Monolithic capillary microextraction combined with ICP-MS for the determination of TiO2 NPs in environmental water samples

Increasing use of TiO2 nanoparticles (NPs) leads to an accumulation in environment and a risk to human. In this work, an on-line monolithic capillary microextraction (CME)-inductively coupled plasma mass spectrometry (ICP-MS) method was developed for sensitive determination of TiO2 NPs in environmental water samples. With the presence of citric acid, TiO2 NPs can be selectively adsorbed on the poly(acrylamide)-vinylpyridine-methylene bis-(acrylamide) (poly(AA-VP-Bis)) monolithic column at pH 1, whereas Ti ions cannot be adsorbed. Factors affecting the extraction efficiency such as sample pH, concentration of citric acid and elution conditions were carefully investigated. Under the optimum conditions, a detection limit of 0.63 μg L−1 for TiO2 NPs and a sample throughput of 6 h−1 were achieved. The method can be applied to the determination of TiO2 NPs in the size range of 5–100 nm. The developed method was then applied to the analysis of TiO2 NPs in the East Lake water and Yangtze River water, and recoveries of 84–109% were obtained for spiked samples. Compared with other reported methods for the determination of metal oxide NPs, the developed on-line monolithic CME-ICP-MS has the merits of simple operation, high throughput and no need for digestion before ICP-MS detection.