Analysis of Silver Nanoparticles in Ground Beef by Single Particle Inductively Coupled PlasmaMass Spectrometry (SP-ICP-MS)

The regulation and characterization of nanomaterials in foods are of great interest due to the potential risks associated with their exposure and the increasing number of applications where they are used within the food industry. One factor limiting the scientifically rigorous regulation of nanoparticles in foods is the lack of standardized procedures for the extraction of nanoparticles (NPs) from complex matrices without alteration of their physico-chemical properties. To this end, we tested and optimized two sample preparation approaches (enzymatic- and alkaline-based hydrolyses) in order to extract 40 nm of Ag NP, following their equilibration with a fatty ground beef matrix. NPs were characterized using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Fast sample processing times (<20 min) were achieved using ultrasonication to accelerate the matrix degradation. NP losses during the sample preparation were minimized by optimizing the choice of enzymes/chemicals, the use of surfactants, and the product concentration and sonication. The alkaline approach using TMAH (tetramethylammonium hydroxide) was found to have the highest recoveries (over 90%); however, processed samples were found to be less stable than the samples processed using an enzymatic digestion based upon pork pancreatin and lipase (approximate to 60 % recovery). Low method detection limits (MDLs) of 4.8 x 10(6) particles g(-1) with a size detection limit (SDL) of 10.9 nm were achieved for the enzymatic extraction whereas an MDL of 5.7 x 10(7) particles g(-1) and an SDL of 10.5 nm were obtained for the alkaline hydrolysis.