Development of a combined SEM and ICP-MS approach for the qualitative and quantitative analyses of metal microparticles and sub-microparticles in food products

Abstract

An integrated approach based on the use of inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscopy (SEM) for the qualitative and quantitative analyses of metal particles in foods was devised and validated. Different raw materials and food products, like wheat, durum wheat, wheat flour, semolina, cookies, and pasta were considered. Attention was paid to the development of sample treatment protocols for each type of sample to avoid potential artifacts such as aggregation or agglomeration. The analytical protocols developed followed by ICP-MS and SEM investigations allowed us the quantitative determination and the morphological and dimensional characterization of metal nano- and microparticles isolated from the raw materials and finished food products considered. The ICP-MS method was validated in terms of linearity (0.8-80 μg/g and 0.09-9 μg/g for Fe and Ti, respectively), quantification limits (0.73 μg/g for Fe and 0.09 μg/g for Ti), repeatability (relative standard deviation (RSD) % equal to 10% for Fe and 20% in a wheat matrix as an example), and extraction recoveries (93 ± 2-101 ± 2%). Validation of the scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) measurements was performed working in a dimensional range from 1 to 100 μm with an estimated error in the size determination equal to 0.5 μm. ICP-MS data as well as SEM measurements showed a decrease in the concentration of metal particles from wheat to flour and from durum wheat to semolina samples, thus indicating an external contamination of grains by metal particles. These findings were confirmed by environmental SEM analysis, which allowed investigation of particles of lower dimensions. Generally, the largest number of particles was found in the case of iron and titanium, whereas particles of copper and zinc were only occasionally found without any possibility of quantifying their number.

Toxicity of Metal Oxide Nanoparticles: Mechanisms, Characterization, and Avoiding Experimental Artefacts

“…Measurements of tissue burden concentrations of nanomaterials and their released metal ions are typically performed using ICP‐OES/ICP‐MS analysis. Sample preparation however, introduces artefacts especially for complex samples such as biological tissue which requires digestion and filtration . Alternative methods are single particle ICP‐MS (SPICP‐MS) and asymmetrical flow field fractionation ICP‐MS (AF4‐ICP‐MS) .…”

Migration of Ti from nano-TiO2-polyethylene composite packaging into food simulants

“…To date, no direct evidence of the ingestion of nanomaterials resulting in harm to human health has been reported in the scientific literature. However, because the potential effects are not well understood, there are concerns about health and safety issues for consumers (Beltrami et al 2011).…”

Detection and characterisation of aluminium-containing nanoparticles in Chinese noodles by single particle ICP-MS

“…Higher concentrations (mean levels 5 to 10 µg/g) were often found in breads, cakes and pastries (with biscuits having the highest levels) and a majority of flours (EFSA 2008) The presence of inorganic nano-and microparticles in wheat and wheat-based products was shown in previous studies. Particles containing Fe or Ti in the size range between 1 to 10 µm were detected in durum wheat seeds, wheat seeds, semolina, wheat flour, biscuits and pasta samples by scanning electron microscopy (SEM) in A c c e p t e d M a n u s c r i p t combination with energy-dispersive X-ray spectroscopy (EDS) (Beltrami et al 2011).…”