DescriptionInductively coupled plasma-mass spectrometry in single particle mode (single particle ICP-MS) has become a frequently used method for the detection and characterization of inorganic nanoparticles. The technique has been applied in our laboratory for studying inorganic nanoparticles in a variety of biological samples, including rat lung and liver tissue (gold and cerium oxide NPs), whale brain and liver tissue (mercury selenide NPs), human synovial fluid (cobalt and chromium-containing NPs) and human placenta tissue (silver NPs). Furthermore, food-related samples were investigated including lean chicken meat (silver NPs), game meet (lead NPs), food simulants (silver NPs), and noodles (aluminum-containing NPs).
We identified sample preparation as the most crucial step, especially in the case of solid / semi-solid matrices where simple dilution is not sufficient. As single particle ICP-MS analysis is not as sensitive as other analytical techniques, like field flow fractionation, to eventually remaining matrix residues, complete digestion of the matrix is usually not required. The main challenge is to minimize changes of the NPs during sample preparation mainly due to dissolution. For the majority of examples, we identified enzymatic digestion as the most suitable sample preparation method.
Our experiences show that single particle ICP-MS is a powerful screen method for the presence of NPs, but that care has to be taken with regards to false-positive-results and the obtained quantitative information in terms of particle size distribution and number / mass concentration. False positive results were obtained for two reasons: 1) Induced particle formation during sample preparation, e.g. from ionic species and 2) carry-over. For the latter case, we observed that analysis of ultrapure water between samples was not sufficient for evaluating carry-over, but that a realistic reagent or blank sample needs to be analyzed. Matrix-matching of calibration solutions was not possible in every case due to instability of the ionic species. In these cases, ionic standards had to be analyzed in ultrapure water or diluted acidic acid.
Based on our experiences, the talk will highlight the challenges and the “lessons learned” in relation to sample preparation for single particle ICP-MS, determination of transport efficiency, calibration, and data interpretation, and the next steps in the current and future work described.
|Period||23 Feb 2017|
|Event title||European Winter Conference on Plasma Spectrochemistry 2017|
|Location||Sankt Anton am Arlberg, Austria|
|Degree of Recognition||International|