Inductively Coupled Plasma Mass Spectrometry Analysis Research Articles

Oxidative stress and mitochondrial injury-mediated cytotoxicity induced by silver nanoparticles in human A549 and HepG2 cells.

Considering the increasing applications of silver nanoparticles (AgNPs) in food- and cosmetic-related products worldwide, the aim of this study was to investigate the potential adverse health effects induced by AgNPs exposure in terms of cytotoxicity, oxidative stress, and mitochondrial injury in human A549 and HepG2 cells. After a 48 h AgNPs treatment, the cell viability was measured by MTT assay. Oxidative damage was determined by assays of malondialdehyde (MDA), 8-epi-PGF2α and 8-hydroxy-2'-deoxyguanosine (8-oxo-dG). The protein expression of HSPA1A and HO-1 was analyzed by western blot analysis. Mitochondrial membrane potential (MMP) was detected by using JC-1 as fluorescent probes. The uptake and intracellular localization of AgNPs was measured by transmission electron microscopy (TEM), and cellular AgNPs was determined by inductively coupled plasma mass spectrometry (ICP-MS). A dose-dependent decrease in cell viability after AgNPs treatment was observed, which was associated correspondingly with oxidative damage as indicated by increases in MDA amount, 8-epi-PGF2α and 8-oxo-dG levels, HSPA1A and HO-1 expression, as well as mitochondrial injury as indicated by decreased MMP. The cellular uptake of AgNPs measured by ICP-MS analysis was correlated correspondingly with the oxidative damage and mitochondrial injury. The dose-dependent cytotoxicity induced by AgNPs may result from an interaction of oxidative stress, DNA damage and mitochondrial injury in A549 and HepG2 cells. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1691-1699, 2016.

Arsenic Speciation in Honeysuckle (Lonicera japonica Thunb.) from China.

In this study, honeysuckle, a common Chinese herbal medicine, produced from different areas was investigated for total arsenic and arsenic species concentration. The total arsenic concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS) and ranged from 275 to 635μgkg(-1). A microwave-assisted procedure with 1% phosphoric acid (v/v) was used for the extraction of arsenic species in honeysuckle. The total arsenic species concentration found by liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) was in agreement with the total arsenic concentration determined by the ICP-MS analysis after the microwave digestion. Arsenate (As(V)) with an average proportion of 54.3% was the predominant arsenic species in honeysuckle. The order of concentration is as follows: As(V) > arsenite (As(III)) > dimethylarsinic acid (DMA) > arsenobetaine (AsB) > monomethylarsonic acid (MMA). The proportion of organic arsenic (24.7%) was higher than that in most terrestrial plants. Moreover, the distributions of arsenic species in the honeysuckle from different producing areas were significantly different. This study provides useful information for better understanding of the distribution of arsenic species in terrestrial plants.

A nonradioactive approach to investigate the metabolism of therapeutic peptides by tagging with 127i and using inductively-coupled plasma mass spectrometry analysis.

The metabolic fate of adrenocorticotropic hormone (ACTH) fragment 4-10 (4-10) was evaluated following incorporation of a nonradioactive (127)I-tag and with selective detection of I(+) at m/z 127 by inductively coupled plasma mass spectrometry (ICP-MS). (127)I has all the advantages of radioactive (125)I as a metabolite tracer and, together with its detection in the femtogram range, has led to a successful metabolite profiling of (127)I-ACTH (4-10) in vitro. The observed metabolic stability of this peptide in tissue preparations from human was plasma > kidney S9 > liver microsomes > liver cytosol, liver S9. Metabolic turnover of (127)I-ACTH (4-10) was not NADPH-dependent and, together with inhibition by protease inhibitor cocktail and EDTA, is consistent with metabolism exclusively by proteases. Our preliminary studies using chemical inhibitors suggested the involvement of metalloprotease, serine peptidase, and aminopeptidase in (127)I-ACTH (4-10) metabolism. The liver is the primary site of metabolic clearance of (127)I-ACTH (4-10), with kidney S9 taking four times longer to produce a metabolite profile comparable to that produced by liver S9. A total of six metabolites retaining the (127)I-tag was detected by ICP-MS, and their structures were elucidated using a LTQ/Orbitrap. (127)I-ACTH (4-10) underwent both N- and C-terminal proteolysis to produce (127)I-Phe as the major metabolite. The (127)I-tag had minimal effect on the metabolic turnover and site of proteolysis of ACTH (4-10), which, together with ICP-MS providing essentially equimolar responses, suggests that the use of a (127)I-tag may have general utility as an alternative to radioiodination to investigate the metabolism of peptide therapeutics.

Determination of picomolar beryllium levels in seawater with inductively coupled plasma mass spectrometry following silica-gel preconcentration

A robust and rapid method for the determination of natural levels of beryllium (Be) in seawater was developed to facilitate mapping Be concentrations in the ocean. A solid-phase extraction method using a silica gel column was applied for preconcentration and purification of Be in seawater prior to determination of Be concentrations with inductively coupled plasma mass spectrometry (ICP-MS). Be was quantitatively adsorbed onto silica gel from solutions with pH values ranging from 6.3 to 9, including natural seawater. The chelating agent ethylenediamine tetraacetic acid was used to remove other ions in the seawater matrix (Na, Mg, and Ca) that interfere with the ICP-MS analysis. The reproducibility of the method was 3% based on triplicate analyses of natural seawater samples, and the detection limit was 0.4pmolkg−1 for 250mL of seawater, which is sufficient for the analysis of seawater in the open ocean. The method was then used to determine the vertical profile of Be in the eastern North Pacific Ocean, which was found to be a recycled-type profile in which the Be concentration increased with depth from the surface (7.2pmolkg−1 at <200m) to deep water (29.2pmolkg−1 from 3500m to the bottom).

Determination of trace element silver in animal serum, tissues and organs by microwave digestion-ICP-MS

Nowadays, the silver is widely used in the biological field and its biological safety catches great attention. It is important to know the distribution of silver ions within the biological organism and the toxic threshold concentration in the tissue. Therefore, a highly sensitive method for measurement of trace amount of silver ion in the medical biological samples is needed. With its high sensitivity for detection of metal ions, inductively coupled plasma mass spectrometry (ICP-MS) method is well suited for quantification of trace amount of silver ion in such samples, but method development is still in its infancy. Consequently, a simple and convenient method for determination of trace amount of silver in the animal serum, tissues or organs was developed, in which the samples were subjected to the microwave digestion, followed by the ICP-MS analysis. To begin with, the samples of serum, muscle, bone marrow, bone, heart, liver, spleen, and kidney were sequently processed in 5 mL of HNO3 and 2 mL of H2O2 solution. Then the samples were completely digested by microwave with the power of 2 000 watts. The temperature was raised gradually by 3-step program. Moreover, the data achieved were reproducible and the method was time saving and especially for large amounts of sample processing. Then the digested solutions were diluted to constant volume. Finally, the concentration of 107Ag in the samples was analyzed by the method of ICP-MS under the optimized conditions. Element yttrium (Y) was used as the internal standard to compensate for matrix suppression effect and improve the accuracy of measurement. For one thing, the analytical results showed that the detection limit of the trace element 107Ag was 0.98 μg · kg(-1), and furthermore, the correlation coefficient of standard curve was 0.999 9. For another thing, the recovery rate of the silver element ranged from 98% to 107%, which was calculated according to measured quantity before adding standard, adding standard and measured quantity after adding standard. At the same time, the relative standard deviation (RSD) of the method was in the range of 2.0%-4.3%. The concentrations of element silver in animal serum, tissues and organs were determined by the aboved method. The obtained results showed that silver ions were mainly accumulated in the liver after they were intaken into the body. The results suggested that the microwave digestion-ICP-MS method could accurately determine the trace element Ag in the body. The method developed has good feasibility and is suitable for the determination of trace element Ag in various types of medical and biological samples, especially for large quantities of biological samples. The process has the advantages of easysample processing and it is simple and convenient. In addition, the accurate results could be obtained in a short time with high sensitivity. Last but not least, the method provides the guidance for the determination of trace elements in other biological samples.

Controls on quartzite bearing base-metal sulfide and invisible gold mineralization at Gabal Abu Houdied area, South Eastern Desert, Egypt

The Neoproterozoic basement rocks cropping out in the Gabal Abu Houdied (GAH) area comprises mainly three lithotectonic assemblages; mafic–ultramafic ophiolitic rocks, island arc-related metasediment–metavolcanic rocks and syn- and post-tectonic intrusions. The base-metal sulfide and invisible gold mineralization are restricted to quartzites, which are considered as member of island arc-related metasediment rocks. The mineralized quartzite rocks are cropped out at three localities, at Wadi El Haussioum where cover a small area (0.25 km2), at Bir Abu Houdeid, cover small area (0.5 km2), and at Bir Shani (3.5 km long with different width ranging from 4 to 75 m). Based on textural characteristics and chemical features, documented by electron probe microanalysis (EPMA) and inductively coupled plasma mass spectrometry analyses (ICP-MS), two phases of sulfide minerals assemblages in the investigated quartzites of GAH area. An early mineralization phase includes pyrite, pyrrhotite, argentite (acanthite) and invisible gold, and the late phase, dominated by pyrite, galena, sphalerite, chalcopyrite, covelite, and ± invisible gold. Analyses of the structural data collected from the quartzite rocks and surroundings indicated that the base-metal sulfide and associated gold mineralization in the GAH area are mostly controlled by D3 transperssional deformation event. This event is main Hamisana shear zone (HSZ) deformation event and characterized by transperssional stress regime, with σ1 trending E–W and σ3 trending N–S governed conjugate NNW sinistral and NNE–SSW dextral strike slip faulting.

Arsenate adsorption onto hematite nanoparticles under alkaline conditions: effects of aging

Arsenate adsorption onto freshly synthesized hematite nanoparticles was carried out under highly alkaline conditions (~pH 10) at room temperature (21 °C). Dynamic light scattering measurements of hydrated hematite colloids ranged from 43 to 106 nm (~96 %). The measured zeta potential was 28.1 mV (±5.85) suggesting that the hematite nanoparticles were moderately stable. X-ray diffraction and Raman spectroscopy data showed that hematite was stable under the conditions tested, with no crystal modification evident at the completion of the experiment (9 days). An additional band position at ~826 cm−1 in the Raman spectra represented arsenate adsorbed onto hematite. The pH of the slurry dropped from ~10 to ~8 during the experiment; this was coincident with a drop in the aqueous concentration of arsenic (from ~121 to ~92 mg/L) as determined via inductively coupled plasma mass spectrometry (ICP-MS). ICP-MS analyses on the solid samples indicated a significant amount of arsenic partitioned to the solid phase during aging, corroborating the results of aqueous analyses. X-ray absorption spectroscopic analyses revealed that the bonding environment remained the same irrespective of the pH and the amount of arsenate adsorbed. Arsenate adsorbed onto hematite through a strong inner-sphere bidentate-mononuclear complex both before (0 days) and after (9 days) aging. These results are valuable for understanding the fate of potential contaminants in alkaline mine tailings environments where 2-line ferrihydrite frequently transforms to hematite rather than goethite.

Determination of Boron in Coal Using Closed-Vessel Microwave Digestion and Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

Boron in coal is of great interest, mainly because it can be used as paleosalinity indicator; it is also of environmental concern because of its toxic effects, especially on land plants. This paper describes a new method for determination of the boron concentration in coal by inductively coupled plasma mass spectrometry (ICP-MS) after closed-vessel microwave digestion. Samples of raw coal rather than coal ash were used for the determination to avoid the loss of volatile organically bound boron. Addition of H3PO4 to the HNO3 and HF used as reagents in the process could also significantly diminish boron volatilization during acid-drying after sample digestion. A 2% ammonia solution, which was injected into an ICP-MS spray chamber to eliminate the memory effect of boron, may reduce boron signals to blank levels (within 120 s) during ICP-MS analysis. The boron concentrations of National Institute of Standards and Technology (NIST) standard reference coal samples obtained using the ICP-MS in high-resolution mode and with 103Rh or 115In used as online addition internal standards are in good agreement with the certified values.

Analysis of bioaccessible concentration of trace elements in plant based edible materials by INAA and ICPMS methods

The total metal concentration and bioaccessible concentration of Cr, Mn, Fe, Cu, Zn, Se in Momordica charantia, Asparagus racemosus, Terminalia arjuna and Syzyzium cumini were measured by instrumental neutron activation analysis and by inductively coupled plasma mass spectrometry analysis (ICP-MS). The bioaccessible concentrations were determined in the gastrointestinal digest obtained after treating dried powdered samples sequentially in gastric and intestinal fluid of porcine origin at physiological conditions. The bioaccessible concentration of Fe was in the range of 58–67 mg kg−1, Mn was 10.2–14.6 mg kg−1, Cu was 3.7–4.8 mg kg−1 and Zn was 10.6–18.4 mg kg−1, were within the safety limits set for vegetable food stuff set by Joint FAO/WHO. The bioaccessibility of Zn, an essential element, was high (40–50 %) in M. charantia and in S. cumini. In addition, the total metal contents and bioaccessible concentration of Ni, Se, Cd and Pb in these samples were measured by ICP-MS. The total Cd content in S. cumini (2.6 ± 0.2 mg kg−1) and its bioaccessible concentration (0.6 mg kg−1) were strikingly high as compared to the other samples. Though total Hg contents were determined by ICP-MS, but their bioaccessible concentrations were below the detection limit (0.036 mg kg−1).

Multi-stage growth and invisible gold distribution in pyrite from the Kundarkocha sediment-hosted gold deposit, eastern India

Gold mineralization at Kundarkocha, India, is hosted in sheared gray quartz veins that were emplaced in carbonaceous pyritic phyllite. Gold occurs as enclosed grains within sulfides and free grains in quartz. Based on characteristic textural and chemical features, documented by X-ray element imaging, electron probe microanalysis and laser-ablation inductively-coupled plasma mass spectrometry analyses, four pyrite types were identified in carbonaceous phyllites and auriferous veins. Rock-hosted fine-grained syn-sedimentary to early diagenetic pyrite framboids (PyI) have lower contents of Co and As but consistently high gold values. Pyrite of the next generation (PyII) has numerous silicate and rare sulfide inclusions; lower contents of Co and Ni, moderate As values; the highest mean value of invisible gold and maximum concentrations of trace elements such as Li, Ti, Zn, Rb, Sr, Y, Zr, Nb, La, Ce, Ta, Th, U and Cr. Pyrite of the third generation (PyIII) shows evidence of overgrowth over PyII, contains both silicate and sulfide inclusions, and are characterized by moderate contents of Co, high Ni and low Au values and higher concentrations of large ion lithophile elements, but lesser amount of high field strength elements. Pyrites of the latest type (PyIV) occur as polycrystalline aggregates that contain inclusions of gold, sulfides and rare silicates, show oscillatory zoning of Co and As and the lowest concentrations of all other trace elements. Successive decrease in contents of majority of trace elements from PyII to PyIV is attributed to fluid-assisted recrystallization during diagenesis and low grade metamorphism.Later generation pyrites (PyII through PyIV) exhibit higher Au contents regardless of their As values, indicating occurrence of invisible gold mostly as nanoparticles, at times reaching up to 500ppm. Unlike the majority of trace elements that underwent large-scale remobilizations, gold was somehow locked up in pyrite resulting in a rather lean deposit at Kundarkocha.

The study of in vivo acute effect of two different delivery modalities of iron oxide core with titanium dioxide shell nanoparticles in rabbits liver tumor.

e22204 Background: To compare intravenous (IV) versus fluoroscopy-guided transarterial intra-catheter (IC) delivery of iron oxide core with titanium dioxide shell nanoparticles (NPs) in vivo in VX2 model of liver cancer in rabbits and detect the NPs distribution and effect of NPs presence on the target tumor and other rabbit’s organs. Methods: After obtaining the IACUC approval, liver tumors were obtained by implantation of tumor tissue obtained from a hind limb VX2 tumor of donor rabbits. NPs were delivered either IV or IC. After rabbit termination, 2 hours post NPs injection, tumor, liver, kidney, lung and spleen were harvested, split in half and a part of it was frozen while the remainder was formalin fixed and paraffin embedded. To assess the NPs distribution in 2D we stained 5um thick paraffin tissue sections using Dopamine-Biotin-DHS histochemical (HC) staining followed by Nanozoomer microscopy analysis. H and E staining, TUNEL assay and Ki67 immunohistochemistry were also done. X-ray Fluorescence Microscopy (XFM) was used to quantify the NPs. Frozen tissue was used for bulk NPs concentration analysis using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results: This study included ten rabbits; 3 rabbits had IV NPs injections, 3 had IC NPs injection, 2 control and 2 donors. ICP-MS analysis showed statistically significant higher NPs concentration in tumors of IC arm vs. IV arm (p= 0.0356), while there was higher concentration of NPs in liver (p=0.00077) and spleen (p = 0.01356) of IV vs. IC arms but no difference in kidneys or lungs. These findings were consistent with results from HC and XFM analyses. HC 2D analysis of NPs distribution showed that the RES have taken up the NPs non-specifically. There were no statistically significant differences between the treatment groups regarding the Ki67 proliferation or the TUNEL apoptosis indices or when control rabbits were compared to NPs treated rabbits. Conclusions: Both IV and IC NPs injection are feasible modalities for delivering NPs to tumors with acceptable acute systemic effects and comparable tumor effect. IV delivery increased sequestration of the NPs by RES and their accumulation in spleen and liver.

The use of solution nebulization ICP-MS combined with particle screening and micro-sampling for analysis of individual uranium-bearing particles

Solution nebulization inductively coupled plasma mass spectrometry (ICP-MS) was applied to the analysis of uranium isotope abundance ratios in individual particles. Particle screening was carried out before ICP-MS analysis using two different techniques: irradiation with thermal neutrons and fission track observation (so-called “fission track technique”) on the one hand and automated particle measurement (APM) in secondary ion mass spectrometry (SIMS) on the other hand. Uranium-bearing particles localized by the screening techniques were sampled individually by micro-sampling devices inside a scanning electron microscope and deposited on clean silicon wafers for subsequent chemical dissolution and ICP-MS measurement. The micro-sampling enables us to avoid polyatomic ion interferences and measure some uranium-bearing particles at the same time in isotopic analysis. Using both methods, particles from certified reference materials and a real-life sample taken at a nuclear facility were measured to evaluate the performance of the methods. Using ICP-MS combined with the fission track technique, the uranium isotope abundance ratios were successfully determined for individual particles with diameters ranging from 1.2 to 2.4 μm in a certified reference material (NBL CRM U100). The analysis of the real-life sample using ICP-MS combined with the fission track technique gave 235U/238U isotope abundance ratios between 0.0246 and 0.0376. When APM was used as the particle screening method for the real-life sample, 235U/238U isotope abundance ratios ranging from 0.0259 to 0.0432 were obtained. These values were higher than those obtained by a well-established method for particle analysis (SIMS). From these results, it can be concluded that both techniques allow selection and analysis of the uranium particles with the highest 235U abundance, which is the most important for nuclear safeguards.

MeCAT – comparing relative quantification of alpha lactalbumin using both molecular and elemental mass spectrometry

Chemical tagging with stable isotopes is one of the best established methods for the quantification of proteins using mass spectrometry, especially in non-proliferating cells and tissue. The absolute quantification of proteins is still a challenge. Metal-coded affinity tagging (MeCAT), used to label proteins and peptides with lanthanide ions, allows both, relative and absolute, quantitative determination. MeCAT loaded with lanthanide ions allows the use of inductively coupled plasma mass spectrometry (ICP-MS) enabling very accurate and sensitive quantification of peptides and proteins based on the metal ion signal. Furthermore, multiplex assays are possible that are not limited to 4- or 8-plex analyses when using different lanthanides. Naturally, different lanthanides also lead to different molecular masses for the same labelled peptides which can be distinguished easily. This enables the relative quantification in electrospray MS based on the relative signal intensities of the differentially labelled peptides. We have studied MeCAT labelled peptides, using LC/ESI-MS and LC/ESI-MS/MS with infrared multiphoton dissociation (IRMPD) to show that both the molecular masses and the specific fragments resulting from the MS/MS experiments can be used for relative quantification. The results are compared with high performance liquid chromatography (HPLC)/ICP-MS and direct ICP-MS analysis as standard methods. We show that the ESI and IRMPD based methods deliver quantitative results comparable to ICP-MS.

Concentrations of Platinum Group Elements (Pt, Pd, Rh) in Airborne Particulate Matter (PM2.5and PM10-2.5) Collected at Selected Canadian Urban Sites: a Case Study

Increasing environmental concentrations of platinum group elements (PGEs), in particular platinum (Pt), palladium (Pd) and rhodium (Rh), from catalytic converters has been reported worldwide. Initially it was believed that the emitted PGEs remain in the roadside environment, but recent studies have shown that fine PGE-containing particles can be transported and distributed at regional and long-range levels. Therefore, the monitoring of PGEs in airborne particulate matter (PM) is important for the estimation of potential risks to human health and to the ecosystem. The aim of this study is to present the first results from an analysis on the concentration and distribution of Pt, Pd and Rh in PM collected on Teflon filters at two selected urban sites (Toronto, Ontario; Edmonton, Alberta) collected within the Canadian National Air Pollution Surveillance (NAPS) network. In this work, a quadruple inductively coupled plasma mass spectrometry (ICP-MS), combined with microwave assisted acid digestion using aqua regia was used. A cation exchange separation was used to alleviate the matrix-induced spectral and nonspectral interferences prior to ICP-MS analysis. To obtain sufficient material needed for PGEs analysis, fine PM (particles with aerodynamic diameter less than 2.5 mm; PM2.5 ) and coarse PM (with aerodynamic diameter between 2.5 and 10 mm; PM10-2.5 ) samples were combined into composite samples on a seasonal basis. The obtained results will be discussed and compared with literature data.

Toxic and essential elements in conventional and home-produced eggs by ICP-MS analysis

Concentrations of As, Ba, Cd, Co, Mn, Pb, Se, Sr, V, Cu, Fe, Mg, Zn and Mo were determined in conventional and home-produced eggs as sold in Brazil. Thirty-four conventional and 21 home-produced samples were obtained in different Brazilian cities. Elements were determined by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of Ba, Cd, Co, Pb, Se, Fe, Zn and Mo in conventional and home-produced eggs differed (statistically significant). Correlations were found among the other elements in both production systems. The estimated daily intake for toxic elements based on Brazilian egg consumption did not exceed the toxicological reference values. The results clearly demonstrated that eggs are an important source of essential elements such as Mo, Fe, Se and Zn.

Immunochromatographic assay of cadmium levels in oysters

Oysters are one of foodstuffs containing a relatively high amount of cadmium. Here we report on establishment of an immunochromatographic assay (ICA) method of cadmium levels in oysters. Cadmium was extracted with 0.lmolL−1 HCl from oysters and cleaned up from other metals by the use of an anion-exchange column. The behavior of five metals Mn, Fe, Cu, Zn, and Cd was monitored at each step of extraction and clean-up procedure for the ICA method in an inductively coupled plasma-mass spectrometry (ICP-MS) analysis. The results revealed that a simple extraction method with the HCl solution was efficient enough to extract almost all of cadmium from oysters. Clean-up with an anion-exchange column presented almost no loss of cadmium adsorbed on the column and an efficient removal of metals other than cadmium. When a spiked recovery test was performed in the ICA method, the recovery ranged from 98% to 112% with relative standard deviations between 5.9% and 9.2%. The measured values of cadmium in various oyster samples in the ICA method were favorably correlated with those in ICP-MS analysis (r2=0.97). Overall results indicate that the ICA method established in the present study is an adequate and reliable detection method for cadmium levels in oysters.

Particle characterisation in chemical looping combustion

In a chemical looping combustion process, as the oxygen carrier circulates the system, it is subjected to morphological and compositional changes such as sintering, attrition and reaction between metal oxides and fuels. These changes may cause the deactivation of the oxygen carrier to decrease over time. This research work is carried out to investigate and characterise the iron oxide and copper oxide particles used in a chemical looping combustion system after 20 reduction–oxidation cycles with 5 different fuels, (i.e. Hambach lignite coal, Hambach lignite char, activated carbon, Taldinski bituminous coal and US bituminous coal). Oxygen carriers used in this study were subjected to analyses with X-ray diffraction (XRD), inductive coupled plasma mass spectrometry (ICP-MS), scanning electron microscope (SEM) and BET surface area and full isotherm analysis. XRD analysis on these particles showed that the reduced particles were reoxidised back to their original form with trace amounts of impurities such as silicon dioxide (SiO 2) on the iron oxide particles whereas similar impurities plus copper complexes such as copper aluminate were detected on the copper oxide particles. ICP-MS analysis on these particles revealed that the concentration of the core metal elements (iron, copper and alumina) decreased after 20 reaction cycles which in turn decreased the total concentration of the metal elements in the particles. BET surface area analysis on these particles indicated that the total surface area of these particles decreased by more than 50% of their original values. Full isotherm analysis on the copper oxide particles showed that the total pore volume of the particles decreased after 20 reaction cycles even though the pore sizes of the particles increased slightly. SEM analyses showed the iron oxide particles underwent severe attrition whereas the copper oxide particles showed signs of agglomeration due to the high operating temperature.

Development of a discriminatory biocompatibility testing model for non-precious dental casting alloys

Objectives To develop an enhanced, reproducible and discriminatory biocompatibility testing model for non-precious dental casting alloys, prepared to a clinically relevant surface finishing condition, using TR146 oral keratinocyte cells. Methods Comparative biocompatibility was determined following direct and indirect exposure of TR146 cells to two nickel–chromium (Ni–Cr) and a cobalt–chromium (Co–Cr) alloy-discs. The surface roughness of the discs was determined using a contact stylus profilometer and the elemental ion release by inductively coupled plasma mass spectrometry (ICP-MS). Subsequent biocompatibility analysis included cell morphology, cell density measurements with Trypan blue exclusion assay, inflammatory cytokine expression with ELISAs, cellular metabolic activity using XTT and cellular toxicity using lactate dehydrogenase (LDH) release assay. Results TR146 cell morphology was altered following direct and indirect exposure to the Ni–Cr alloys but not the Co–Cr alloy. Significant reductions (all P < 0.001) in viable cell density measurements, cellular metabolic activity, significant increases inflammatory cytokine expression and cellular toxicity were observed when TR146 cells were exposed to the Ni–Cr alloys. Significant decreases in cell density measurements, cellular metabolic activity, significant increases inflammatory cytokine expression and cellular toxicity for the Ni–Cr d.Sign ®15 alloy compared with d.Sign ®10 alloy were identifiable (all P < 0.001). Cellular toxicity was attributed to nickel ion release levels in solution detected by ICP-MS analysis. Discussion Nickel ions from the Ni–Cr alloys permeated the epithelial cells and activated a proinflammatory response, namely IL-1a, IL-8 and PGE2 expression. Further evidence of nickel ioninduced cell death was supported by the decreased biocompatibility of the highest nickel ion releasing alloy (d.Sign ®15 compared with d.Sign ®10) and the increased biocompatibility of the Co–Cr (d.Sign ®30) alloy where nickel ions were absent.

Experimental investigation of the effects of mineral dust on the reproducibility and accuracy of ice core trace element analyses

Determination of trace element concentrations by inductively coupled plasma mass spectrometry (ICP-MS) can yield valuable information about paleoclimate from ice core records. Typically, ICP-MS analyses are performed on melted and acidified ice core samples which contain particulate material i.e., mineral dust. This particulate material is usually enriched in trace elements relative to ice core samples. Consequently, it is important to constrain the effect of acidification on mineral dust present in ice core samples and to assess the contribution of dust leaching to the trace element budget of ice cores. We have conducted a systematic experimental investigation designed to replicate the conditions of conventional ice core trace element analyses. Powdered rock standards of various lithologies were leached in 1 wt.% HNO 3 and the leachates were sampled at regular time intervals. Oxides and sheet silicate minerals, in the ferromanganese nodule (Nod-P-1) and granite (JG-2) leachates respectively, released available trace elements into solution relatively quickly; trace element recovery reached 57% for Mg and 42% for Mn in the granite leachate and recoveries between 60 and 80% were reached for most elements in the ferromanganese nodule leachate after only 12 h of leaching. In contrast, mafic minerals in the basalt (BHVO-2) and dolerite (W-2) released trace elements slowly, achieving recoveries of < 20% for elements from Li to Mn after 12 h of leaching. The mafic minerals continued to release trace elements into solution over several weeks causing Al and Ti concentration increases to > 4000%. These results demonstrate that acidification of ice core samples containing mineral dust will cause time- and mineral-dependent leaching of trace elements. Leaching behaviour of trace elements remained constant with varying mineral dust concentration but freezing pre-acidified samples was found to promote leaching of some trace elements. Ideally, all ice core samples would be fully digested or filtered to eliminate the error introduced by partial dissolution of dust but this is time-consuming and impractical. We therefore recommend acidifying samples for as long as practical to reach a maximum leachable concentration. For datasets obtained by conventional methods, Al is identified as the most suitable element to use as a terrestrial tracer because it is leached to a uniform extent across all lithologies. Fundamental flaws are identified in the calculation of crustal enrichment factors which are likely to cause some elements to appear enriched as a result of incongruent leaching. Ratios of trace elements, in particular rare earth elements (REEs), leached from mineral dust will not reflect those of the dust and are not suitable as tracers of dust provenance.

Challenges and successes in using inductively coupled plasma mass spectrometry for measurements of tungsten in environmental water and soil samples

Military small arms ranges in the United States have been used for munitions training with tungsten rounds, which are comprised of powdered tungsten (W) pressed together with polymeric binders. As a result, W has been introduced into surface soils. The environmental and human health effects of W remain open questions. The US Army Corps of Engineers is responsible for environmental monitoring, site assessments, and cleanup of small arms ranges. This work requires routine measurements of tungsten in natural waters and soils. However, the existing sample preparation and analytical procedures were not specifically developed with W in mind for environmental analysis. Our work suggests modification of existing metal sample preparation and analytical procedures are necessary to accurately quantify W in environmental media. Our group has been actively conducting W measurements using inductively coupled plasma mass spectrometry (ICPMS), both with quadrupole and sector field ICPMS systems. We have used heavy rare earth elements and iridium as internal standards. For soils, the great majority of the W from small arms can be dissolved using acid leaching with HNO3–H3PO4 mixtures; more rigorous preparations with fusion or HF digestions can also be used. In ICPMS analysis, the largest challenge involves dealing with the significant carry-over and memory of W in sample introduction systems. This ultimately limits measurement capabilities, particularly at sub-µg L−1 levels. With careful attention to the sample and standards’ matrix constituents, and proper washout time, successful analysis is possible and ICPMS is clearly the preferred technique. A commercially available fluoropolymer sample introduction system exhibits significantly improved memory characteristics.