Isotope Dilution ICP-MS Research Articles

Compensation of isotope ratio mismatch in double isotope dilution inductively coupled plasma mass spectrometry (ID-ICP/MS)

Abstract Exact-matching double isotope dilution inductively coupled plasma mass spectrometry (ID-ICP/MS) is widely used to characterize reference materials (RMs) in elemental analysis. In this technique, achieving exactly matching isotope ratios for the sample and calibration blends is regarded as an important prerequisite for obtaining accurate measurement results. However, meeting this condition requires multiple time-consuming iterative measurements. In the current study, an alternative approach that can avoid lengthy iterative procedures while maintaining the accuracy of the ID-ICP/MS results was successfully investigated. We examined the effects of an extensively wide range of inexact-matching isotope ratios (approximately 75 %–130 %) in double ID-ICP/MS for elements with a wide mass range. Our experimental study, using gravimetrically prepared samples of Ca, Cd, Cu, Fe, Hg, Mg, Ni, Pb, and Zn, demonstrated that, despite deliberately introducing mismatching of isotope ratios, the accuracy of the ID-ICP/MS results remained consistent with relative measurement bias of typically less than 0.5 %. The absence of a systematic bias due to deviations in the sample blend isotope ratios from the target ratios of the calibration blends revealed that the variability due to an isotope ratio mismatch was sufficiently compensated for. Furthermore, the expanded measurement uncertainties were sufficiently small with negligible variations observed across the different matching ratios. Typically, they were less than 1 %, except for Fe, Hg, Pb, and Zn which were less than 2 %. This assertion is also supported by theoretically calculated error magnification factors. Consequently, it is feasible to directly utilize the marginally estimated mass fraction of the analyte of interest without extensive iterative measurements. The findings of this study provide robust data for ID-ICP/MS, allowing to circumvent lengthy iterative procedures while maintaining the accuracy and precision of the measurement results, particularly in the characterization of reference materials for elemental analysis.

Uncertainty evaluation in reference material characterization by double isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS)

Double isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) is one of the most important measurement methods in the establishment of measurement standards for inorganic analysis. However, there is still no good consensus on approaches for uncertainty evaluation in double ID-ICP-MS. Particularly, approaches to treating the instrumental isotopic fractionation (IIF) phenomenon and correlation between uncertainty sources are diverse and often unclear in the literature. Here, an approach for uncertainty evaluation in double ID-ICP-MS measurements is described. Using three certified reference materials (CRMs), it is shown that the IIF effects cancel out and should not be included in the uncertainty budget. Further, a consistent way of considering correlated sources of uncertainty to prevent double counting of uncertainties is described in detail along with an example of measuring the mass fraction of magnesium in an oyster powder CRM.

Certification of visinin-like protein-1 (VILIP-1) certified reference material by amino acid-based and sulfur-based liquid chromatography isotope dilution mass spectrometry.

As an emerging neurodegenerative disease, Alzheimer's disease (AD) has become a leading cause of dementia in older adults. Visinin-like protein-1 (VILIP-1) is an increasingly used biomarker for AD besides the widely accepted Aβ1-40, Aβ1-42, and tau. However, significant variations exist in the commercial immuno-based assays for VILIP-1 quantification, underlining the necessity to establish a traceability chain. Certified reference materials (CRMs) located at the top of the traceability chain are traceability sources for relevant matrix standard materials. In this work, VILIP-1 solution CRM with a certified value and uncertainty of 39.82±1.52 μg·g-1 was developed and certified using amino acid-based isotope dilution mass spectrometry (AA-ID-MS) and sulfur-based isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). Certified values from both strategies showed great consistency, with traceability to SI units. Moreover, the candidate VILIP-1 CRM shows excellent homogeneity and can be stable for at least 7 days at -20°C and 12 months at -70°C. The VILIP-1 CRM developed can be used in value assignment to secondary calibrators and clinical matrix CRMs, showing prospects in early diagnosis and disease monitoring for AD.

Determination of the sub-picomolar concentration of dissolved palladium in open ocean seawater

Palladium, which is used in various fields, including automobile catalysis, is a precious metal with an extremely low content (0.4 μg/kg) in the earth's crust. Previous studies have suggested its release from anthropogenic sources into a wide range of environments, including aquatic environments. However, reliable analytical methods by which it can be quantified have not yet been established owing to its extremely low concentration in aquatic environments and the vulnerability of its measurements to interfering elements. Therefore, the aim of this study was to establish a highly sensitive and accurate analytical method for its quantification in open ocean seawater using isotope dilution-inductively coupled plasma mass spectrometry (ICP-MS) and thereafter, clarify its vertical distribution. To establish the analytical method, the effects of the concentrations and compositions of the cleaning solution and eluent used during the column pre-concentration process on the analysis were examined. Further, we applied the ammonia dynamic reaction cell (NH3 DRC) during ICP-MS measurements and also optimized the NH3 gas flow rate as well as rejection parameter, q (Rpq). The open ocean seawater samples were acidified to obtain 0.5 M HCl concentration followed by the addition of 105Pd isotope enriched spike solution. Thereafter, the samples were allowed to stand for 24 h before analysis. Solid-phase extraction of Pd in seawater was performed using an anion exchange resin (AG1-X8). To remove interfering elements, a cleaning method was employed. Specifically, cadmium, with the most significant effect on Pd measurements, was removed using HNO3 (> 0.5 M), while other interfering species, including strontium and zirconium were removed using either HCl or HNO3. The flow rate of the cleaning solution and the eluate were also optimized. Thus, a pre-concentration method with a Pd recovery rate of 89–95% was established. Furthermore, the isobaric interference caused by 90Zr16O+, which increased the procedural blank value of our analytical method and could not be completely removed during pre-concentration, was eliminated by employing NH3 DRC in the ICP-MS process, while that caused by 88Sr14N1H3+ was suppressed by setting the NH3 gas flow rate above 1.8 mL/min and the Rpq at 0.81. Thus, when 470 mL of open ocean seawater samples were analyzed under these conditions, the detection limit and blank value obtained were 0.060 and 0.050 pmol/L, respectively (both of which are lower than previously reported values). Additionally, an investigation of the vertical distribution of Pd in the North Pacific using the established methods revealed that Pd concentrations showed a tendency to decreased from 0.32 pmol/L at depth of 50 m to 0.10 pmol/L at a depth of 1500 m, and at depths below 2000 m, the concentrations varied in the range 0.10–0.13 pmol/L. Therefore, our established method showed sufficient suitability for the determination of the sub-picomolar concentration of Pd in open ocean seawater.

New matrix certified reference materials for the measurement of trace elements in swine and chicken compound feed

New animal feed matrix certified reference materials (CRMs) were developed to measure Cu, Fe, Mn, and Zn trace elements in swine and chicken compound feed. The market-obtained raw feed materials were ground, blended, homogenized, bottled, and gamma-irradiated to prepare the CRM candidates. We then employed isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), flame atomic absorption spectroscopy (FAAS), and inductively coupled plasma mass spectrometry (ICP-MS) as reference methods in collaborative characterization program. The certified values and expanded uncertainties (at a confidence level of 95%, k = 2) of Cu, Fe, Mn, and Zn were assigned to be 60.48 ± 1.84, 367.0 ± 14.7, 159.1 ± 6.8, and 335.2 ± 7.7 μg/g in the swine compound feed CRM, respectively, and 39.53 ± 3.08, 332.0 ± 19.9, 111.3 ± 10.4, and 132.1 ± 7.8 μg/g in the chicken compound feed CRM, respectively. The homogeneity, short-term stability at 60˚C for 9 days, long-term stability at − 20˚C and room temperature for 18 months, and uncertainty evaluation were sufficiently studied. Thus, these two CRMs can be used for quality control and method validation to ensure the accurate and reliable measurements of swine and chicken feed for quality and safety monitoring.

High-Accuracy Determination of Potassium and Selenium in Human Serum by Two-Step Isotope Dilution ICPMS.

A high-accuracy measurement technique for determining potassium and selenium in human serum was developed by using two-step Isotope Dilution Inductively Coupled Plasma-Mass Spectrometry (ICPMS) in this research. A more accessible method of the quadrupole ICPMS was employed in this research to achieve an equally high accuracy which had been achieved by a much more expensive method, namely, high-resolution sector field ICPMS (SF-ICPMS), with a comparatively easy and simple operation. In addition, we have evaluated the uncertainty of this method. The results showed that the determination limits of potassium and selenium in serum were 0.8 mg/kg and 2.7 μg/kg, respectively, and the precision for both measurements was lower than 0.2% and 0.7%. The measurement, when employed to measure potassium and selenium in standard materials NIST956D, NIST909C, and GBW09152, had caused a maximum deviation of less than 0.9%, within the stated uncertainty range of standard materials. The RELA international inter-laboratory comparisons of potassium in serum in 2018 conducted by our laboratory also yielded a satisfactory result.

Species-specific isotope dilution analysis of monomethylmercury in sediment using GC/ICP-ToF-MS and comparison with ICP-Q-MS and ICP-SF-MS

A recently introduced inductively coupled plasma-time-of-flight-mass spectrometer (ICP-ToF-MS) shows enhanced sensitivity compared to previous developments and superior isotope ratio precision compared to other ToF and commonly used single-collector ICP-MS instruments. Following this fact, an improvement for isotope dilution ICP-MS using the new instrumentation has been reported. This study aimed at investigating whether this improvement also meets the requirements of species-specific isotope dilution using GC/ICP-MS, where short transient signals are recorded. The results of the analysis of monomethylmercury (MMHg) of a sediment reference material show that isotope ratio precision of ICP-MS instruments equipped with quadrupole, sector-field, and time-of-flight mass analyzers is similar within a broad range of peak signal-to-noise ratio when analyzing one isotopic system. The procedural limit of quantification (LOQ) for MMHg, expressed as mass fraction of Hg being present as MMHg, w(Hg)MMHg, was similar as well for all investigated instruments and ranged between 0.003 and 0.016 μg/kg. Due to the simultaneous detection capability, the ICP-ToF-MS might, however, be more favorable when several isotopic systems are analyzed within one measurement. In a case study, the GC/ICP-ToF-MS coupling was applied for analysis of MMHg in sediments of Finow Canal, a historic German canal heavily polluted with mercury. Mass fractions between 0.180 and 41 μg/kg (w(Hg)MMHg) for MMHg, and 0.056 and 126 mg/kg (w(Hg)total) for total mercury were found in sediment samples taken from the canal upstream and downstream of a former chemical plant.Graphical abstract

CONTROLS ON THE METAL ENDOWMENT OF PORPHYRY Mo DEPOSITS: INSIGHTS FROM THE LUMING PORPHYRY Mo DEPOSIT, NORTHEASTERN CHINA

AbstractProcesses controlling the metal endowment of arc-related porphyry Mo deposits are not well understood. Located in northeastern China, the arc-related Luming porphyry Mo deposit has a proven reserve of 0.75 Mt Mo at an average grade of 0.092 wt % and is characterized by multiple pulses of alteration and mineralization. These features make this deposit an ideal location to investigate the role of multiple pulses of magmatism and fluid release in the evolution and formation of an arc-related porphyry Mo deposit. Molybdenum mineralization at Luming is typically observed as a series of molybdenite-bearing veins hosted within a composite intrusive complex, referred to as the Luming Intrusive Suite. Crosscutting relationships between intrusive units and offset veins indicate that the Luming Intrusive Suite is composed of five major, successive granitic intrusions: the premineralization plutonic biotite monzogranite and monzogranite units, and the synmineralization stock- and dike-like porphyritic monzogranite, granite porphyry, and syenogranite units. Each synmineralization unit is associated with similar vein sequences that comply with the general form of early EB-type biotite veins, through A-type quartz ± biotite and B-type quartz-molybdenite veins, to late D-type quartz-molybdenite ± pyrite ± chalcopyrite, molybdenite, quartz-pyrite ± calcite, and calcite ± clays veins. The intensity and volume of alteration and mineralization within a given synmineralization unit decrease from early- through inter- to late-mineralization units. Although minor Mo mineralization is associated with potassic alteration along B-type veins, the majority of the ore is associated with D-type quartz-molybdenite-pyrite and molybdenite veins rimmed by sericite-chlorite-pyrite alteration, which are primarily hosted in the two premineralization units.A combination of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U-Pb and hydrothermal biotite 40Ar/39Ar studies, together with available isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS) molybdenite Re-Os data, has resulted in a substantial reappraisal of the timing of magmatism and its association with molybdenite mineralization at Luming. The volumetrically dominant premineralization intrusive units have indistinguishable zircon U-Pb weighted mean 206Pb/238U ages ranging from 187.5 ± 2.8 to 186.5 ± 3.6 Ma (2σ), whereas the synmineralization units yield weighted mean 206Pb/238U ages from 178.6 ± 2.2 to 175.6 ± 3.0 Ma (2σ). The zircon U-Pb weighted mean 206Pb/238U ages of the synmineralization units are indistinguishable from the mean molybdenite Re-Os model (178.1 ± 2.7; 2σ) and hydrothermal biotite 40Ar/39Ar plateau (174.7 ± 1.1 Ma; 2σ) ages within uncertainty, confirming a genetic link with mineralization. Melt inclusion data show that the synmineralization intrusions were Mo poor, with Mo concentrations <4 ppm.The data presented here suggest that molybdenite mineralization at Luming was most likely accomplished through three discrete magmatic-hydrothermal events during assembly of the Mo-poor synmineralization intrusive complex. The giant Luming deposit appears to be related to multiple pulses of magmatic-hydrothermal activities, resulting in the superposition of temporally distinct mineralization events. Our results suggest that pulsed release of ore-forming magmas and fluids, which are channeled along focusing structures like small porphyry fingers within a focused area, from a large magma chamber at depth may play a major role in the formation of large to giant porphyry Mo deposits of both the arc-related and Climax types. This conclusion is in line with field observations of a number of large to giant porphyry Mo deposits, which commonly show reversals in magmatic-hydrothermal evolutionary trend and are associated with multiple pulses of small stocks and dikes that are separate in time and space.

Budgets and sources of dissolved platinum in the inland seas of Japan

Platinum (Pt) is used in a variety of industrial and medical applications, including automobile catalysis and anticancer drugs. At present, anthropogenic Pt is released and dispersed in the environment globally. Previously reported, vertical profiles of dissolved Pt in coastal seawaters indicated an increase in the Pt concentrations from the surface to the bottom, suggesting that Pt in seawater may be supplied from seafloor sediments, although this benthic supply process remains unresolved. Therefore, in this study, we sought to reveal the geochemical cycles of Pt between the seawater and sediments in inland seas, such as Japan's Ariake Sea, which is a semi-enclosed sea, thus allowing the examination of the interactions between seawater, river water, and sediments. Seawater and sediment samples were collected from this sea and the nearby Tachibana Bay. The former was analyzed for relevant hydrographic properties (temperature, salinity, and dissolved oxygen) along with Pt concentration, while the latter underwent fractional dissolution to determine dissolved Pt using isotope-dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) after column preconcentration with an anion exchange resin. The observed Pt concentrations in seawater ranged from 0.41 to 10.2 pmol/L with the highest value occurring at the deepest layer of the Ariake Sea's mouth. The Pt concentrations increased with depth, with decreasing concentrations toward the inner central Ariake Sea. Detectable Pt contents in the sediment were found in the exchangeable, Fe and Mn oxide, and residual phases. Loosely adsorbed Pt onto the sediment might be desorbed by interactions with chloride in seawater. A model for the Pt budget in the Ariake Sea estimated that most Pt was supplied from sediments, and the Pt residence time was longer than that of seawater.

Binding Kinetics of Ruthenium Pyrithione Chemotherapeutic Candidates to Human Serum Proteins Studied by HPLC-ICP-MS.

The development of ruthenium-based complexes for cancer treatment requires a variety of pharmacological studies, one of them being a drug’s binding kinetics to serum proteins. In this work, speciation analysis was used to study kinetics of ruthenium-based drug candidates with human serum proteins. Two ruthenium (Ru) complexes, namely [(η6-p-cymene)Ru(1-hydroxypyridine-2(1H)-thionato)Cl] (1) and [(η6-p-cymene)Ru(1-hydroxypyridine-2(1H)-thionato)pta]PF6 (2) (where pta = 1,3,5-triaza-7-phosphaadamantane), were selected. Before a kinetics study, their stability in relevant media was confirmed by nuclear magnetic resonance (NMR). Conjoint liquid chromatography (CLC) monolithic column, assembling convective interaction media (CIM) protein G and diethylamino (DEAE) disks, was used for separation of unbound Ru species from those bound to human serum transferrin (Tf), albumin (HSA) and immunoglobulins G (IgG). Eluted proteins were monitored by UV spectrometry (278 nm), while Ru species were quantified by post-column isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). Binding kinetics of chlorido (1) and pta complex (2) to serum proteins was followed from 5 min up to 48 h after incubation with human serum. Both Ru complexes interacted mainly with HSA. Complex (1) exhibited faster and more extensive interaction with HSA than complex (2). The equilibrium concentration for complex (1) was obtained 6 h after incubation, when about 70% of compound was bound to HSA, 5% was associated with IgG, whereas 25% remained unbound. In contrast, the rate of interaction of complex (2) with HSA was much slower and less extensive and the equilibrium concentration was obtained 24 h after incubation, when about 50% of complex (2) was bound to HSA and 50% remained unbound.

Provision of primary NIST traceability to support vapor phase mercury emissions monitoring of combustion sources using isotope dilution inductively coupled plasma mass spectrometry

Primary mercury gas standards, traceable to the SI, have been developed which can be used to underpin a NIST traceability framework for the calibration of vapor phase continuous emission monitoring systems (CEMS). A gas standard, which is based on a commercial gas generator, has been certified for gaseous elemental mercury output at specified generator output set points. The standard, termed the NIST Prime (NP) was certified at selected set points in the range 0.25 μg/m3 to 38 μg/m3 by isotope dilution inductively coupled plasma – mass spectrometry (ID-ICP-MS) using two alternative approaches, based on directly coupled gas sampling, and activated carbon sorbent trapping. Both approaches have been used to provide NIST traceability for electric utility mercury CEMS. The directly coupled method yielded expanded measurement uncertainties ranging from approximately 5.5% relative at 0.5 μg/m3, to approximately 1% relative at 38 μg/m3, and an estimated limit of quantitation (LOQ) of 0.06 μg/m3. The sorbent trapping method in contrast, yielded expanded uncertainties of approximately 1% relative at all sampling points, with an LOQ of 0.001 μg/m3.

Isotope dilution inductively coupled plasma mass spectrometry to measure the bioaccessible fraction of chromium in sediments

The bioaccessible fraction of chromium in marine sediments is determined first time using isotope dilution Inductively Coupled Plasma Mass Spectrometry (ID-ICPMS). A diluted hydrochloric acid solution enriched with 53Cr was used as extractant to achieve isotope equilibration with the mass fraction of Cr extracted, using ultrasonic probe agitation. The parameters affecting trueness and precision were evaluated and/or corrected to minimize the errors; namely: detector dead time, spectral interferences, mass discrimination factor and selection of the optimum sample/spike ratio. The fraction of Cr measured correlated well with the sum of the certified contents of the 3-step sequential extraction of the Standards, Measurements and Testing Programme, SM&T, when analysing the BCR-701 sediment. The method provided good reproducibility (1.4% RSD) and low detection limit, 16.7 ng g−1. Three additional reference sediments with certified total chromium contents were also analysed as quality control checks. The total uncertainty budget of the procedure was estimated following the EURACHEM Guide propagating together the individual uncertainty components of the isotope dilution, obtaining a satisfactory relative expanded uncertainty of 1.9%. The analysis of sediments from two rias of Galicia (Arousa and Vigo, Northwest Spain) demonstrated the applicability of the proposed methodology.

Determination of ultra-trace sulfur in high-purity metals by isotope dilution inductively coupled plasma sector field mass spectrometry combined with chemical separation procedure

The analytical method of ultra-trace sulfur (S) in high-purity metal by isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) combined with chemical separation procedure was developed in the present study. In order to determine the ultra-trace S in high-purity metal, a chemical separation with alumina column was carried out before ICP-MS measurement. This method enabled to prevent the polyatomic ion interference arising from the metal matrix and the signal suppression derived from the space charge effect in ICP-MS. In order to achieve high sensitive analysis, an ICP-sector field mass spectrometer (ICP-SFMS) was used. The isolation of polyatomic ion interference with respect to S was also carried out in medium-resolution mode. In addition, measurement conditions including detector dead time, which affects the precision and accuracy of the isotope dilution method, and washout conditions that were employed to reduce memory effects were optimized. The developed method was validated by the determination of S in a high-purity iron reference material (JSS-001–4). The analytical result obtained by the developed method (1.86 mg kg−1 ± 0.12 mg kg−1 (k = 2)) was in good agreement with the certified value (1.90 mg kg−1 ± 0.42 mg kg−1). The method was also applied to the determination of S in high-purity zinc, revealing a content of 0.08 mg kg−1 ± 0.08 mg kg−1 (k = 2). Since the developed method enabled the determination of ultra-trace S at μg kg−1 level in the high-purity zinc, it is expected to be useful for high sensitive and accurate determination of ultra-trace S in high-purity metals.

Determination of cadmium in sediments by diluted HCI extraction and isotope dilution ICP-MS

Isotope dilution ICP-MS is proposed to measure the mass fraction of Cd extracted by diluted HCl in marine sediments, using a fast and simple extraction procedure based on ultrasonic probe agitation. The 111Cd isotope was added before the extraction to achieve isotope equilibration with native Cd solubilized from the sample. The parameters affecting trueness and precision of isotope ratio measurements were evaluated carefully and subsequently corrected in order to minimize errors; they were: detector dead time, spectral interferences, mass discrimination factor and optimum sample/spike ratio. The mass fraction of Cd extracted was compared with the sum of the certified contents of the three steps of the sequential extraction procedure of the Standards, Measurements and Testing Programme (SM&T) analysing the BCR 701 sediment to validate the method. The certified and measured values agreed, giving a measured / certified mass fraction ratio of 1.05. Further, the extraction procedure itself was studied by adding the enriched isotope after the extraction step, which allowed verifying that analyte losses occurred during this process. Two additional reference sediments with certified total cadmium contents were also analysed. The method provided very good precision (0.9%, RSD) and a low detection limit, 1.8 ng g−1. The procedural uncertainty budget was estimated following the EURACHEM Guide by means of the ‘GUM Workbench’ software, obtaining a relative expanded uncertainty of 1.5%. The procedure was applied to determine the bioaccessible mass fraction of Cd in sediments from two environmentally and economically important areas of Galicia (rias of Arousa and Vigo, NW of Spain).

Study on the determination of ¹⁰B/¹¹B isotope ratio in water samples by isotope dilution – inductively coupled plasma mass spectrometry (ID-ICPMS)

The determination of 10B/11B isotope ratio and boron concentration in various water samples using isotope dilution technique with inductively coupled plasma mass spectrometry (ICPMS) was studied. The interferences on precision and accuracy in isotopic ratio determination by ICPMS such as memory effects, dead time, spectral overlap of 12C were investigated for the selection of optimum conditions. By the addition of certain amounts of enriched 10B into samples, the 10B/11B ratio was determined through ICP-MS signal of 10B and 11B. The detection limit for 10B and 11B was experimentally obtained as 0.26 µg/L and 0.92 µg/L, respectively. The ratios of 10B/11B in measured water samples varied in the ranged between 0.1905 and 0.2484 for different matrices. This method has been then applied for the determination of boron isotopic ratio in VVER-1000 reactor-type simulated primary coolant water and in some environmental water samples.

Development of certified reference materials for electrolytes in human serum (GBW09124-09126).

Three reference materials, at relatively low, middle, and high concentrations, were developed for analysis of the mass fractions of electrolytes (K, Ca, Na, Mg, Cl, and Li) in human serum. The reference materials were prepared by adding high purity chloride salts to normal human serum. The concentration range of the three levels is within ±20% of normal human serum. It was shown that 14 units with duplicate analysis is enough to demonstrate the homogeneity of these candidate reference materials. The statistical results also showed no significant trends in both short-term stability test for 1week at 40°C and long-term stability test for 14months. The certification methods of the six elements include isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), atomic absorption spectroscopy (AAS), ion chromatography (IC), and ion-selective electrode (ISE). The certification methods were validated by international comparisons among a number of national metrology institutes (NMIs). The combined relative standard uncertainties of the property values were estimated by considering the uncertainties of the analytical methods, homogeneity, and stability. The range of the expanded uncertainties of all the elements is from 2.2% to 3.9%. The certified reference materials (CRMs) are primarily intended for use in the calibration and validation of procedures in clinical analysis for the determination of electrolytes in human serum or plasma. Graphical Abstract Certified reference materials for K, Ca, Mg, Na, Cl and Li in human serum (GBW09124-09126).

Nickel speciation in cocoa infusions using monolithic chromatography - Post-column ID-ICP-MS and Q-TOF-MS.

Nickel (Ni) is considered to be a potentially harmful element for humans. Its levels in foodstuffs are normally low (below 0.2mgkg-1), but sensitive individuals may develop allergy to Ni as a result of dietary consumption. Cocoa contains relatively high Ni concentrations (around 3mgkg-1). Ni bioavailability, its role in the flavour of food and its potential impact on human health depends primarily on its chemical species. However, there is a lack of information about Ni speciation in cocoa. In this work Ni species were separated on a weak convective interaction media diethylamine (CIM DEAE) monolithic chromatographic column and quantified by the post-column isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). The Ni binding ligands in the separated fractions were identified "off line" by quadrupole time-of-flight mass spectrometry (Q-TOF MS). Ni was found to be present in the cocoa infusions as Ni2+ and Ni-gluconate and Ni-citrate complexes.

LGC-1: A zircon reference material for in-situ (U-Th)/He dating

A pairwise in-situ (U-Th)/He dating method has been proposed for mitigating matrix-related bias in U and Th measurements using synthetic reference materials. This method requires a natural zircon reference material whose (U-Th)/He age should be homogeneous on the scale (~10–100μm) to be used in such dating experiments. A newly characterized zircon LGC-1 megacryst fulfils this requirement. This pale-yellowish, flawless Sri Lanka gem specimen is about 1.2∗0.8∗0.8cm in size. Optical microscopy, cathodoluminescence-imaging, X-ray elemental mapping, and Raman spectroscopy on a large number of random shards did not reveal any detectable textural and compositional heterogeneity. Laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) analyses on a large number of randomly selected fragments yield 266 measurements of U, Th and Pb concentrations, which are within the corresponding experimental uncertainties. The weighted mean U, Th and Pb concentrations are 357.7±1.8ppm, 740.9±5.0ppm, and 39.06±0.18ppm, respectively, with a weighted mean Th/U ratio of 2.07±0.01, indistinguishable from Isotope Dilution ICP-MS (ID-ICP-MS) and Thermal Ionization Mass Spectrometry (ID-TIMS) results. ID-TIMS U/Pb ages are concordant within uncertainties of decay constants, with a concordia age of 541.70±0.70Ma. Conventional (U-Th)/He dating on 28 random shards from the crystal in different laboratories gives a central age of 476.4±5.7Ma. Six in-situ (U-Th)/He analyses yield consistent 4He concentrations and ages with weighted mean values of 1248±46nmol/g and 462±21Ma, respectively. Fractions of this zircon have been shared with several laboratories in the Australia, China, UK and US, and are expected to serve as a reference for both in-situ and conventional (U-Th)/He analyses. The combination of analytical methods used to characterize LGC-1 zircon may be used as a template for future age reference calibration.

Final report on CCQM-K125: elements in infant formula

CCQM-K125 was organized by the Inorganic Analysis Working Group (IAWG) of CCQM to assess and document the capabilities of the national metrology institutes (NMIs) or the designated institutes (DIs) to measure the mass fractions of trace elements (K, Cu and I) in infant formula. Government Laboratory, Hong Kong SAR (GLHK) acted as the coordinating laboratory.In CCQM-K125, 25 institutes submitted the results for potassium, 24 institutes submitted the results for copper and 8 institutes submitted the results for iodine.For examination of potassium and copper, most of the participants used microwave-assisted acid digestion methods for sample dissolution. A variety of instrumental techniques including inductively coupled plasma mass spectrometry (ICP-MS), isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), atomic absorption spectrometry (AAS), flame atomic emission spectrometry (FAES) and microwave plasma atomic emission spectroscopy (MP-AES) were employed by the participants for determination. For analysis of iodine, most of the participants used alkaline extraction methods for sample preparation. ICP-MS and ID-ICP-MS were used by the participants for the determination.Generally, the participants' results of CCQM-K125 were found consistent for all measurands according to their equivalence statements. Except with some extreme values, most of the participants obtained the values of di /U(di ) within ± 1 for the measurands.Main textTo 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 the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The determination of chlorine in plastic using isotope dilution inductively coupled plasma mass spectrometry

The determination of chlorine (Cl) in plastic using isotope dilution inductively coupled plasma mass spectrometry (ID-ICPMS) combined with different sample pretreatment procedures was examined in the present study.