International Reference Materials Research Articles

High–precision determination of carbon stable isotope in silicate glasses by secondary ion mass spectrometry: Evaluation of international reference materials

Secondary ion mass spectrometry (SIMS) has been used for isotope analysis of volatile components dissolved in silicate melts for decades. However, carbon in situ stable isotope analysis in natural silicate glasses has remained particularly challenging, with the few published attempts yielding high uncertainties. In this context, we characterized 31 reference silicate glasses of basaltic and basanitic compositions, which we then used as reference materials to calibrate δ13C − value analyses in silicate glasses by SIMS. This set of reference materials covers a wide range of CO2 concentrations (380 ppm – 12,000 ppm) and δ13C values (−28.1 ± 0.2 to −1.1 ± 0.2 ‰, ±1σ). The sets of reference materials were analyzed using large−geometry SIMS at two ion microprobe facilities to test reproducibility across different instrumental setups. The instrumental mass fractionation (IMF) varied widely with two different large−geometry SIMS instruments as well as with different analytical parameters such as field aperture size and primary beam intensity. We found that a precision better than ±1.1 ‰ (both average internal and external precision, ±1σ) for CO2 content higher than 1800 ppm could be achieved using a primary beam intensity of less than 5 nA, resulting in a final spot size of 10–20 μm, allowing precise analysis of δ13C in mineral−hosted melt inclusions. This level of precision was achieved at CO2 concentrations as low as 1800 ppm. This advance opens a wide range of new possibilities for the study of δ13C − value in mafic melts and their mantle sources. The reference materials are now available at the CNRS–CRPG ion microprobe facility in Nancy, France and will be deposited at the Smithsonian National Museum of Natural History, Washington, USA where they will be freely available on loan to any researcher.

Sulfur isotope analyses using 3× elemental analysis/isotope ratio mass spectrometry: Saving helium and energy while reducing analytical time and costs.

Helium (He) and energy shortages have caused price increases and reduced their availability. Using three combustion reactions per acquisition of carbon and nitrogen isotope ratios saves 50% He and energy during the elemental analysis/isotope ratio mass spectrometry (EA/IRMS). This approach needs to be tested for sulfur isotope (δ34S) analyses. A new method to measure δ34S in three sequential combustion reactions within one EA/IRMS acquisition was developed. The same material or blank samples could be used in the three reactions. After SO2 was used, a N2 purging method was employed to prolong the lifetime of the valves in the EA/IRMS interface. The 3×EA/IRMS was applied to measure δ34S in precious samples, such as Ag2S from acid-volatile and chromium-reducible sulfur extracted with a multiple-port setup. The 3×EA/IRMS-δ34S method was validated with replicate analyses of international reference materials and laboratory standards with a wide range of mineralogical compositions and δ34S values. The method provided a strategic advantage for the δ34S measurements of small precious samples (measured between blanks). The accuracy and precision of the 3×EA/IRMS values effectively matched those obtained using conventional EA/IRMS, with good agreement between the mean ± SD values and the recommended values with their uncertainties. Compared with the conventional EA/IRMS, the proposed method provides accurate and precise δ34S measurements of the sulfate and sulfide samples while saving approximately 50% of He, energy, SO2 reference gas, O2, analysis time, and cost. Notably, 3×EA/IRMS can provide up to three δ34S values unaffected by memory effects.

Discrepancies between two total IgE assays and difference in reference intervals in healthy adults

ObjectiveTo compare total immunoglobulin (Ig) E assay performance characteristics between Abbott Architect and Siemens Immulite test systems. Reference intervals were also determined for both platforms in an American population of healthy adults. MethodsAgreement of the two total IgE assays was evaluated in a cohort of 331 subjects with normal complete blood count (CBC) and comprehensive metabolic panel (CMP) results. Reference intervals were established in 302 subjects after exclusion of atopic individuals on the Abbott Architect and Siemens Immulite test systems. ResultsWe demonstrated a 32% positive bias for total IgE quantitation on the Siemens Immulite platform compared to the Abbott Architect, despite both methods calibrated against the same WHO international reference material (75/502), Furthermore, the upper limit of the reference interval (95th percentile) was determined to be higher for the Siemens Immulite assay compared to the Abbott Architect (132 and 102 IU/mL, respectively). ConclusionDespite the use of a common WHO reference material for total IgE assay calibration, significant differences in quantitation was observed between two FDA-cleared test systems. Given that, it is warranted for clinical laboratories to verify vendor established reference intervals and adjust accordingly based on internal assessment of the normal range.

Analytical and clinical validation of a novel, laboratory-developed, modular multiplex-PCR panel for fully automated high-throughput detection of 16 respiratory viruses

Background: Viral respiratory Infections pose a health risk, especially to vulnerable patient populations. Effective testing programs can detect and differentiate these infections at an early stage, which is particularly important for high-risk clinical departments. The objective of this study was to develop and validate a multiplex PCR-panel for 16 different respiratory viruses on a fully-automated high-throughput platform. MethodsThree multiplex-PCR assays were designed to run on the cobas5800/6800/8800 systems, consolidating 16 viral targets: RESP1: SARS-CoV-2, influenza-A/B, RSV; RESP2: hMPV, hBoV, hAdV, rhino-/ENV; RESP3: HPIV-1–4, hCoV-229E, hCoV-NL63, hCoV-OC43, hCoV-HKU1. Analytic performance was evaluated using digital-PCR based standards and international reference material. Clinical performance was determined by comparing results from clinical samples with reference assays. ResultsAnalytical sensitivity (i.e. lower limit of detection (LoD), 95 % probability of detection) was determined as follows: SARS-CoV-2: 29.3 IU/ml, influenza-A: 179.9 cp/ml, influenza-B: 333.9 cp/ml and RSV: 283.1 cp/ml. LoDs of other pathogens ranged between 9.4 cp/ml (hCoV-NL63) and 21,419 cp/ml (HPIV-2). Linearity was verified over 4–7 log-steps with pooled standard differentials (SD) ranging between 0.18–0.70ct. Inter-/intra-run variability (precision) was assessed for all targets over 3 days. SDs ranged between 0.13–0.74ct. Positive agreement in clinical samples was 99.4 % and 95 % for SARS-CoV-2 and influenza-A respectively. Other targets were in the 80–100 % range. Negative agreement varied between 96.3–100 %. DiscussionLab-developed tests are a key factor for effective clinical diagnostics. The multiplex panel presented in this study demonstrated high performance and provides an easily scalable high-throughput solution for respiratory virus testing, e.g. for testing in high-risk patient populations.

Longitudinal evaluation of external quality assessment results for CA 15-3, CA 19-9, and CA 125.

Tumor markers are established laboratory tools that help to diagnose, estimate prognosis, and monitor the course of cancer. For meaningful decision-making in patient care, it is essential that methods and analytical platforms demonstrate high sensitivity, specificity, precision, and comparability. Regular participation at external quality assessment (EQA) schemes is mandatory for laboratories. Here, a longitudinal evaluation of EQA data was performed to assess the performance of tumor marker assays over time. Longitudinal data of the cancer antigens (CA) 15-3 (n = 5,492), CA 19-9 (n = 6,802), and CA 125 (n = 5,362) from 14 INSTAND EQAs conducted between 2019 and 2023 were evaluated. A median of 197, 244 and 191 laboratories participated at the EQAs for CA 15-3, CA 19-9 and CA 125, respectively. Data evaluation encompasses intra- and inter-manufacturer specific variations over time, assay precision, and adherence to the EQA limits of ±24% for CA 15-3, ±27% for CA 19-9 and ±36% for CA 125. The study showed median manufacturer-dependent differences of up to 107% for CA 15-3, 99% for CA 125, and even 549% for CA 19-9 between the highest and the lowest methods over the studied period. Regarding the normalized median of all methods, the values of the most deviant methods were 0.42 for CA 15-3, 7.61 for CA 19-9, and 1.82 for CA 125. Intra-manufacturer variability was generally low, with median coefficients of variation (CV) below 10%. As the methods were evaluated according to method-specific consensus values, most participants passed the EQAs within the acceptance criteria. When the criteria were consistently set at 24%, the central 90% of participants passed the EQAs in 78.6%-100% for CA 15-3 (with exception of AX), 89.3%-100% for CA 125, and 64.3%-100% for CA 19-9. While intra-method precision of most analytical platforms is acceptable for all three tumor markers, considerable inter-method variability was observed over the whole studied period demonstrating the necessity for better standardization and harmonization of the methods, development of international reference materials, and comprehensive commutability studies with patient samples.

Reference value of the JNdi-1 isotopic material without normalization

The most used international reference material for neodymium isotope ratio is the JNdi-1 standard. The literature reference values were evaluated by Thermal Ionization Mass Spectrometry (TIMS) and using a conventional...

Performance report of the MICADAS at the Ocean University of China

The Ocean University of China radiocarbon accelerator mass spectrometer center (OUC-CAMS) is equipped with a mini carbon dating system (MICADAS) from the Ionplus AG. The MICADAS allows measurements of both graphite and CO2 samples because of the design of a hybrid ion source. Also, both 13C and 14C of organic samples can be measured at the same time because a stand-alone IRMS is coupled to the MICADAS. The OUC-CAMS provides routine 14C analyses on bulk organic carbon of various types, such as sediments, particulate matter, plant fragments, and compound-specific lipid biomarkers. Here we report the performance based on continuous analysis of international reference materials of 195 graphite data and 605 gas data carried out over the 2.5 years before 2022.

Deep Sequencing and Molecular Characterisation of BK Virus and JC Virus WHO International Reference Materials for Clinical Diagnostic Use.

Reactivation of JC and BK polyomaviruses during immunosuppression can lead to adverse clinical outcomes. In renal transplant recipients, BKV-associated nephropathy can result in graft loss, while in patients with autoimmune disorders, prolonged immunomodulatory drug use can cause rare onset of progressive multifocal leukoencephalopathy due to JCV reactivation. In such patients, accurate BK and JC viral load determinations by molecular technologies are important for diagnosis and clinical management; however, comparability across centres requires effective standardisation of diagnostic molecular detection systems. In October 2015, the WHO Expert Committee for Biological Standardisation (ECBS) established the 1st WHO International Standards (ISs) for use as primary-order calibrants for BKV and JCV nucleic acid detection. Two multi-centre collaborative studies confirmed their utility in harmonising agreement across the wide range of BKV and JCV assays, respectively. Previous Illumina-based deep sequence analysis of these standards, however, identified deletions in different regions, including the large T-antigen coding region. Hence, further detailed characterization was warranted. Comprehensive sequence characterisation of each preparation using short- and long-read next-generation sequencing technologies was performed with additional corroborative independent digital PCR (dPCR) determinations. Potential error rates associated with long-read sequencing were minimised by applying rolling circle amplification (RCA) protocols for viral DNA (circular dsDNA), generating a full validation of sequence identity and composition and delineating the integrity of full-length BK and JC genomes. The analysed genomes displayed subpopulations frequently characterised by complex gene re-arrangements, duplications and deletions. Despite the recognition of such polymorphisms using high-resolution sequencing methodologies, the ability of these reference materials to act to enhance assay harmonisation did not appear significantly impacted, based on data generated by the 2015 WHO collaborative studies, but highlights cautionary aspects of IS generation and commutability for clinical molecular diagnostic application.

An integrated geochemical spatial and temporal survey of thermal springs to characterize the geothermal resource of a volcano (Piton des Neiges, Réunion Island)

Geothermal exploration can be challenging in the absence of obvious surface indicators of a high enthalpy geothermal resource such as geysers, fumaroles or thermal springs with temperatures near 100 °C. This is the case at the Piton des Neiges volcano (Réunion Island), which displays evidence of hydrothermal activity mostly as thermal springs with temperatures not exceeding 50 °C, affected by mixing and reequilibration, and emerging in a complex geological framework, resulting from the polygenic history of this dormant volcano. Yet, these thermal springs keep a partial record of the reservoir geochemistry. Here, we propose an exploration method to set this thermal signature apart from the contribution of other processes and trace back the equilibrium conditions, enabling us to locate thermal fluid circulations, and evaluate their temperature and availability. We report its application at Piton des Neiges volcano. We led an extensive geochemical survey which nearly doubled the number of thermal springs reported on the volcano and dramatically extended the existing geochemical database in space and time. In tandem, we also monitored δ18O and δD values in rainwaters and thermal springs over two years to compare their temporal variations.Our surveys show that the repartition of thermal springs is controlled by only one of the volcanic rift zones (the N30°E axis), which is thus identified as the heat source of hydrothermal circulations. This N30°E rift zone is also a preferential pathway for the degassing of mantellic CO2. In addition, the composition of thermal waters is influenced by syenite intrusions along the rim of the caldera, acting as drains for the uprise of hydrothermal waters. O, H and Sr isotopic signatures of springs show that the geothermal resource of Piton des Neiges is in fact made of two independent and unconnected hydrothermal systems on the northern and southern circular depressions of the volcano (the cirques of Salazie and Cilaos, respectively). Their recharge is meteoric, multi-year, and mostly achieved by cyclonic events. Thermal waters experience reequilibration during their ascent and various degrees of CO2 input or degassing. Last equilibrium temperatures of water/rock interaction, estimated by multicomponent geothermometry, reach up to 125 ± 6 °C in the cirque of Salazie, and up to 141 ± 15 °C in the cirque of Cilaos, with possibility for hotter waters before reequilibration. Taken together, our results suggest that the most promising target for future exploration is located in the cirque of Cilaos, along the caldera rim, and in proximity of syenite intrusions.With a thorough prospecting of thermal springs, a comprehensive geochemical study and a geochemical monitoring of the different water reservoirs, we improved our understanding of the geothermal resource and identified future exploration targets at Piton des Neiges volcano.A separation scheme for strontium and light rare earth elements and its application to the isotopic analysis of strontium and neodymium in silicate rocks are presented. This method benefits from the selectivity and high capacity of two newly introduced extraction Chromatographic materials, referred to as Sr.Spec and TRU.Spec, respectively. These afford a straightforward separation of Sr and Sm + Nd with high yield, good purity and satisfactory blank levels, on very small (0.25 ml) columns using small volumes of solutions of a single mineral acid, HNO3. The validity of the method is illustrated by the measurement of 87Sr/ 86Sr and 143Nd/144Nd ratios in twelve international standard reference materials.

Light stable Cr isotope compositions of mid-ocean ridge basalts: Implications for mantle source composition

Stable isotopes of chromium (Cr) and iron (Fe), both multivalent elements in silicate melts, are valuable proxies of redox conditions in magmatic systems. Partial melting and fractional crystallization have been identified as the dominant fractionation processes for Cr and Fe isotopes in high-temperature reservoirs that can lead to small but detectable isotope variations in igneous rocks. More recently, however, the source mineralogy has been suggested to play an important role, which can ultimately affect the magnitude of Cr and Fe isotopic fractionation during partial melting and thus the Cr and Fe isotopic composition of the originating melt.With the aim to investigate the role of magmatic processes and the source Cr and Fe isotope signatures on the isotope composition of these transition metals in normal mid-ocean ridge basalts (N-MORB), we analyzed 21 well-characterized MORB glasses from the southern East-Pacific Rise, Pacific-Antarctic Ridge and Mid-Atlantic Ridge. The Cr isotope compositions of N-MORB show a narrow range from −0.278 to −0.186 ‰ in δ53/52Cr (i.e., difference of a sample’s 53Cr/52Cr ratio relative to the international reference material NIST SRM979), with an average value of −0.237 ± 0.050 ‰ (2SD; n = 19). As such, the average N-MORB δ53/52Cr value is significantly lower than that of Bulk Silicate Earth of −0.12 ± 0.06 ‰ and the Cr isotope compositions reported for most ocean island basalts ranging from ∼ −0.23 to 0.00 ‰. Iron isotopic compositions of these MORB range from +0.032 to +0.137 ‰ in δ56/54Fe (i.e., difference of a sample’s 56Fe/54Fe ratio relative to the international reference material IRMM014) and are within the range of previously published MORB data. The lack of correlations between N-MORB Cr isotope signatures and indices of magmatic differentiation suggests a negligible control of this process on Cr stable isotopes. Partial melting modeling using pMELTS provides evidence that the significant offset towards lower δ53/52Cr values of N-MORB cannot be produced by decompression partial melting of a lherzolithic source such as the depleted upper mantle alone. Instead, we suggest that the lower δ53/52Cr values of MORB could be linked to intrinsic small-scale 53Cr-depleted pyroxene-rich domains in the upper mantle that influence the melt’s Cr isotopic budget during partial melting.

Application of MARS-5 and UltraWAVE microwave systems to the digestion of silicate rocks followed by ICP-MS analysis

Two microwave systems MARS-5 and UltraWAVE are compared in the efficiency with regard to the digestion of silicate rocks with subsequent determination of 32 elements (Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Nb, Ta, Cs, Ba, 14 REE, Hf, Ta, Th, U) by inductively coupled plasma mass spectrometry (ICP-MS). The development of digestion methods and validation of the obtained results has been carried out using international reference materials — basalts BHVO-2 and BCR-2, serpentinite UB-N and peridotite JP-1. Microwave digestion included a two-stage treatment of samples with a mixture of concentrated acids HF, HNO3, HCl in MARS-5 (T = 190°C, P = 20 bar) and UltraWAVE (T = 240°C, P = 80 bar) with distillation of excess fluorides in the form of SiF4 between microwave digestion stages. The determination of concentrations in the obtained solutions was carried out on a high-resolution mass spectrometer ELEMENT in low and medium resolution according to external calibration with the internal standard (In), taking into account the acid composition of the analyzed solutions. The detection limits of the analytes after acid digestion in MARS-5 and UltraWAVE are comparable and provide the determination of all specified elements, except for Ta in JP-1. The use of the developed sample preparation procedure in MARS-5 ensures complete decomposition of BHVO-2, BCR-2, UB-N followed by ICP-MS determination of 32 specified elements in the obtained solutions without additional preconcentration steps. The relative standard deviations for the determined elements are 2 – 9% for the reference materials BHVO-2, BCR-2, 3 – 12% for UB-N with an increase to 16 – 25% (Nb, Ta) due to the approach to the detection limit. The more efficient microwave digestion in UltraWAVE compared to MARS-5 was proved by the complete decomposition of JP-1 with the transfer of all the elements, including Cr, to the solution.

Rubidium Isotope Ratios of International Geological Reference Materials

In this study we determined rubidium isotope ratios in twenty‐one commonly used international geological reference materials, including igneous, sedimentary and metamorphic rocks, as well as an IAPSO seawater reference material. All δ87Rb results were obtained relative to the NIST SRM 984 reference material. For most reference materials, Rb was purified using a single column loaded with Sr‐spec resin. For reference materials containing low Rb but high mass fractions of matrix elements (such as basic rock and seawater), Rb was purified using two‐column chromatography, with the first column packed with AGMP‐50 resin and the second column packed with Sr‐spec resin. Two methods for instrumental mass bias correction, sample‐standard bracketing (SSB) mode, and the combined sample‐standard bracketing and Zr internal normalisation (C‐SSBIN) method, were compared for Rb isotopic measurements by multi‐collector inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS). The long‐term reproducibility of Rb isotopic measurements using both methods was similar, better than 0.06‰ (2s, standard deviation) for NIST SRM 984. Significant Rb isotopic fractionation was observed among the reference materials, with an overall variation in δ87Rb values of approximately 0.5‰. The δ87Rb values of igneous rocks ranged from ‐0.28‰ to +0.06‰, showing a trend from heavier isotopic compositions in mafic rocks to lighter δ87Rb values in the more evolved felsic rocks. The sedimentary and metamorphic rocks had Rb isotope ratios similar to those of igneous rocks. The δ87Rb values of the reference materials related to low‐temperature geological processes showed a wider range than those of high‐temperature processes. Notably, the IAPSO seawater reference material had a δ87Rb value of +0.14‰, which deviated from that of igneous rocks, and represents the heaviest reservoir of Rb isotopes found thus far on Earth. The comprehensive dataset presented here has the potential to serve for quality assurance purposes, and provide a framework for interlaboratory comparisons of Rb isotope ratios.

Alder creek sanidine (ACs-a): New sampling and intercalibration for quaternary 40Ar/39Ar age monitoring

The 40Ar/39Ar dating method requires the utilization of a neutron flux monitoring reference material. Generally, the extracted sanidine from the rhyolite of Alder Creek, California, is regarded as a reliable indicator for Quaternary materials; however, its availability in many laboratories is still limited. A new sampling method of Alder Creek rhyolite, which could yield pure and fresh sanidine crystals designated as Alder Creek sanidine (ACs-a), could be used to produce a new batch of the reference material. Accordingly, in this work, the grains of sanidine were meticulously dated and calibrated against the international reference materials FCs, YBCs, and ACs-2. Additionally, at various grain sizes (>1000 μm and 1000–600 μm), the degree of homogeneity of the newly selected grains was evaluated and confirmed. Experiments involving total laser fusion and incremental heating were also conducted to compare the outcomes of the different applied protocols. In situ trace elemental analysis by electron microprobe analysis (EMPA) revealed the existence of consistent K content. Flat age spectra and average F-value (40Ar*/39ArK) relative standard deviations ranging from 0.36% to 0.51% for the different aliquots reveal the reproducibility of ACs-a and its appropriateness as a reliable 40Ar/39Ar standard. The calibrated age of ACs-a was 1.1888 ± 0.0048 Ma (0.40%, MSWD = 1.9) and the intercalibration factors (R-values) between ACs-a and FCs, YBCs, and ACs-2 were RFCsA−1 = 0.04184 ± 0.00030, RFCsA−4 = 0.04178 ± 0.00018, RYBCsA−2 = 0.04005 ± 0.00041, RYBCsA−5 = 0.03998 ± 0.00019, and RACs−2A−3 = 0.99271 ± 0.01148. These R-values enabled direct comparisons between ACs-a and other reference materials. The ACs-a grains are available from our laboratory upon request as a neutron fluence monitor.

Assessment of the accuracy of the 17 O correction algorithm used in δ13 C determinations by CO2 mass spectrometry.

High-accuracy δ13 C values are required for observations of greenhouse gases CO2 and methane, and, consequently, for international reference materials (RMs). Recently, another application, clumped isotope geothermometry of natural carbonates, has demonstrated the requirement for high-accuracy δ13 C values. δ13 C determinations by mass spectrometry use an 17 O isobaric correction on m/z 45, where 17 O abundance is calculated from the measured 18 O with the 17 O-18 O relationship assumed with λ = 0.528. This relationship is the key assumption of the algorithm proposed in 2003 and accepted by IUPAC in 2010. However, to date, this relationship and potential δ13 C biases have not been verified using 17 O measurements. To verify the 17 O correction and to estimate potential δ13 C biases, we compile measured 17 O data for carbonate RMs, for a range of natural carbonates that are typically analyzed in clumped isotope geothermometry and for CO2 in isotope equilibrium with natural waters including plants and biota. δ13 C biases are calculated based on 17 O deviation from the 17 O-18 O relationship assumed in the 17 O correction. To estimate δ13 C biases accurately, the VPDB-CO2 framework for expressing 17 O excess is defined and linked to the δ13 C scale definition. δ13 C biases estimated for carbonate RMs are found within ±0.004‰; the biases estimated for natural carbonates and CO2 in equilibrium with natural waters are mostly within ±0.010‰ (bidirectional distribution around zero). In all cases, the estimated biases are found within the best instrumental uncertainty of modern isotope ratio mass spectrometry (IRMS) (around ±0.014‰, k = 2). For the first time, high accuracy of δ13 C data obtained by CO2 mass spectrometry using the 17 O correction with fixed λ = 0.528 has been demonstrated using measured 17 O data. δ13 C biases estimated are within the best IRMS precision (±0.014‰, k = 2) and can be neglected in most practical applications. To obtain high-quality δ13 C data, it is strictly necessary that all data are treated on the VPDB-CO2 scale.

Improving the routine analysis of siderite for δ13 C and δ18 O in environmental change research.

The carbon (δ13 C) and oxygen (δ18 O) isotope composition of siderite (FeCO3 ) is used widely to understand and quantify geochemical processes to reconstruct past climate and environmental change. However, few laboratories follow precisely the same protocol for the preparation and analysis of siderite-bearing materials, which combined with the absence of international reference materials and mineral-specific acid fractionation factors, leads potentially to significant differences in isotope data generated by individual laboratories. Here we examine procedures for the isotope analysis of siderite and discuss factors potentially contributing to inconsistencies in sample measurement data. Isotope analysis of siderite is first assessed using similar versions of the classical off-line, sealed vessel acid digestion method by comparing data sets obtained from intercomparison materials measured at two participating laboratories. We then compare data from the classical method against those generated using an automated preparation technique using data produced from an independent set of test materials. Measurement of siderite δ13 C is generally both repeatable and reproducible, but measurement of δ18 O may be subject to large (~1‰), method-dependent bias for siderite reacted at differing temperatures (70°C and 100°C) under classical and automated CO2 preparation conditions. The potential for poor oxygen isotope measurement reproducibility is amplified by local differences in sample preparation protocols and procedures used to calibrate measurement data to international reference scales. We offer suggestions for improving the repeatability and reproducibility of δ13 C and δ18 O analysis on siderite. The challenge of producing consistent isotope data from siderite can only be resolved by ensuring the availability of siderite reference materials to facilitate identical treatment as a basis for minimising method-dependent contributions to data inconsistency between laboratories.

High-precision lithium isotopic analysis using the Nu Sapphire MC-ICP-MS

With single-column chemical purification, highly accurate δ7Li values for eight international reference materials are presented together with seventeen Chinese geological reference materials from NRCG using the Nu Sapphire.

High precision measurements of lithium isotopic composition at sub-nanogram by MC-ICP-MS with membrane desolvation.

The geochemistry of Li and Li isotopes is a promising tracer of chemical weathering processes for both modern and ancient times. Therefore, accurate and precise determination of the isotopic composition of Li is required for a large variety of complex geological samples with different Li concentrations and matrix/Li ratios. Especially, geochemical studies of precious geological samples with ultra-low lithium content and high matrix. In this study, the accuracy and the precision corresponding to Li isotopic measurements of low-level samples using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with membrane desolvation introduction system was evaluated. The method of MC-ICP-MS with membrane desolvation and a high-sensitivity X-skimmer cone, together with a simple one-step column separation enabled the high-precision isotopic analysis of Li quantities as small as 2 ng. The long-term instrumental external reproducibility of δ7Li values for the L-SVEC and SPEX-Li were 0.0 ± 0.1‰ (n = 20) and 12.1 ± 0.4‰ (n = 20), respectively. Based on the measurements on a series of international reference materials over the last two years. The measured δ7Li values for the standards with a variety of matrices, including BHVO-2, AGV-2 and seawater (NASS-6). The δ7Li values of BHVO-2 (4.58 ± 0.35‰), AGV-2 (6.85 ± 0.40‰) and NASS-6 (30.88 ± 0.20‰) are in agreement with the published data within the uncertainty. We also present analytical results for South China Sea surface seawater water, meteorite, limestones and rain water. These results demonstrate the validity of the method for obtaining highly precise and accurate outcomes.

Collision course; high-precision mass-independent and mass-dependent calcium isotope measurements using the prototype collision cell MC-ICPMS/MS, Proteus

This paper reports measurements of mass-independent and mass-dependent Ca isotope variations using the prototype collision cell MC-ICPMS/MS, Proteus. Helium and hydrogen gases are introduced into the collision cell and the well characterised resonant charge exchange and proton transfer reactions between Ar+ ions and H2 molecules results in almost complete removal of the 40Ar+ ions allowing the measurement of the 40Ca isotope by MC-ICPMS without resorting to ‘cold’ plasma.A range of reference materials have been characterised for both their mass-independent and mass-dependent Ca isotope compositions relative to the international reference material NIST SRM 915a. Notably, the radiogenic 40Ca/44Ca isotope ratio (internally normalised to 42Ca/44Ca) can be accurately measured with typical reproducibility better than 40 ppm (pooled 2 SD) for a single measurement using 12 μg of Ca. Reference materials USGS GSP‐2 and CRPG FKN have notably radiogenic 40Ca/44Ca, with values of 434 ± 7 and 5513 ± 17 ppm respectively relative to NIST SRM 915a (pooled 2 SE, n = 35 and 5 respectively). In contrast, multiple repeat measurements of mantle derived reference materials BIR, BHVO-2, BCR-2 and JP-1 yield values that are slightly unradiogenic (mean − 23 ± 5 ppm, pooled 2 SE, n = 71) relative to NIST SRM 915a, bone ash and seawater reference materials, likely reflecting crustal components in the latter. Coupled measurements of the minor 48Ca and 43Ca isotopes give 48Ca/44Ca and 43Ca/44Ca (internally normalised to 42Ca/44Ca) with typical reproducibilities of ± 40 and ± 16 ppm respectively (pooled 2 SD) for single (24 μg Ca) analyses. Multiple repeats yield mean values for terrestrial reference materials that are within their pooled 2 SE uncertainties of SRM 915a, to precisions of ± 15 and ± 6 ppm respectively. Measurements of mass-dependent Ca isotope variations (δ44/40Ca) have been made using a 42Ca-43Ca double spike isotope tracer together with measurements of 40Ca and 44Ca and have typical reproducibilities of ± 0.035 ‰ (pooled 2 SD) for single (12 μg) analyses. Measured δ44/40Ca values for reference materials are within uncertainty of previously reported values. Moreover, given that the double spike inversion uses the same isotopes as the mass independent determinations of 40Ca/44Ca and 43Ca/44Ca, our documentation of the absence of anomalies at a precision of better than 20 ppm in a range of low K/Ca terrestrial reference materials implies that the accuracy of our δ44/40Ca analyses is at this level of uncertainty.

An easy, fast, and efficient assay for the quantification of peptide Hepcidin-25 in serum and plasma with LC-MS/MS.

The peptide hormone hepcidin-25 plays an important role in iron metabolism. Low or high levels of hepcidin-25 are associated with various iron disorders; therefore, hepcidin-25 is an important biomarker. This study describes an easy and fast analytical assay for the quantification of hepcidin-25 with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Sample preparation was performed by protein precipitation with trichloroacetic acid, and injection onto a LC-MS/MS was directly conducted from a LoBind 96-well plate. The concentration range covered by the quality control samples, ranged from 0.25nmol/L (12.3% CV) to 11.9nmol/L (CV < 9%). Matrix effect was limited (mean recovery of 99.9% with a CV of 6.4%). The assay was validated for serum, EDTA and heparin plasma. An international secondary reference material was used for calibration. The reference interval (90% CL) was estimated for hepcidin-25 by analysing serum and plasma samples from 156 healthy subjects with a lower limit: 0.12 (0.07-0.19) and upper limit: 11.2nmol/L (9.5-13.0). We present a fast and easy assay for the quantification of hepcidin-25 in serum and plasma samples. The assay was successfully used for the detection of various forms of hereditary haemolytic anaemias, to characterize the interplay between erythropoiesis and iron levels.

Comparison of a novel automated DiaSys procalcitonin immunoassay with four different BRAHMS-partnered immunoassays

ObjectivesProcalcitonin (PCT) is an important biomarker of sepsis and respiratory infections. Various automated immunoassays for measuring PCT in patient plasma are available in medical laboratories. However, due to a lack of international reference material for PCT, the assays are not always comparable. Design and methodsIn this study, we compared a new turbidimetric immunoassay from DiaSys, measured on the Abbott Architect c16000 and Alinity c, with four BRAHMS-associated chemiluminescence immunoassays (Abbott Architect i2000SR, Alinity i, Roche Cobas e411 and DiaSorin Liaison XL) using 120 random patient plasma samples from the clinical laboratory routine at the University Medical Center Goettingen. ResultsThe DiaSys assay showed clear differences as compared to the BRAHMS-associated assays when measured on Architect c: i.e. 58% positive mean bias vs. Architect i, 67% vs. Cobas and 23% vs. Liaison. As a result, additional 19% our patients would have a suspected bacterial infection, when using PCT values from the DiaSys assay and commonly accepted decision limits. A crosscheck of the DiaSys calibrator on the BRAHMS-associated systems showed a low recovery of the calibrator material (approx. 50%). ConclusionsOverall, this study shows significant differences between the DiaSys and BRAHMS-associated assays. This could be attributed to a potential DiaSys calibrator problem. This highlights the need for an international reference material for harmonization of the PCT assays.