Isotope Dilution ICP-MS Research Articles

Dissolved platinum in rainwater, river water and seawater around Tokyo Bay and Otsuchi Bay in Japan

Platinum, among the rarest elements in the earth's crust, is now widely used in various products such as catalytic converters in automobiles and anticancer drugs. Consequently, the concentration of Pt in urban aquatic environments might be increasing. However, little is known about the distributions and geochemical cycles of Pt in aquatic environments because its overall concentration remains low. In this study, we examined dissolved Pt in river water and seawater around Tokyo Bay and Otsuchi Bay (Iwate Prefecture, Japan) and rainwater in the Tokyo area. To determine sub-picomolar levels of dissolved Pt, we used isotope-dilution Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after column preconcentration with an anion exchange resin. We observed seasonal variation in the dissolved Pt concentrations in Tokyo rainwater in 2002; higher concentrations were found from January to March, which might be related to the pH of rainwaters. At the source of the Arakawa River in the greater Tokyo area, the dissolved Pt concentration was found to be similar to that in rainwater. Further downstream, the dissolved Pt concentration increased sharply, which seemingly reflects the anthropogenic input of Pt into the river. In a rural area in Japan (Otsuchi Bay), the dissolved Pt concentrations were lower than in Tokyo Bay. In this area, a sharp increase in dissolved Pt concentrations was observed in a high salinity region. Contrasting Pt distribution patterns between urban and rural areas indicate that strong anthropogenic Pt sources exist in urban estuaries and that geochemical processes within estuaries affect the Pt distribution.

Assay methods for 238U, 232Th, and 210Pb in lead and calibration of 210Bi bremsstrahlung emission from lead

Assay methods for measuring 238U, 232Th, and 210Pb concentrations in refined lead are presented. The 238U and 232Th concentrations are determined using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) after anion exchange column separation of dissolved lead samples. The 210Pb concentration is inferred through {\alpha}-spectroscopy of a daughter isotope, 210Po, after chemical precipitation separation on dissolved lead samples. Subsequent to the 210Po {\alpha}-spectroscopy assay, a method for evaluating 210Pb concentrations in solid lead samples was developed via measurement of bremsstrahlung radiation from \b{eta}-decay of a daughter isotope, 210Bi, by employing a 14-crystal array of high purity germanium (HPGe) detectors. Ten sources of refined lead were assayed. The 238U concentrations were <34 microBq/kg and the 232Th concentrations ranged <0.6-15 microBq/kg, as determined by the ICP-MS assay method. The 210Pb concentrations ranged from ~0.1-75 Bq/kg, as inferred by the 210Po {\alpha}-spectroscopy assay method.

Accurate quantification of selenoproteins in human plasma/serum by isotope dilution ICP-MS: focus on selenoprotein P

Systematic approach for the accurate quantification of selenoproteins (SEPP1) in human plasma/serum by IDA-LC-ICP-MS.

Distribution of neptunium and plutonium in New Mexico lichen samples (Usnea arizonica) contaminated by atmospheric fallout

The concentrations of 237Np, 239Pu and 240Pu were determined in lichen samples (Usnea arizonica) that were collected from ten locations in New Mexico between 2011 and 2013 using isotope dilution inductively-coupled plasma mass spectrometry (ID-ICP-MS). The observed isotopic ratios for 237Np/239Pu and 240Pu/239Pu indicate trace contamination from global and regional fallout (e.g. Trinity test and atmospheric testing at the Nevada Test Site). The fact that actinide contamination is detected in recent lichen collections suggests continuous re-suspension of fallout radionuclides even 50 years after ratification of the Limited Test Ban Treaty.

Speciation of cisplatin in environmental water samples by hydrophilic interaction liquid chromatography coupled to inductively coupled plasma mass spectrometry

Cisplatin is still widely used for treatment of numerous types of tumours. Different speciation methods have been applied to study behaviour of the intact drug and its individual biotransformation species in various clinical samples. These methods are mainly based on electrophoresis, size exclusion (SEC) or ion chromatography (IC) techniques coupled to inductively coupled plasma mass spectrometry (ICP–MS). Hydrophilic interaction liquid chromatography (HILIC), which is a common technique for separation of polar substances, was rarely applied for separation of cisplatin and its hydrolysed metabolites. There is also a lack of information available on the occurrence of cisplatin and its hydrolysed complexes in the environmental waters. In the present study the concentrations of Pt were determined in hospital wastewaters by ICP–MS. A procedure for separation of cisplatin and its aqueous hydrolysed complexes by the use of HILIC column was optimized. Quantification of separated Pt species was performed by isotope dilution (ID)–ICP–MS procedure. Low limits of detection (LODs) and quantification (LOQs) were obtained for cisplatin and its hydrolysed complexes ranging from 0.0273 to 0.1726ngPt/mL and from 0.0909 to 0.5753ngPt/mL, respectively. Good repeatability of the procedure with relative standard deviation (RSD) lower than ±2.3% was obtained. The column recoveries, which ranged from 95 to 101%, indicated that the procedure developed enabled quantitative speciation analysis of aqueous cisplatin complexes. The ZIC-HILIC–ID–ICP–MS procedure was successfully applied in speciation of cisplatin in spiked hospital wastewater samples.

Report of the key comparison CCQM-K108 determination of arsenic species, total arsenic and cadmium in brown rice flour

The CCQM-K108 key comparison was organised by the Inorganic Analysis Working Group(IAWG) of CCQM to test the abilities of national metrology institutes (NMIs) or designated institutes (DIs) to measure the mass fractions of arsenic species, total arsenic and cadmium in brown rice flour. The National Metrology Institute of Japan (NMIJ) acted as the coordinating laboratory. The participants used different measurement methods, though most of them used inductively coupled plasma mass spectrometry (ICP-MS) or isotope-dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) for Cd and ICP-MS for total arsenic. Regarding arsenic speciation, all participants used ICP-MS coupled with liquid chromatography (LC). Accounting for relative expanded uncertainty, comparability of measurement results for each of total arsenic and cadmium was successfully demonstrated by the participating NMIs or DIs for the measurement of the measurand at the level of less than 0.5 mg/kg. Regarding arsenic species (inorganic arsenic and dimethylarsinic acid (DMAA)), there was, however, a measurement problem still to be solved and that part of CCQM-K108 will be repeated.It is expected that arsenic, cadmium and other metals at mass fractions greater than approximately 0.1 mg/kg in rice flour can be determined by each participant using the same technique(s) employed for this key comparison to achieve similar uncertainties mentioned in the present report. Furthermore, the results of this key comparison can be utilised along with the IAWG core capability approach.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A simple procedure to select a model for mass discrimination correction in isotope dilution inductively coupled plasma mass spectrometry

A fast, simple and straightforward procedure to decide on the best model to calculate the mass discrimination factor in Isotope Dilution Inductively Coupled Plasma Mass Spectrometry (ID-ICP-MS) is proposed.

New method for the speciation of ruthenium-based chemotherapeutics in human serum by conjoint liquid chromatography on affinity and anion-exchange monolithic disks

An important step in pharmacological characterisation of a candidate drug is the study of the drugs interactions with serum proteins. In the present work, conjoint liquid chromatography (CLC) was used for separation of ruthenium (Ru)-based drug candidates in human serum. CIM Protein G and CIM DEAE disks were assembled together in a single housing forming a CLC monolithic column. By applying isocratic elution with Tris–HCl–NaHCO3 buffer (pH 7.4) in the first min, followed by gradient elution with 1molL−1 NH4Cl (pH 7.4) in the next 9min, immunoglobulins (IgG) were retained by the Protein G disk enabling subsequent separation of unbound Ru species from Ru species bound to human serum transferrin (Tf) and albumin (HSA) on the CIM DEAE disk. Finally, elution with acetic acid (AcOH) in the next 3min allowed separation of Ru species associated with IgG. Protein elution was followed on-line with UV detection at 278nm, while the separated Ru species were quantified by post-column isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). The instrumental set-up enabled fast two-dimensional separation by affinity and ion-exchange modes to be carried out in a single chromatographic run. Two Ru-based chemotherapeutics: a newly synthesised compound chlorido(η6-p-cymene)(nalidixicato-κ2O,O)Ru(II) (1) and (H2im)[trans-Ru(III)Cl4(Him)2] (2; KP418), which is currently undergoing preclinical studies, were investigated. The CLC procedure applied is sensitive with low limit of detection (LOD) (0.027μgRumL−1 for (1)) and good method repeatability (RSD±3.5%). The experimental data revealed that it enables investigation of the kinetics of interaction of positively charged and neutral complexes of metallodrugs with serum proteins as well as the distribution of metallodrug species in human serum. However, negatively charged metallic complexes co-eluted with Tf and HSA and thus hindered their speciation analysis. An example of successful application of the kinetic studies on the CLC column is (1), a neutral Ru complex that hydrolyses to a positively charged species. For comparison, speciation data obtained for serum samples spiked with cisplatin are also shown.

Comparison of sample digestion techniques for the determination of trace and residual catalyst metal content in single-wall carbon nanotubes by inductively coupled plasma mass spectrometry

A single-wall carbon nanotube material produced by laser ablation of renewable biochar in the presence of Ni and Co catalyst was characterized for residual catalyst (Co and Ni) as well as trace metal impurity content (Fe, Mo, Cr, Pb and Hg) by isotope dilution ICP-MS following sample digestion. Several matrix destruction procedures were evaluated, including a multi-step microwave-assisted acid digestion, dry ashing at 450°C and microwave-induced combustion with oxygen. Results were benchmarked against those derived from neutron activation analysis and also supported by solid sampling continuum source GF-AAS for several of the elements. Although laborious to execute, the multi-step microwave-assisted acid digestion proved to be most reliable for recovery of the majority of the analytes, although content of Cr remained biased low for each approach, likely due to its presence as refractory carbide.

Precise determination of dissolved platinum in seawater of the Japan Sea, Sea of Okhotsk and western North Pacific Ocean

Platinum is among the least abundant elements in the earth's crust and is now widely used in various products such as catalytic converters in automobiles and anticancer drugs. Consequently, the concentration of Pt in urban aquatic environments is increasing. However, little is known about the distributions and geochemical cycles of Pt in the ocean owing to its low concentrations in seawater (<0.2pmol/L). In this study, we report an improved analytical method for determining sub-picomolar levels of Pt in seawater, and reveal the distributions of Pt in the Japan Sea, Sea of Okhotsk, and western North Pacific Ocean.For determining sub-picomolar levels of Pt in seawater, we used isotope-dilution ICP-MS (Inductively Coupled Plasma Mass Spectrometry) after column preconcentration with an anion exchange resin. This method facilitated highly accurate analysis of Pt in seawater using small sample volumes (~1L). The detection limit and procedural blank value for this method were 0.015 and approximately 0.01pmol/L, respectively. We obtained conservative vertical distributions, with nearly constant Pt concentrations between 0.19 and 0.25pmol/L in the Japan Sea, Sea of Okhotsk, and western North Pacific Ocean. Judging from the constant dissolved Pt profiles, little anthropogenic influence of Pt is apparent in the open oceans at the present time.

The composition of dissolved iron in the dusty surface ocean: An exploration using size-fractionated iron-binding ligands

Abstract The size partitioning of dissolved iron and organic iron-binding ligands into soluble and colloidal phases was investigated in the upper 150 m of two stations along the GA03 U.S. GEOTRACES North Atlantic transect. The size fractionation was completed using cross-flow filtration methods, followed by analysis by isotope dilution inductively-coupled plasma mass spectrometry (ID-ICP-MS) for iron and competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) for iron-binding ligands. On average, 80% of the 0.1–0.65 nM dissolved iron ( 99% of dissolved iron in the ocean is organically complexed. Disentangling the chemical form of iron in the upper ocean has important implications for surface ocean biogeochemistry and may affect iron uptake by phytoplankton.

A method for determination of PGE–Re concentrations and Os isotopic compositions in environmental materials

Automobile catalyst emissions not only result in increasing environmental concentrations of Pt, Pd, and Rh, but also Os, Ir, and Ru. Little is known about the behavior of platinum-group elements (PGE) and Re in the environment and their potential risk to humans and, as such, the monitoring of Os, Ir, Ru, and Re concentrations in environmental samples is necessary. We present an improved procedure for determination of PGE-Re concentrations and Os-187/Os-188 ratios of the environmental reference material BCR-723 by isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) and negative thermal ionization mass spectrometry (N-TIMS), respectively. The sample is digested with inverse aqua regia in a Carius tube. After Os separation by CCl4 solvent extraction, separation and purification of PGE and Re from sample matrix elements is sequentially performed by a two-stage tandem column setup using cation exchange and N-benzoyl-N-phenylhydroxylamine (BPHA) extraction resin. Elution of 0.1 mol L-1 HCl efficiently removes interfering elements such as Zr, Hf, Mo, and Cd in the final purified sample prior to ID-ICP-MS determination of PGE and Re. Analyses of BCR-723 yield reproducible results and well-defined average Pt, Pd, Os, Ir, Ru, and Re concentrations of 79.8 +/- 6.0, 4.6 +/- 0.8, 0.37 +/- 0.04, 0.23 +/- 0.12, 1.1 +/- 0.3, and 6.5 +/- 0.1 ng g(-1), respectively (95% confidence level; n = 10). The Os-187/Os-188 ratio of this standard was determined to be 0.537 +/- 0.022 (95% confidence level; n = 10). These are the first comprehensive PGE and Re concentrations and Os isotopic compositions reported for BCR-723 and provide a well-characterized standard for assessing the data quality of autocatatyst PGE measurements and related research on environmental materials. The method was successfully employed in the determination of PGE and Re concentrations and Os isotopic compositions in urban road dust samples.

Accurate determination and certification of bromine in plastic by isotope dilution inductively coupled plasma mass spectrometry

The accurate analytical method of bromine (Br) in plastic was developed by an isotope dilution inductively coupled plasma mass spectrometry (ID-ICPMS). The figures of merit of microwave acid digestion procedures using polytetrafluoroethylene (PTFE) or quartz vessels were studied and the latter one was suitable for Br analysis since its material was free from Br contamination. The sample dilution procedures using Milli-Q water or ammonium (NH3) solution were also studied to remove memory effect for ICPMS measurement. Although severe memory effect was observed on Milli-Q water dilution, NH3 solution could remove it successfully. The accuracy of the ID-ICPMS was validated by a certified reference material (CRM) as well as the comparison with the analytical result obtained by an instrumental neutron activation analysis (INAA) as different analytical method. From these results, the ID-ICPMS developed in the present study could be evaluated as accurate analytical method of Br in plastic materials and it could apply to certification of Br in candidate plastic CRM with respect to such regulations related to RoHS (restriction of the use of hazardous substances in electrical and electronics equipment) directive.

Precise determination of dissolved silica in seawater by ion-exclusion chromatography isotope dilution inductively coupled plasma mass spectrometry

Ion exclusion chromatograph (IEC) isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP–MS) (IEC–ID–ICP–MS) was developed for measurement of dissolved silica in seawater, which was applied to production of certified reference materials (CRMs) of three concentration levels of nutrients (high, medium and low levels). IEC–ICP–MS has been employed to separate dissolved silica from seawater matrix. In the present study, in order to solve substantial problems due to spectral interference in ICP–MS and to improve the accuracy of IEC–ICP–MS beyond standard addition or conventional calibration methods, ID method was coupled with ICP-sector field mass spectrometry (operated under medium resolution,i.e., m/Δm=4000). In addition, effects of various operating parameters in ICP–MS on a silicon background level were also investigated to obtain lower background equivalent concentration (BEC). As a result, 3ngg−1 of the BEC and 0.5 % of relative standard uncertainties were achieved in the analyses of dissolved silica in seawater samples at concentration levels from 4.0 mg kg -1 to 0.8mgkg−1 as silicon. The developed method was successfully validated by analyses of an artificial seawater containing a known amount of silicate and the seawater certified reference material MOOS-2 produced by the National Research Council Canada.

Precise determination of seawater calcium using isotope dilution inductively coupled plasma mass spectrometry

We describe a method for rapid, precise and accurate determination of calcium ion (Ca(2+)) concentration in seawater using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). A 10 μL aliquot of seawater was spiked with an appropriate (43)Ca enriched solution for (44)Ca/(43)Ca ID-ICP-MS analyses, using an Element XR (Thermo Fisher Scientific), operated at low resolution in E-scan acquisition mode. A standard-sample bracketing technique was applied to correct for potential mass discrimination and ratio drift at every 5 samples. A precision of better than 0.05% for within-run and 0.10% for duplicate measurements of the IAPSO seawater standard was achieved using 10 μL solutions with a measuring time less than 3 minutes. Depth profiles of seawater samples collected from the Arctic Ocean basin were processed and compared with results obtained by the classic ethylene glycol tetra-acetic acid (EGTA) titration. Our new ID-ICP-MS data agreed closely with the conventional EGTA data, with the latter consistently displaying 1.5% excess Ca(2+) values, possibly due to a contribution of interference from Mg(2+) and Sr(2+) in the EGTA titration. The newly obtained Sr/Ca profiles reveal sensitive water mass mixing in the upper oceanic column to reflect ice melting in the Arctic region. This novel technique provides a tool for seawater Ca(2+) determination with small sample size, high throughput, excellent internal precision and external reproducibility.

Evidence of Increased Anthropogenic Emissions of Platinum in Coastal Systems from Time-Series Analysis of Mussels Samples (1991-2011)

Evidence of Increased Anthropogenic Emissions of Platinum in Coastal Systems from Time-Series Analysis of Mussels Samples (1991-2011)

Determination of total mercury in biological tissue by isotope dilution ICPMS after UV photochemical vapor generation

A method is developed for the determination of trace mercury in biological samples using photo chemical vapor generation (PVG) and isotope dilution inductively coupled plasma mass spectrometry (ID ICPMS) detection. Biological tissues were solubilized in formic acid. Subsequently, the sample solutions were exposed to an ultraviolet (UV) source for the reduction of mercury into vapor species prior to ICPMS measurements. The formic acid served not only as a tissue solubilizer in the sample preparation procedure, but also as a photochemical reductant for mercury in the PVG process. The problem arising from the opaque formic acid digested solution was efficiently solved by using ID method. The optimum conditions for sample treatment and PVG were investigated. A limit of detection (LOD) of 0.5 pg g(-1), based on an external calibration, provided 350-fold improvement over that obtained by utilizing conventional pneumatic nebulization sample introduction. Method validation was demonstrated by the determination of total mercury in several biological tissue certified reference materials (CRMs). The results were in good agreement with the certified values.

Distribution and behaviour during metasomatism of PGE–Re and Os isotopes in off-craton mantle xenoliths from Namibia

Platinum-group element (PGE) and Re–Os isotopes were measured by isotope dilution ICPMS in five well-characterised peridotite xenoliths from the Gibeon kimberlite field in the Proterozoic Rehoboth Terrane, Namibia. The distribution of these elements and Os isotopes between different size and mineral fractions within the samples indicates that incompatible Pd and Pt likely reside in minerals typically <1mm size, such as interstitial sulphides of magmatic–metasomatic origin, whereas compatible Ir and Os may be controlled by primary–residual sulphide inclusions in large silicates. The lowest Pd/Ir, which decreases during partial melting and increases during melt metasomatism, and the most depleted (least radiogenic) 187Os/188Os (0.1112–0.1190) are consistently obtained for opx-rich fractions in cpx-poor samples, which therefore represent the most promising targets to date melt extraction from the mantle. Significant Os isotope disequilibrium between fractions containing opx and secondary cpx in the same sample implies that non-modal partial melting of such rocks could generate melts with 187Os/188Os different from their average source mantle. Like Lu–Hf, but unlike Sm–Nd, PGE concentrations and Os isotopes appear to be transparent to cryptic metasomatism by carbonate melts or fluids, as evidenced by preservation of the least radiogenic Os and low Pd/Ir in the sample with the most unradiogenic (enriched) Nd and radiogenic (depleted) Hf. In contrast, both modal metasomatism (clinopyroxene addition) at 0.45Ga and silicate melt metasomatism at 1.85Ga led to higher Pd/Ir and direct addition of radiogenic Os and/or Re addition followed by ingrowth of radiogenic Os, with 187Os/188Os up to 0.179. Although the mantle beneath the Rehoboth Terrane, which adjoins the Kaapvaal craton, has features resembling Archaean lithospheric mantle (e.g., cool conductive geothermal gradient, occasional opx enrichment), only one aliquot in one of the fractions measured in this study yielded a Re-depletion age consistent with Archaean melt extraction (2.71±0.08Ga). Given uncertainties regarding the Os isotope composition and heterogeneity of the convecting mantle source from which the lithospheric mantle is ultimately derived, evidence for an — albeit probable — Archaean provenance remains inconclusive.

Isotope dilution inductively coupled plasma mass spectrometry for determination of 126Sn content in spent nuclear fuel sample

The 126Sn content in a spent nuclear fuel solution was determined by isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) for its inventory estimation in high-level radioactive waste. A well-characterized irradiated UO2 fuel sample dissolved in a hot cell was used as a sample to evaluate the reliability of the methodology. Prior to the ICP-MS measurement, Sn was separated from Te (126Te), which causes major isobaric interference in the determination of 126Sn content, along with highly radioactive coexisting elements, such as Sr (90Sr), Y (90Y), Cs (137Cs) and Ba (137m Ba), using an anion-exchange column. The absence of counts attributed to Te at m/z = 125, 128, and 130 in the Sn-containing effluent (Sn fraction) indicates that Te was completely removed from the anion-exchange column. After washing, Sn retained on the column was readily eluted with 1 M HNO3 accompanied with approximately 80% of the Cd and 0.03% of the U in the initial sample. Owing to the presences of Cd and U in Sn fraction, the measurements of 116Sn and 119Sn were affected by the isobaric 116Cd and the doubly charged 238U2+ion, resulting in the positive bias of the determined values. With the exception of the isotopic ratios including 116Sn and 119Sn, 117Sn/126Sn, 118Sn/126Sn, 120Sn/126Sn, 122Sn/126Sn and 124Sn/126Sn were successfully determined and showed good agreement with those obtained through ORIGEN2 calculations. The measured concentration of 126Sn in the spent nuclear fuel sample solution was 0.74 ± 0.14 ng/g, which corresponds to 23.0 ± 4.5 ng per gram of the irradiated UO2 fuel (excluding the presence of 126Sn in the insoluble residue). The results reported in this paper are the first experimental values of 126Sn content and isotope ratios in the spent nuclear fuel solution originating in spent nuclear fuel irradiated at a nuclear power plant in Japan.

Migration of antimony from PET trays into food simulant and food: determination of Arrhenius parameters and comparison of predicted and measured migration data

Migration experiments with small sheets cut out from ovenable PET trays were performed in two-sided contact with 3% acetic acid as food simulant at various temperatures. The fraction of diffusible antimony (Sb) was estimated to be 62% in the PET sample under study. Apparent diffusion coefficients of Sb in PET trays were determined experimentally. Measurement of migration between 20 and 150°C yielded a linear Arrhenius plot over a wide temperature range from which the activation energy (E a) of 188 ± 36 kJ mol−1 and the pre-exponential factor (D 0) of 3.6 × 1014 cm2 s−1 were determined for diffusing Sb species. E a was similar to previously reported values for PET bottles obtained with a different experimental approach. E a and D 0 were applied as model parameters in migration modelling software for predicting the Sb transfer in real food. Ready meals intended for preparation in a baking oven were heated in the PET trays under study and the actual Sb migration into the food phase was measured by isotope dilution ICP-MS. It was shown that the predictive modelling reproduces correctly experimental data.