征化度量，需要进行三次校准，并用于将 ICPMS 信号尖峰转换为注入的 NP、在 HDC 柱上保留的 NP 时间到 NP 尺寸，以及每个信号尖峰或每个 NP 中检测到的离子到每个 NP 中的金属含量。为了进行所有三次校准，需要进行两次校准实验。此外，还构建了等高线图，以便为这种数据的方便和最直观的查看提供便利。以将 Au NPs 加入饮用水中至 ng Au L(-1) 水平的分析为例，展示了这种新的分析方法。该技术对 60nm Au NPs 的检出限约为 2.2ng Au L(-1)，或用 600Au NPs mL(-1) 表示的 NP 数浓度表示。当以 1ml min(-1) 的流动相流速保留 60nm NPs 时，获得了这些检出限。
