In this study, two commercial NP suspensions, polystyrene (PS) and TiO2, were employed and confirmed that the size were nanoscale using transmission electron microscopy (TEM) and dynamic light scattering (DLS). The conditions for preservation of nanoparticle samples were suggested to keep in 4oC without direct sunlight. The influence of natural parameters, large particles, pH, electrolyte, and humic acid, was investigated. It showed that the particle size became larger because of aggregation or sedimentation under pH close to the pHzpc of nanoparticles, with electrolytes or humic acid. Sampling the water without adjusment of pH to the pHzpc of nanoparticles and without adding electrolytes was recommened. To avoid the interference of pH, salts and humic substance, the samples were analyzed as soon as possible. Two pretreatment processes were introduced to eliminate the interference from large particles during the particle size analysis by DLS: centrifugation and hydrodynamic chromatography (HDC). Centrifugation (4060 G, 2 min) can be used to remove large particles efficiently. For the mixture of nano-PS and micro-TiO2, it was well separated by centrifugation and the recovery of nano-PS was 83%. For the mixture of nano-TiO2 and micro-SiO2, it was also well separated by centrifugation and the recovery of nano-TiO2 was 81%. The other novel technology applied in this area is HDC. To optimize the analysis, the deionized water adjusted to pH 10 was used as eluent to maintain the stability of TiO2 nanoparticles in HDC system. HDC can well separate two PS particles around 500 nm and 50 nm PS and the recovery of nano-PS was 87.1%. The accuracy, precision, repeatability and uncertainty of DLS and two pretreatments were evaluated and showed highly analytical qualities. The influences of three main aqueous parameters, pH, electrolyte, and humic acid, on nanomaterials in water were discussed. In contrast with PS, the obvious aggregatin and sedimentation behaviors were found when the aqueous pH value was close to the pHzpc of TiO2 NPs (~pH 4). Nevertheless, the particle size of PS was significantly changed when the concentration of NaCl up to 350 meq/L. The critical aggragation concentration (CAC) value of PS was near 500 meq/L. As compared to PS, TiO2 NPs were more easily aggragated at a lower NaCl concentration about 20 meq/L (CAC value). For humic acid, it did not affect the size of PS and TiO2 NPs. For the n-octanol-water partition coefficient (Kow), the Kow of nano-polystyrene is about 18.67. It’s revealed polystyrene prefers in the organic phase. The Kow of nano-TiO2 is 8.3×10-5, nano-TiO2 prefers in aqueous phase. Our results provide important insights into the ways in which nanoparticle analysis and change under different aqueous conditions, which is generally relevant to the nanoparticle measurement and fate in diverse natural environment.

engineered nanoparticles;dynamic light scattering;hydrodynamic chromatography;analytical technology;aggregation;sedimentation;stability;octanol-water partition coefficient