A novel strategy for sequential analysis of gold nanoparticles and gold ions in water samples by combining magnetic solid phase extraction with inductively coupled plasma mass spectrometry

In this work, Al3+ immobilized Fe3O4@SiO2@iminodiacetic acid (IDA) was prepared and its extraction performance for gold nanoparticles (AuNPs) and gold ions (Au ions) was investigated. It was found that AuNPs and Au ions could be simultaneously retained on this adsorbent and their separation was achieved by sequential elution of Au ions and AuNPs with Na2S2O3 and NH3 center dot H2O, respectively. Based on it, a novel strategy by coupling magnetic solid phase extraction (MSPE) with inductively coupled plasma mass spectrometry (ICP-MS) was developed for the speciation of AuNPs and Au ions in environmental water samples. Various experimental parameters affecting MSPE of AuNPs and Au ions have been investigated carefully. AuNPs in a size range of 14-140 nm and with different coatings, including citrate, 11-mercaptoundecanoic acid (MUA), polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB), could be quantitatively determined by the proposed method. And the size and shape of the AuNPs were found to remain unchanged during the extraction process; thus the elution solutions could be directly introduced into ICP-MS without digestion. The developed MSPE-ICP-MS method has been applied in the analysis of AuNPs in natural water, sewage water and even sea water samples and Au ions in natural water samples with satisfactory results. Compared with the established methods for metal nanoparticle analysis, the developed method is more sensitive, faster, easier-to-operate, requires no digestion, and provides more valuable information for environmental monitoring and the assessment of nanoparticles' toxicity.