3 research outputs found
Capabilities of Single Particle Inductively Coupled Plasma Mass Spectrometry for the Size Measurement of Nanoparticles: A Case Study on Gold Nanoparticles
The increasing application
of engineered nanomaterials (ENMs) in
consumer and medical products has motivated the development of single-particle
inductively coupled plasma mass spectrometry (spICP-MS) for characterizing
nanoparticles under realistic environmental exposure conditions. Recent
studies have established a set of metrological criteria and evaluated
the feasibility of spICP-MS for sizing or quantifying various highly
commercialized ENMs. However, less is known about the performance
of spICP-MS for detecting nanoparticles with sizes greater than 80
nm. This paper presents a systematic study on spICP-MS for accurate
size measurement of gold nanoparticles from 10 to 200 nm. We show
that dwell time contributes significantly to the quality of data,
with the optimal dwell time that limits split particle events, particle
coincidences and false positives being 10 ms. A simple approach to
correct for split particle events is demonstrated. We show that transient
features of single particle events can be temporally resolved on a
conventional quadrupole ICP-MS system using a sufficiently short dwell
time (0.1 ms). We propose an intensity-size diagram for estimating
the linear dynamic size range and guiding the selection of ICP-MS
operating conditions. The linear dynamic size range of the ICP-MS
system under standard (highest) sensitivity conditions is 10 to 70
nm but can be further extended to 200 nm by operating in less sensitive
modes. Finally, the ability of spICP-MS to characterize heterogeneous
forms of metal containing nanoparticles is evaluated in mixtures containing
both dissolved and poly disperse nanoparticulate Au
Separation, Sizing, and Quantitation of Engineered Nanoparticles in an Organism Model Using Inductively Coupled Plasma Mass Spectrometry and Image Analysis
For
environmental studies assessing uptake of orally ingested engineered
nanoparticles (ENPs), a key step in ensuring accurate quantification
of ingested ENPs is efficient separation of the organism from ENPs
that are either nonspecifically adsorbed to the organism and/or suspended
in the dispersion following exposure. Here, we measure the uptake
of 30 and 60 nm gold nanoparticles (AuNPs) by the nematode, Caenorhabditis elegans, using a sucrose density gradient
centrifugation protocol to remove noningested AuNPs. Both conventional
inductively coupled plasma mass spectrometry (ICP-MS) and single particle
(sp)ÂICP-MS are utilized to measure the total mass and size distribution,
respectively, of ingested AuNPs. Scanning electron microscopy/energy-dispersive
X-ray spectroscopy (SEM/EDS) imaging confirmed that traditional nematode
washing procedures were ineffective at removing excess suspended and/or
adsorbed AuNPs after exposure. Water rinsing procedures had AuNP removal
efficiencies ranging from 57 to 97% and 22 to 83%, while the sucrose
density gradient procedure had removal efficiencies of 100 and 93
to 98%, respectively, for the 30 and 60 nm AuNP exposure conditions.
Quantification of total Au uptake was performed following acidic digestion
of nonexposed and Au-exposed nematodes, whereas an alkaline digestion
procedure was optimized for the liberation of ingested AuNPs for spICP-MS
characterization. Size distributions and particle number concentrations
were determined for AuNPs ingested by nematodes with corresponding
confirmation of nematode uptake <i>via</i> high-pressure
freezing/freeze substitution resin preparation and large-area SEM
imaging. Methods for the separation and <i>in vivo</i> quantification
of ENPs in multicellular organisms will facilitate robust studies
of ENP uptake, biotransformation, and hazard assessment in the environment
Development of a Standard Reference Material for Metabolomics Research
The
National Institute of Standards and Technology (NIST), in collaboration
with the National Institutes of Health (NIH), has developed a Standard
Reference Material (SRM) to support technology development in metabolomics
research. SRM 1950 Metabolites in Human Plasma is intended to have
metabolite concentrations that are representative of those found in
adult human plasma. The plasma used in the preparation of SRM 1950
was collected from both male and female donors, and donor ethnicity
targets were selected based upon the ethnic makeup of the U.S. population.
Metabolomics research is diverse in terms of both instrumentation
and scientific goals. This SRM was designed to apply broadly to the
field, not toward specific applications. Therefore, concentrations
of approximately 100 analytes, including amino acids, fatty acids,
trace elements, vitamins, hormones, selenoproteins, clinical markers,
and perfluorinated compounds (PFCs), were determined. Value assignment
measurements were performed by NIST and the Centers for Disease Control
and Prevention (CDC). SRM 1950 is the first reference material developed
specifically for metabolomics research