Conventional Inductively Coupled Plasma Mass Spectrometry Research Articles

An Unprecedented Metal Distribution in Silica Nanoparticles Determined by Single-Particle Inductively Coupled Plasma Mass Spectrometry.

Metal-containing nanoparticles are now common in applications ranging from catalysts to biomarkers. However, little research has focused on per-particle metal content in multicomponent nanoparticles. In this work, we used single-particle inductively coupled plasma mass spectrometry (ICP-MS) to determine the per-particle metal content of silica nanoparticles doped with tris(2,2'-bipyridyl)ruthenium(II). Monodispersed silica nanoparticles with varied Ru doping levels were prepared using a water-in-oil microemulsion method. These nanoparticles were characterized using common bulk-sample methods such as absorbance spectroscopy and conventional ICP-MS, and also with single-particle ICP-MS. The results showed that averaged concentrations of metal dopant measured per-particle by single-particle ICP-MS were consistent with the bulk-sample methods over a wide range of dopant levels. However, the per-particle amount of metal varied greatly and did not adhere to the usual Gaussian distribution encountered with one-component nanoparticles, such as gold or silver. Instead, the amount of metal dopant per silica particle showed an unexpected geometric distribution regardless of the prepared doping levels. The results indicate that an unusual metal dispersal mechanism is taking place during the microemulsion synthesis, and they challenge a common assumption that doped silica nanoparticles have the same metal content as the average measured by bulk-sample methods.

A Single-Step Digestion for the Quantification and Characterization of Trace Particulate Silica Content in Biological Matrices Using Single Particle Inductively Coupled Plasma-Mass Spectrometry.

The increased use of amorphous silica nanoparticles (SiNPs) in food products, materials science, cosmetics, and pharmaceuticals has raised questions about potential hazards in the environment and in human health. Although SiNPs are generally thought to be benign, recent studies have demonstrated toxicity in different cell and animal models. Despite their ubiquitous use, SiNPs are rarely analyzed quantitatively. Often, the methods used to analyze silicon and SiNPs are difficult, costly, require the use of dangerous reagents, and are prone to interferences. Additionally, characterization of SiNPs in complex matrices requires extensive sample preparation. To address this, we propose a single-step digestion method for the determination of trace SiNP content in biological matrices. For conventional inductively coupled plasma-mass spectrometry (ICP-MS) analysis, biological samples are often digested with concentrated HNO3. We found that with conventional ICP-MS, lower limits of detection (LLOD) of silicon are too high for trace analysis. However, we found that SiNPs are stable at a strong acidic pH; thus, concentrated HNO3 could be used to digest biological samples leaving SiNPs intact. Then, by analysis with single particle ICP-MS, we found that the smallest SiNP that could be read was 185nm in size. The concentration for the LLOD was found to be 0.032ppb with interday variability in sizing and concentration at 2.5% and 6.8% respectively. Utilizing this method, SiNPs were accurately sized and counted in cell pellets and media. Our proposed method can be used to accurately quantify and characterize SiNPs (or agglomerated SiNPs) larger than the derived LLOD in a variety of biological matrices and will assist in determining relationships between exposures of SiNPs and toxicity in humans and the environment.

Risk of overestimation of urinary cadmium concentrations: interference from molybdenum

We show here that the selection of analytical method is critical when measuring low levels of cadmium in human urine. Cadmium is today usually analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), which has a higher sensitivity than Atomic Absorption Spectroscopy (AAS). ICP-MS cadmium measurements show interference from tin ( 114 Sn) and molybdenum oxides, which can result in an overestimation of cadmium levels. The 114 Sn interference is stable and can be mathematically corrected. Molybdenum concentrations in urine are variable and different from individual to individual. We have estimated the degree of error which molybdenum interference introduces in the measurement of cadmium in urine by conventional ICP-MS. 268 urine samples from mothers and their children were measured. Removal of the molybdenum oxide interference (DRC-ICP-MS method) reduced urinary cadmium concentrations significantly (47.8%). The urinary molybdenum concentration in children was higher than in their mothers, resulting in greater overestimation. Our results clearly show that the DRC method is essential for reliable measurements of urinary cadmium concentrations, particularly in children. Furthermore, care should be taken when comparing Human Biomonitoring data for cadmium in urine and attention should be paid to which analytical method has been used (e.g. AAS and ICP-Ms), and especially if the measurements have been corrected for molybdenum interference.

Fast Determination of Arsenic Species and Total Arsenic in Urine by HPLC-ICP-MS: Concentration Ranges for Unexposed German Inhabitants and Clinical Case Studies

A fast and reliable high-pressure liquid chromatography (HPLC)-inductively coupled plasma-mass spectrometry (ICP-MS) routine method was developed for the determination of inorganic arsenic [As(III) and As(V)], organic monomethylarsonate [MMA(V)], dimethylarsinate [DMA(V)], and arsenobetaine (As-B) in human urine. The complete method validation is described, including internal and external quality assurance. Limits of quantification for the As species are 0.1 microg/L, which is sufficient to determine background concentrations of the arsenic species in human urine. Additionally, total As in all urine samples was determined by conventional ICP-MS. Mean concentrations for 82 non-exposed inhabitants from northern Germany are 12.7, 5.9, 4.0, 0.23, 0.52, and 0.17 microg/L for total As, As-B, DMA(V), As(III), MMA(V), and As(V), respectively. Approximately 15% of the total As was not identified by the anion exchange HPLC-ICP-MS method, and could be other As metabolites in urine. Two case studies underline the need for As speciation, especially when total urinary arsenic concentrations are elevated. In the first case, we investigated the effect of seafood consumption on the concentration of different arsenic species in urine for different persons. A maximum enhancement of total As from 1 up to 2,200 microg/L (2,000 microg/L for As-B) was observed after a normal fish meal. The second case describes the exposure of a 7-year-old child to As(III) by inhalation of calcium arsenite powder. Five hours after exposure, the concentrations in the child's urine for As-B, DMA(V), As(III), MMA(V), and As(V) were < 0.1, 189, 304, 229, and 27 microg/L, respectively, and these concentrations were reduced to normal background values after 4 days.

Study of Cell Antigens and Intracellular DNA by Identification of Element-Containing Labels and Metallointercalators Using Inductively Coupled Plasma Mass Spectrometry

The enumeration of absolute cell numbers and cell proliferation in clinical samples is important for diagnostic and research purposes. Detection of cellular DNA with fluorescent dyes is the most commonly used approach for cell enumeration in cytometry. Inductively coupled plasma mass spectrometry (ICPMS) has been recently introduced to the field of protein and cell surface antigen identification via ICPMS-linked immunoassays using element-labeled affinity reagents such as gold and lanthanide-conjugated antibodies. In the present work, we describe novel methods for using metallointercalators that irreversibly bind DNA and low concentrations of rare earth metals added to cell growth media for rapid and sensitive measurement of cell numbers by mass spectrometry. We show that Ir- and Rh-containing metallointercalators are useful reagents for labeling cells and normalizing signals when studying antigen expression on different types and numbers of cells. Results are presented for solution analysis performed by conventional ICPMS and compared to measurements obtained on the novel flow cytometer mass spectrometer (FC-MS) instrument, designed to analyze multiple antigens and DNA simultaneously in single cells.

Concentrations of selected trace elements in human milk and in infant formulas determined by magnetic sector field inductively coupled plasma-mass spectrometry.

Magnetic sector field inductively coupled plasma-mass spectrometry (ICP-MS) was applied to the reliable determination of the 8 essential trace elements cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), selenium (Se), and vanadium (V) as well as the 7 nonessential and toxic elements silver (Ag), aluminum (Al), arsenic (As), gold (Au), platinum (Pt), scandium (Sc), and titanum (Ti) in 27 transitory and mature human milk samples and in 4 selected infant formulas. This advanced instrumentation can separate spectral overlaps from the analyte signal hampering significantly the determination of many trace elements by conventional ICP-MS. Moreover, superior detection limits in the picogram per liter range can be obtained with such magnetic sector field instruments. Therefore, this is the first study to report, the concentrations of the elements Ag, Au, Pt, Sc, Ti, and V in human milk and in infant formulas. Concentrations of Ag (median: 0.41 microg/L; range: < 0.13-42 microg/L) and Au (median: 0.29 microg/L; range 0.10-2.06 microg/L) showed large variations in human milk that might be associated with dental fillings and jewelry. Pt concentrations were very low with most of the samples below the method detection limit of 0.01 microg/L. Human milk concentrations of Co (median: 0.19 microg/L), Fe (380 microg/L), Mn (6.3 microg/L), Ni (0.79 microg/L), and Se (17 microg/L) were at the low end of the corresponding reference ranges. Concentrations of Cr (24.3 microg/L) in human milk were five times higher than the high end of the reference range. For Al (67 microg/L), As (6.7 microg/L), and V (0.18 microg/L), most of the samples had concentrations well within the reference ranges. All elemental concentrations in infant formulas (except for Cr) were approximately one order of magnitude higher than in human milk.

Determination of (ultra)trace amounts of arsenic(III) and arsenic(V) in water by inductively coupled plasma mass spectrometry coupled with flow injection on-line sorption preconcentration and separation in a knotted reactor.

A method has been developed for determination of (ultra)trace amounts of As(III) and As(V) in water by flow injection on-line sorption preconcentration and separation coupled with inductively coupled plasma mass spectrometry (ICPMS) using a knotted reactor (KR). The determination of As(III) was achieved by selective formation of the As(III)-pyrrolidine dithiocarbamate complex over a sample acidity range of 0.01-0.7 mol L-1 HNO3, its adsorption onto the inner walls of the KR made from 150-cm-long, 0.5-mm-i.d. PTFE tubing, elution with 1 mol L-1 HNO3, and detection by ICPMS. Total inorganic arsenic was determined after prereduction of As(V) to As(III) in a 1% (m/v) L-cysteine-0.03 mol L-1 HNO3 media. The concentration of As(V) was calculated by difference (the total inorganic arsenic and As(III)). Owing to the group-specific character of the chelating agent, and the use of an efficient rinsing step before elution, the interferences encountered in conventional ICPMS from common major matrix, alkali and alkaline earth metals, and chlorides were eliminated. The presence of organoarsenic species such as monomethylarsonate and dimethylarsinate in water samples had no effect on the results of As(III) and As(V). Thus, the method can be applied to the speciation analysis of inorganic arsenic at submicrogram per liter levels in aqueous solutions with high total content of dissolved solid and/or high content of chlorides. Using a preconcentration time of 60 s and a sample flow rate of 5 mL min-1, an enhancement factor of 22 was achieved in comparison with conventional ICPMS. The time required for a single determination was 200 s. The detection limits (3s) was evaluated to be 0.021 microgram L-1 for As(III) and 0.029 microgram L-1 for total inorganic arsenic. The precision for 14 replicate determinations of 1 microgram L-1 As(III) was 2.8% (RSD) with drift correction and 3.9% (RSD) without drift correction. The concentrations of As(III) and As(V) in synthetic mixtures obtained by the present method were in good agreement with expected values. Results obtained by the proposed method for total arsenic in a river water reference material agreed well with certified and recently reevaluated values. The method was also applied to the speciation analysis of inorganic arsenic in porewaters.

Recycling nebulization system with a disposable spray chamber for analysis of sub-milligram samples of geological materials using inductively coupled plasma mass spectrometry

A recycling nebulization system with a disposable spray chamber was developed and evaluated for inductively coupled plasma mass spectrometry (ICP-MS). With the recycling nebulization system, 0.5 g of sample solution is sufficient for 8 min of data acquisition. The sensitivity of the recycling nebulization system was similar to a conventional Scott spray chamber system. Twenty-six trace elements were determined by ICP-MS using four internal standards (Ge, In, Re and Bi) to correct for matrix effects, instrumental drift and enrichment of the sample solution by evaporation. The ability to analyse mineral separates weighing less than 0.1 mg is demonstrated with detection limits similar to conventional procedures. Analyses of selected geological reference materials: Canada Centre for Energy and Mineral Technology (CANMET) SY-2 Syenite Rock, United States Geological Survey (USGS) reference material BCR-1 and W-1 and Centre de Recherches Petrographiques et Geochimiques (CRPG) reference material BR indicate good limits of detection, good accuracy and precision, a very low memory effect and low consumption of sample solution. Results compare well with data reported using conventional ICP-MS analysis. Analysis of the USGS geological reference material, PCC-1, for 14 rare earth elements, at ultra-trace concentration levels using cation-exchange preconcentration, is demonstrated, with limits of detection for solids of from 0.01 to 1 ng g–1 and relative standard deviations of less than 15%.