Environmental context. The effects of engineered nanoparticles on the environment and on human health are difficult to evaluate largely because nanoparticles are so difficult to measure. The main problems are that concentrations are low and the engineered nanoparticles are often difficult to distinguish from the environmental matrices in which they are found. We report a separation technique that facilitates the detection of engineered nanoparticles in natural waters.Abstract. Few analytical techniques are presently able to detect and quantify engineered nanoparticles (ENPs) in the environment. The major challenges result from the complex matrices of environmental samples and the low concentrations at which the ENPs are expected to be found. Separation techniques such as asymmetric flow field flow fractionation (AF4) and more recently, hydrodynamic chromatography (HDC) have been used to partly resolve ENPs from their complex environmental matrices. In this paper, HDC was first coupled to light scattering detectors in order to develop a method that would allow the separation and detection of ENPs spiked into a natural water. Size fractionated samples were characterised using off-line detectors including analytical ultracentrifugation (AUC), dynamic light scattering (DLS) and single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). HDC was able to separate a complex mixture of polystyrene, silver and gold nanoparticles (radii of 60, 40, 20 and 10 nm) contained within a river water matrix. Furthermore, the feasibility of using HDC coupled to SP-ICP-MS was demonstrated by detecting 4 mg L À1 of a 20-nm (radius) nAg in a river water sample.

Engineered nanoparticles (ENP) are increasingly being incorporated into consumer products and reaching the environment at a growing rate. Unfortunately, few analytical techniques are available that allow the detection of ENP in complex environmental matrices. The major limitations with existing techniques are their relatively high detection limits and their inability to distinguish ENP from other chemical forms (e.g. ions, dissolved) or from natural colloids. Of the matrices that are considered to be a priority for method development, ENP are predicted to be found at relatively high concentrations in wastewaters and wastewater biosolids. In this paper, we demonstrate the capability of hydrodynamic chromatography (HDC) coupled to inductively coupled plasma mass spectrometry (ICPMS), in its classical and single particle modes (SP ICPMS), to identify ENP in wastewater influents and effluents. The paper first focuses on the detection of standard silver nanoparticles (Ag NP) and their mixtures, showing that significant dissolution of the Ag NP was likely to occur. For the Ag NP, detection limits of 0.03 μg L(-1) were found for the HDC ICPMS whereas 0.1 μg L(-1) was determined for the HDC SP ICPMS (based on results for the 80 nm Ag NP). In the second part of the paper, HDC ICPMS and HDC SP ICPMS were performed on some unspiked natural samples (wastewaters, river water). While nanosilver was below detection limits, it was possible to identify some (likely natural) Cu nanoparticles using the developed separation technology.