Possibilities of single particle-ICP-MS for determining/characterizing titanium dioxide and silver nanoparticles in human urine

Abstract

Objective: The current use of nanoparticles in personal care and cosmetics, food safety, agriculture, medicine and pharmacy has led to a growing concern on the toxicity of these emerging materials to humans and also to the environment. Nanoparticles assessment (determination and size distribution) is a challenge mainly due to limitations of the current analytical instrumentation, but also because nanoparticles in foodstuff and environmental samples are usually found at low concentrations. The scenario is even more critical when dealing with clinical samples, mainly when trying to assess nanoparticles at basal levels in complex samples such as blood and urine. The aim of this paper is to find data regarding the presence of nanoparticles at basal levels in urine human samples.

Methods: The use of single particle - inductively couple plasma - mass spectrometry (sp-ICP-MS) has been explored to determine and characterize silver and titanium dioxide nanoparticles in human urine. Urine samples were directly diluted (1:5 to 1:10) with 1%(v/v) glycerol before sp-ICP-MS measurements, and efforts were made for validating the over-all procedure.

Results: The limit of detection and quantification for Ag NPs were 5.72 × 10³ and 1.91 × 10⁴ Ag NPs mL^-1, respectively; whereas, values for TiO₂ NP concentrations were 4.31 × 10³ and 1.44 × 10₄ TiO₂ NPs mL^-1. The limit of detection in size after applying several methods (3σ/5σ criteria) was found to be within the 8-9 nm for Ag NPs, and from 15 to 18 nm for TiO₂ NPs. Within-batch precision for Ag NP concentration was 15% (11% for mean size of nanoparticle distributions). Repeatability for TiO₂ NPs was 25% (TiO₂ NP concentration) and 9% (TiO₂ NP mean size). Good analytical recovery rates were found for spiked experiments with Ag NP standards of 40 and 60 nm (values within the 104-106% range), and also for TiO₂ NPs of 50 and 100 nm (96-98%). Finally, basal levels of Ag NPs and TiO₂ NPs, as well as total Ag and Ti concentrations, in human urine were assessed. Low Ag and Ag NP concentrations were found. Ag NPs exhibited mean sizes of approximately 16-17 nm. Total Ti levels, however, were higher than total Ag concentration, and TiO₂ NP concentrations within the 1.56 × 10⁴-2.80 × 10⁴ NPs mL^-1 range were measured (TiO₂ NP mean sizes were from 76 to 98 nm).

Keywords: Human urine; Silver nanoparticles; Single particle-inductively coupled mass spectrometry; Titanium dioxide nanoparticles.