With the increasing use of nanotechnology in food and consumer products, there is a need for reliable detection and characterization methods for nanoparticles (NPs) in complex matrices. NPs often interact with each other or with their surroundings leading to aggregation, adhesion to surfaces or dissolution in dispersion solvents. Accurate and precise characterization of metrics such as size, shape, particle mass and number concentration therefore remains a challenging analytical task.
In order to determine quantitative metrics that are relevant in food monitoring or in risk assessment, asymmetric flow field flow fractionation (AF4) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS) has proven to be a powerful technique [1]. In order to acquire accurate data the AF4 separation method and settings must be optimized for each new sample matrix and analyte NP combination [1,2]. Furthermore, additional information obtained by an imaging method such as transmission electron microscopy (TEM) proved to be necessary for trouble shooting and for independent verification of results.
An AF4-ICP-MS method was developed for the separation, detection and characterization of silver nanoparticles (AgNPs) in chicken meat. AgNPs are presently one of the most frequently used nanomaterials in consumer products related to food, such as food storage containers and dietary supplements. Aqueous and enzymatic extraction strategies were tested to liberate the AgNPs from the meat matrix into liquid suspension. The resulting AF4-ICP-MS fractograms, which corresponded to the enzymatic digests, showed a major nano-peak (about 80 % recovery) plus smaller peaks that eluted close to the void volume of the fractograms. In order to gain further insight into the sizes of the separated AgNPs, or their possible dissolved state, fractions of the eluate were collected and subjected to ICP-MS analysis in single particle (sp) mode. As a second example an AF4-ICP-MS method for the detection and characterization of silicon dioxide NPs in tomato soup will be presented.
Finally, the possibility of using alkaline pre-treatment of biological tissue prior to sp-ICP-MS analysis of their content of gold nanoparticles (AuNPs) was tested and compared with enzymatic sample preparation [3]. The results showed that the same results, with respect to the obtained number-based size distribution for AuNPs, were obtained for the two preparation methods. In contrast, the alkaline method was superior for quantification of AuNPs and was comparable with that obtained by ICP-MS after digestion of the samples in aqua regia.
[1] K. Loeschner, J. Navratilova, S. Legros, S. Wagner, R. Grombe, J. Snell, F. von der Kammer, and E.H. Larsen, J. Chrom. A., 1272, 116 (2013).
[2] K. Loeschner, J. Navratilova, C. Købler, K. Mølhave, S. Wagner, F. von der Kammer, and E.H. Larsen, Anal. Bioanal. Chem., 405, 8185 (2013).
[3] K. Loeschner, M. Brabrand, J. Sloth, and E.H. Larsen, Anal. Bioanal. Chem., Epub ahead of print, DOI: 10.1007/s00216-013-7431-y (2013).
| Period | 7 May 2014 |
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| Event title | 5th International IUPAC Symposium for Trace Elements in Food |
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| Event type | Conference |
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| Conference number | 5 |
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| Location | Copenhagen, DenmarkShow on map |
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