First steps towards a generic sample preparation scheme for inorganic engineered nanoparticles in a complex matrix for detection, characterization, and quantification by asymmetric flow-field flow fractionation coupled to multi-angle light scattering and ICP-MS

The applicability of a multi-step generic procedure to systematically develop sample preparation methods for the detection, characterization, and quantification of inorganic engineered nanoparticles (ENPs) in a complex matrix was successfully demonstrated. The research focused on the optimization of the sample preparation, aiming to achieve a complete separation of ENPs from a complex matrix without altering the ENP size distribution and with minimal loss of ENPs. The separated ENPs were detected and further characterized in terms of particle size distribution and quantified in terms of elemental mass content by asymmetric flow-field flow fractionation coupled to a multi-angle light scattering detector and an inductively coupled plasma mass spectrometer. Following the proposed generic procedure SiO2-ENPs were separated from a tomato soup. Two potential sample preparation methods were tested these being acid digestion and colloidal extraction. With the developed method a complete SiO2-ENPs and matrix separation with a Si mass recovery >90% was achieved by acid digestion. The alteration of the particle size distribution was minimized by particle stabilization. The generic procedure which also provides quality criteria for method development is urgently needed for standardized and systematic development of procedures for separation of ENPs from a complex matrix. The chosen analytical technique was shown to be suitable for detecting SiO2-ENPs in a complex food matrix like tomato soup and may therefore be extended to monitor the existence of ENPs during production and safety control of foodstuffs, food labelling, and compliance with legislative limits

Does the determination of inorganic arsenic in rice depend on the method?

In answering a request from the Directorate General for Health and Consumers of the European Commission, the European Union Reference Laboratory for Heavy Metals in Feed and Food, with the support of the International Measurement Evaluation Program, organized a proficiency test (PT), IMEP-107, on the determination of total and inorganic arsenic (As) in rice. The main aim of this PT was to judge the state of the art of analytical capability for the determination of total and inorganic As in rice. For this reason, participation in this exercise was open to laboratories from all over the world. Some 98 laboratories reported results for total As and 32 for inorganic As. The main conclusions of IMEP-107 were that the concentration of inorganic As determined in rice does not depend on the analytical method applied and that introduction of a maximum level for inorganic As in rice should not be postponed because of analytical concerns.JRC.DG.D.6-Food Safety and Qualit

Feasibility of the development of reference materials for the detection of Ag nanoparticles in food: neat dispersions and spiked chicken meat

The feasibility of producing colloidal silver nanoparticle reference materials and silver nanoparticle spiked reference matrix materials was investigated. Two concentrations of PVP-coated silver nanoparticle dispersions were evaluated and used to spike chicken meat, with the aim of producing a set of reference materials to support the development of analytical methods for the detection and quantification of nanoparticles in food. Aqueous silver nanoparticle (AgNP) dispersions were evaluated for their homogeneity of mass fraction and particle size and found sufficiently homogeneous to be used as reference materials. Stability studies at 4 °C, 18 °C and 60 °C demonstrated sufficient short- and long-term stability, although particle size decreases in a linear fashion at 60 °C. The AgNP dispersions were characterized for total Ag mass fraction by ICP-OES, dissolved Ag content by ultrafiltration-ICP-MS, as well as AgNP particle size by dynamic light scattering, transmission electron microscopy (TEM) and gas-phase electrophoretic molecular mobility analysis. Chicken breasts were homogenized by cryo-milling and spiked with aqueous AgNP dispersions. Rapid freezing over liquid nitrogen resulted in homogeneous and stable materials. The spiked chicken materials were characterized for their total Ag mass fraction by neutron activation analysis and for the AgNP particle size by TEM and single-particle inductively coupled plasma mass spectrometry. The observed differences in particle sizes between the spiked chicken samples and the original silver dispersions indicate relevant matrix effects. The materials demonstrate that production and characterization of reference materials for the detection and quantification of silver nanoparticles in meat are feasible, but challenges especially in assessing stability and having sufficiently precise methods for assessment of homogeneity and stability remain

Validation of methods for the detection and quantification of engineered nanoparticles in food

The potential impact of nanomaterials on the environment and on human health has already triggered legislation requiring labelling of products containing nanoparticles. However, so far, no validated analytical methods for the implementation of this legislation exist. This paper outlines a generic approach for the validation of methods for detection and quantification of nanoparticles in food samples. It proposes validation of identity, selectivity, precision, working range, limit of detection and robustness, bearing in mind that each “result” must include information about the chemical identity, particle size and mass or particle number concentration. This has an impact on testing for selectivity and trueness, which also must take these aspects into consideration. Selectivity must not only be tested against matrix constituents and other nanoparticles, but it shall also be tested whether the methods apply equally well to particles of different suppliers. In trueness testing, information whether the particle size distribution has changed during analysis is required. Results are largely expected to follow normal distributions due to the expected high number of particles. An approach of estimating measurement uncertainties from the validation data is given