Isotope Dilution Research Articles

Correction of creatine-creatinine conversion during serum creatinine quantification by two-dimensional liquid chromatography and double-spike isotope dilution tandem mass spectrometry

Background and aimsDevelopment of a candidate reference method based on bidimensional liquid chromatography coupled to ESI-MS/MS and double spike isotope dilution for serum creatinine quantification capable of correcting for creatinine-creatine interconversion during sample pretreatment. Study of the impact of the creatine-creatinine interconversion during the analysis of human serum samples. Materials and methods13C1-creatinine and 13C2-creatine are added to the serum sample. Separation carried out by bidimensional liquid chromatography combining reversed phase and a strong cation exchange chromatography. The heart cut, containing creatine and creatinine, is automatically transferred to the second dimension. Quantification carried out by double spike isotope dilution tandem MS/MS. ResultsMinimization of spectral interferences and ion suppression due to matrix effects while increasing sample throughput compared to the direct coupling of cation exchange chromatography to the ESI source. Trueness of the method studied with the satisfactory analysis of two certified reference materials. Satisfactory intra- and inter-day precisions obtained analysing a serum pool and control sera. Analysis of 93 serum samples revealed negligible interconversions with no correlation with creatine levels. ConclusionsThe method provides adequate analytical figures of merit for serum creatinine determination according to CSLI guidelines. Negligible creatine-creatinine interconversion is promoted with the applied sample preparation procedure.

Transdermal application of H100 gel to the penile shaft in patients with Peyronie's disease infiltrates the tunica albuginea.

Treatment options for Peyronie's disease (PD) remain limited. Topical H100 gel, (Hybrid Medical, Edina, USA), which contains nicardipine, super oxide dismutase and emu oil showed safety and efficacy in a previous small double-blind placebo-controlled pilot study. The present study evaluates if topically applied H100 gel applied to the penile shaft infiltrates the tunica albuginea. Nicardipine is a key active ingredient in H100 and serves as a surrogate marker. Three men already scheduled to undergo a planned surgical procedure for PD applied commercially available H100 gel twice daily to the penile shaft for up to 30 days prior to the procedure. Tunica albuginea samples were obtained at surgery. Nicardipine evaluation was performed using isotope dilution technique via liquid-chromatograph-mass spectrometry (LCMS). All three patients tolerated H100 gel application without side effects. All three tunica albuginea specimens showed detectable nicardipine in the tunical tissue. Transdermal application of commercially available H100 gel is able to penetrate the tunica albuginea tissue and is detectable in men with acute and chronic PD. This finding may support the encouraging results found in the prior H100 pilot study.

Late Kungurian Radioisotope Age of the Boundary Between the Balakhonka and Kolchugino Groups in the Kuznetsk Basin (Western Siberia, Russia) – Additional Evidence for the Validity of the Ufimian Stage of the East European Permian

This article discusses the Late Kungurian radioisotopic age (276.9 ± 0.4 Ma) of the middle part of the Starokuznetsk Formation (Kuznetsk Subgroup, Kolchugino Group) of the Kuznetsk Basin determined by chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS). The analysis of the biostratigraphic data confirms that the layer dated belongs to the interval in which the Balakhonka Flora (cordaitoid) was replaced by the Kolchugino Flora (fern-pteridosperm-cordaitoid). This indicates that the change from the Balakhonka Flora to the Kolchugino Flora in the low latitudes of Angaraland took place during the Late Kungurian. The data obtained were used for direct correlation of the lower part of the Kolchugino Group with the Upper Kungurian of the International Chronostratigraphic Chart. Similar sequences of non-marine bivalve assemblages in the Permian successions of Angaraland (giant Prokopievskia, Khosedaella-Redikorella-Palaeomutela, and dominant Palaeomutela) and Eastern Europe (giant Sinomya, Palaeomutela-Khosedaella-Redikorella, and dominant Palaeomutela) further support the validity of the correlation of the Kuznetsk Subgroup with the Ufimian Stage. The placement of the lower boundary of the Kolchugino Group in the upper part of the Kungurian Stage of the International Chronostratigraphic Scale raises the question of the continuation of the Ufimian Stage as an independent straton in the East European Stratigraphic Scale. Its lower boundary coincides with the beginning of the change in the Balakhonka and Kolchugino Flora in the low latitudes of Angaraland, as well as with the faunal exchanges between the Euramerican and Angarian non-marine bivalve assemblages.

Effects of endocrine disrupting chemicals and their interactions with genetic risk scores on cardiometabolic traits

Ubiquitous non-persistent endocrine disrupting chemicals (EDCs) have inconsistent associations with cardiometabolic traits. Additionally, large-scale genome-wide association studies (GWASs) have yielded many genetic risk variants for cardiometabolic traits and diseases. This study aimed to investigate the associations between a wide range of EDC exposures (parabens, bisphenols, and phthalates) and 14 cardiometabolic traits and whether these are moderated by their respective genetic risk scores (GRSs). Data were from 1074 participants aged 18 years or older of the Lifelines Cohort Study, a large population-based biobank. GRSs for 14 cardiometabolic traits were calculated based on genome-wide significant common variants from recent GWASs. The concentrations of 15 EDCs in 24-hour urine were measured by isotope dilution liquid chromatography tandem mass spectrometry technology. The main effects of trait-specific GRSs and each of the EDC exposures and their interaction effects on the 14 cardiometabolic traits were examined in multiple linear regression. The present study confirmed significant main effects for all GRSs on their corresponding cardiometabolic trait. Regarding the main effects of EDC exposures, 26 out of 280 EDC-trait tests were significant with explained variances ranging from 0.43 % (MMP- estimated glomerular filtration rate (eGFR)) to 2.37 % (PrP-waist-hip ratio adjusted body mass index (WHRadjBMI)). We confirmed the association of MiBP and MBzP with WHRadjBMI and body mass index (BMI), and showed that parabens, bisphenol F, and many other phthalate metabolites significantly contributed to the variance of WHRadjBMI, BMI, high-density lipoprotein (HDL), eGFR, fasting glucose (FG), and diastolic blood pressure (DBP). Only one association between BMI and bisphenol F was nominally significantly moderated by the GRS explaining 0.36 % of the variance. However, it did not survive multiple testing correction. We showed that non-persistent EDC exposures exerted effects on BMI, WHRadjBMI, HDL, eGFR, FG, and DBP. However no evidence for a modulating role of GRSs was found.

Geochronological and geochemical effects of zircon chemical abrasion: insights from single-crystal stepwise dissolution experiments

Abstract. Chemical abrasion in hydrofluoric acid (HF) is routinely applied to zircon grains prior to U–Pb dating by isotope dilution thermal ionization mass spectrometry (ID-TIMS) to remove radiation-damaged portions of grains affected by Pb loss. Still, many chemically abraded datasets exhibit evidence of residual Pb loss. Here we test how the temperature and duration of chemical abrasion affect zircon U–Pb and trace element systematics in a series of 4 h, single-crystal stepwise dissolution experiments at 180 and 210 ∘C. Microtextural data for the zircon samples studied are presented in a companion paper by McKanna et al. (2023). We find that stepwise dissolution at 210 ∘C is more effective at eliminating material affected by open-system behavior and enriched in U, common Pb (Pbc), and light rare earth elements (LREEs); reduces the presence of leaching-induced artifacts that manifest as reverse discordance; and produces more consistent and concordant results in zircon from the three rocks studied. We estimate that stepwise dissolution in three 4 h steps is roughly equivalent to a single ∼ 8 h leaching step due to the insulating properties of the PTFE sleeve in the Parr pressure dissolution vessel, whereas traditionally labs utilize a single 12 h leaching step. We conclude that a single 8 h leaching step at 210 ∘C should remove Pb loss effects in the majority of zircon and that this can be used as an effective approach for routine analysis. Further, we calculate time-integrated alpha doses for leachates and residues from measured radionuclide concentrations to investigate (1) the alpha dose of the material dissolved under the two leaching conditions and (2) the apparent minimum alpha dose required for Pb loss susceptibility: ≥ 6×1017 α g−1.

Speciation and cycling of iodine in the subtropical North Pacific Ocean

Iodine intersects with the marine biogeochemical cycles of several major elements and can influence air quality through reactions with tropospheric ozone. Iodine is also an element of interest in paleoclimatology, whereby iodine-to-calcium ratios in marine carbonates are widely used as a proxy for past ocean redox state. While inorganic iodine in seawater is found predominantly in its reduced and oxidized anionic forms, iodide (I−) and iodate (IO3−), the rates, mechanisms and intermediate species by which iodine cycles between these inorganic pools are poorly understood. Here, we address these issues by characterizing the speciation, composition and cycling of iodine in the upper 1,000 m of the water column at Station ALOHA in the subtropical North Pacific Ocean. We first obtained high-precision profiles of iodine speciation using isotope dilution and anion exchange chromatography, with measurements performed using inductively coupled plasma mass spectrometry (ICP-MS). These profiles indicate an apparent iodine deficit in surface waters approaching 8% of the predicted total, which we ascribe partly to the existence of dissolved organic iodine that is not resolved during chromatography. To test this, we passed large volumes of seawater through solid phase extraction columns and analyzed the eluent using high-performance liquid chromatography ICP-MS. These analyses reveal a significant pool of dissolved organic iodine in open ocean seawater, the concentration and complexity of which diminish with increasing water depth. Finally, we analyzed the rates of IO3− formation using shipboard incubations of surface seawater amended with 129I−. These experiments suggest that intermediate iodine species oxidize to IO3− much faster than I− does, and that rates of IO3− formation are dependent on the presence of particles, but not light levels. Our study documents the dynamics of iodine cycling in the subtropical ocean, highlighting the critical role of intermediates in mediating redox transformations between the major inorganic iodine species.

Quantification of mRNA in Lipid Nanoparticles Using Mass Spectrometry.

Lipid nanoparticle-encapsulated mRNA (LNP-mRNA) holds great promise as a novel modality for treating a broad range of diseases. The ability to quantify mRNA accurately in therapeutic products helps to ensure consistency and safety. Here, we consider a central aspect of accuracy, measurement traceability, which establishes trueness in quantity. In this study, LNP-mRNA is measured in situ using a novel liquid chromatography-mass spectrometry (LC-MS) approach with traceable quantification. Previous works established that oligonucleotide quantification is possible through the accounting of an oligomer's fundamental nucleobases, with traceability established through common nucleobase calibrators. This sample preparation does not require mRNA extraction, detergents, or enzymes and can be achieved through direct acid hydrolysis of an LNP-mRNA product prior to an isotope dilution strategy. This results in an accurate quantitative analysis of mRNA, independent of time or place. Acid hydrolysis LC-MS is demonstrated to be amenable to measuring mRNA as both an active substance or a formulated mRNA drug product.

A high-throughput small volume matrix based calibration using isotope dilution liquid chromatography tandem mass spectrometry analysis for 42 per and polyfluoroalkyl substances in groundwater

A novel method for the determination of per- and polyfluoroalkyl substances (PFAS) in groundwater is presented using a subsample, matrix-matched calibrators, 96-well plate solid phase extraction (SPE), and ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Accuracy, precision, measurement of uncertainty (MOU), method detection limit (MDL), method quantitation limit (MQL), analytical measurement range, interferences/ion suppression, and analyte stability were determined as part of the in-house method validation. The method quantitates 42 PFAS compounds from nine different compound classes. Accuracy for the reference material (RM) and matrix spike (MS) ranged from 52.3 to 117.8 %, and precision for the MS and matrix spike duplicate (MSD) had a coefficient of variation (CV) from 2.0 % to 23.3 %. MDLs spanned from 0.07 to 1.97 ng L−1, with MQLs ranging from 0.20 to 5.90 ng L−1. Suppression studies determined that iron and manganese have effects on analytes that do not have paired isotopically labeled standards. The results from the in-house validation indicated that this Michigan Department of Health and Human Services laboratory developed test meets the necessary accuracy, precision, MDL, MQL and reporting limits requirement established by the laboratory's quality system essentials (QSEs) and select criteria from the Department of Defense (DoD) Quality Systems Manual for Environmental Laboratories and American Industrial Hygiene Association Laboratory Accreditation Program, LLC (AIHA LAP, LLC) accrediting International Standard Organization (ISO/IEC 17025:2017) check list.

Determination of [Glu1]-fibrinopeptide B purity by gas chromatography - isotope dilution mass spectrometry.

The present work assessed the purity of [Glu1]-fibrinopeptide B (GFB) as a model peptide using gas chromatography - isotope dilution mass spectrometry. GFB and various isotope-labeled amino acids were hydrolyzed in HCl and then derivatized using optimized procedures. The primary impurity in GFB was also identified and used to correct the final result. A method repeatability of 0.5% was achieved and linear calibrations were obtained for five amino acids. The LOD and LOQ were 0.041 to 0.096 μg g-1, and 0.16 to 0.56 μg g-1, respectively. The purity of GFB was found to be (0.715 ± 0.012) g g-1. This technique exhibited comparable accuracy to that obtainable from liquid chromatography - isotope dilution mass spectrometry but at lower cost. This method could be employed as a reference technique or in fields such as clinical diagnostics or bio-pharmaceutical peptide purity analysis.

A reliable quantification of organophosphorus pesticides in brown rice samples for proficiency testing using Japanese official analytical method, QuEChERS, and modified QuEChERS combined with isotope dilution mass spectrometry.

The objective of the present study is to provide reliable concentration values as assigned values for target pesticides in brown rice samples used in proficiency testing (PT) organized by the Hatano Research Institute (HRI). The test samples for PT were prepared by immersing brown rice in the pesticide solution and using a spray dryer by the HRI. Homogeneity and stability assessments were performed for PT samples, and the relative uncertainties due to inhomogeneity and instability were 0.58 %-0.78 % and 0 %-0.96 %, respectively. Quantification for the assigned values of target pesticides by the National Metrology Institute of Japan (NMIJ) was carried out using the multiple analytical methods including Japanese official analytical method, QuEChERS, and modified QuEChERS, which were combined with isotope dilution mass spectrometry, to ensure the reliability of the analytical results. The NMIJ assigned values were 0.065±0.004 mg/kg for chlorpyrifos, 0.217±0.012 mg/kg for diazinon, 0.138±0.008 mg/kg for fenitrothion, and 0.138±0.008 mg/kg for malathion.

Combination of isotope dilution with liquid chromatography-inductively coupled plasma mass spectrometry for the simultaneous monitoring and evaluation of cadmium and inorganic arsenic in polished rice.

A new monitoring and evaluation technique for cadmium (Cd) and inorganic arsenic (i-As) in rice was developed, where the isotope dilution (ID) method was applied in combination with high performance liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS), following heat-assisted extraction. Cadmium and i-As in a rice sample were extracted using the HNO3-H2O2 extractant, and an appropriate amount of enriched 111Cd was spiked into it. Cadmium and As species were measured simultaneously by LC-ICP-MS. The cadmium concentration was calculated from the isotope dilution analysis, and i-As was determined by the comparison (1 point calibration) method using additional 111Cd as an internal standard. The proposed method provides accurate and precise determination of Cd based on the isotope dilution analysis. Moreover, it can be applied to a rapid screening test to find contaminated rice samples, by means of monitoring the intensity ratios of natural 111Cd and i-As to the additional 111Cd. The developed technique was applied to analyzing multiple rice reference materials, and the measurement results of Cd and i-As agreed with the certified values within the uncertainty range. It is noted that the grain size of rice samples does not affect the extraction data, when the rice sample is crushed into powder less than 850 μm. The proposed method was very useful for the monitoring and evaluation of Cd and i-As in rice as a precise analytical method as well as a screening method.

A candidate reference measurement procedure for the quantification of α-synuclein in cerebrospinal fluid using an SI traceable primary calibrator and multiple reaction monitoring.

α-synuclein aggregation is an important hallmark of neurodegenerative diseases such as Parkinson's disease (PD) and Lewy body dementia. α-synuclein has been increasingly used as a diagnostic biomarker in PD and other synucleinopathies. Current clinical assays rely on antibody-based immunoassays to detect α-synuclein, which possess high sensitivity, afford high throughput and require small sample volumes. The utility of these assays, however, may be compounded by the specificity, selectivity and batch-to-batch heterogeneity of the antibody used, which can lead to deviations in the total amount of the protein measured when comparing results among different laboratories. Similarly, current mass spectrometry-based quantification methods for α-synuclein lack well-defined, value assigned calibrators to ensure comparability of measurements. Therefore, there is still an unmet need for the standardisation of clinical measurements for α-synuclein that can be achieved by the development of reference measurement procedures (RMPs) utilising calibrators traceable to the SI (International System of Units). Here, we report a candidate RMP for α-synuclein, using an SI traceable primary calibrator and an isotope dilution mass spectrometry (IDMS) approach to address this need. The gravimetrically prepared primary calibrator was traceably quantified utilising a combination of amino acid analysis (AAA) and quantitative nuclear magnetic resonance (qNMR) for value assignment. An optimised targeted sample clean-up procedure involving a non-denaturing Lys-C digestion and solid-phase extraction strategy was devised, followed by the development of a targeted multiple reaction monitoring (MRM) method for the quantification of α-synuclein in cerebrospinal fluid (CSF). This candidate RMP was then deployed for the sensitive detection and accurate quantification of multiple proteotypic α-synuclein peptides in patient derived CSF samples. The LC-MS based results were subsequently compared to immunoassay data to assess the overall performance of our approach. The development and adoption of this candidate RMP, along with the availability of the SI traceable primary calibrator will allow for reliable quantifications of α-synuclein in CSF by an LC-MS based assay. The RMP will potentially contribute towards the standardisation of this important biomarker and may lead to future interlaboratory comparisons.

CCQM-K160: platinum group elements in automotive catalyst

Main textThe platinum group elements (PGEs) play an important role in reducing emissions from automotive vehicles through their use in catalytic convertors but also for catalysis in the pharmaceutical industry. The immense economic value of platinum (Pt), palladium (Pd) and rhodium (Rh) highlights the importance of highly accurate measurements. Therefore, there is a need for National Metrology Institutes (NMIs) and Designated Institutes (DIs) to demonstrate measurement capability in this space.A pilot comparison (CCQM-P63) for precious metals in automotive catalyst took place in 2006, but with a limited number of institutes participating. Furthermore, this study was performed over 17 years ago. Therefore, there was a need to maintain existing capability and demonstrate new capability in a key comparison, in order to claim calibration and measurement capability claims (CMCs). With the core capability matrix, this study falls into the "Difficult to dissolve metals/metal oxides" which will support CMC categories 8 (Metal and metal alloys), 9 (Advanced materials) and 14 (Other materials).Eleven NMIs and DIs participated in the Key Comparison CCQM-K160 Platinum Group Elements in Automotive Catalyst. Participants were requested to evaluate the mass fractions of Pt, Pd and Rh in mg/kg in an unused autocatalyst material (cordierite ceramic base). The Key Comparison Reference Values (KCRVs) and Degrees of Equivalence (DoEs) were calculated utilising the NIST Decision Tree for the measurands. The participants utilised a number of sample preparation and analytical methods including hot plate digestion, microwave digestion and sodium fusion, followed by either atomic absorption spectroscopy (AAS), inductively coupled plasma optical emission spectroscopy (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS) detection. Several calibration techniques were used, namely external calibration, standard addition, isotope dilution mass spectrometry (IDMS) and an exact matching procedure. Additionally, one participant employed instrumental neutron activation analysis (INAA) with k0 standardisation which is a direct solid analysis method. The majority of participants claimed traceability to NIST primary calibrants or their own CRMs. Furthermore, several matrix CRMs were included or spiked samples for quality control. All institutes were required to determine the dry mass fraction using the stipulated protocol.The NIST decision tree was implemented for the calculation of the KCRVs and DoEs. The participant results overall showed good agreement with the KCRV, despite the variety of dissolution procedures and measurement techniques for this highly complex matrix and challenging measurands. Successful participation in CCQM-K160 demonstrated measurement capabilities for the determination of mass fraction of Pt, Pd and Rh in the mg/kg range and will support broad scope CMC claims for a wide range of challenging matrices.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 https://www.bipm.org/kcdb/.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).

Emerging investigator series: in-depth chemical profiling of tire and artificial turf crumb rubber: aging, transformation products, and transport pathways.

Crumb rubber generated from end-of-life tires (ELTs) poses a threat to environmental and human health based on its widespread use. Of particular concern is the use of ELT crumb rubber as infill for artificial turf fields, as people are unknowingly exposed to complex mixtures of chemicals when playing on these fields. Additionally, there is concern regarding transport of rubber-related chemicals from artificial turf into the environment. However, existing knowledge does not fully elucidate the chemical profile, transformation products, and transport pathways of artificial turf crumb rubber across different ages. To address these knowledge gaps, we utilized a multi-faceted approach that consisted of targeted quantitation, chemical profiling, and suspect screening via ultra-high performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS). We collected and processed 3 tire and 11 artificial turf crumb rubber samples via solvent extraction, leaching, and a bioaccessibility-based extraction. Nineteen rubber-derived chemicals were quantified using parallel reaction monitoring and isotope dilution techniques. In solvent extracts, the most abundant analytes were 1,3-diphenylguanidine (0.18-1200 μg g-1), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD, 0.16-720 μg g-1), 2-mercaptobenzothiazole (0.47-140 μg g-1), and benzothiazole (0.84-150 μg g-1). Chemical profiling assessed changes in sample diversity, abundance, polarity, and molecular mass. Suspect screening identified 81 compounds with different confidence levels (16 at level 1, 53 with level 2, 7 at level 3, and 5 at level 4). The formation rate of transformation products and clustering analysis results identified time-based trends in artificial turf field samples. We found that the first two years of aging may be critical for the potential environmental impact of artificial turf fields. Our analysis provides insight into the chemical complexity of artificial turf crumb rubber samples ranging from 0-14 years in age.

Inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS) with desolvating sample introduction and He collision gas for high-accuracy determination of Rh, Pd and Pt in automobile catalytic converters

A novel and selective method has been developed for high-accuracy determination of Pd, Pt and Rh in complex autocatalyst matrices using ICP-time-of-flight mass spectrometry (ICP-TOFMS).

Detection of gluten peptides in human duodenal fluids with immuno-liquid chromatography-mass spectrometry.

Gluten proteins are storage proteins in wheat that exhibit a certain resistance to gastrointestinal digestion. To explore solutions to cope with accidental ingestion of gluten in individuals suffering from gluten-related disorders, it is essential to monitor the fate of gluten peptides in biological samples, i.e., gastrointestinal juices, blood plasma or urine. In this work, we aimed at developing a mass spectrometry (MS)-based method for measuring gluten peptides in human duodenal fluids. Seven gluten peptides, including the well-documented 33-mer gluten peptide (LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF), were selected after a literature review and characterization of a gluten-containing product. Isotopically labelled peptides were used as references and a targeted liquid chromatography (LC) MS assay based on high resolution parallel reaction monitoring (PRM) was designed. Despite iterative and fine tuning of the LC-PRM-MS method, the low level of endogenous gluten peptides in human duodenal fluid samples precluded their direct detection. Thus, an initial immunoprecipitation (IP) step was included. Several antibodies were tested, and one proved reliable for the enrichment of the 33-mer gluten peptide as well as a few additional gluten peptides. Figures-of-merits of the immuno-LC-PRM-MS assay were assessed with a focus on quantification trueness and precision. We have developed an MS-based method for measuring the 33-mer gluten peptide in human duodenal fluids. Based on isotopic dilution, the method relies on the combination of IP and LC-PRM-MS analysis. Measurements were shown to be sensitive, quantitative, and reproducible.

CCQM-K161 "Anions in Seawater"

Main textAnions or nutrients in seawater are very important targets for oceanographic research and environmental monitoring of contaminations. Quantification of minor and trace anions in seawater has always been a challenge for the extremely high salinity, disparate levels of analyte and matrix ions, and even need to be measured at levels close to the detection limits of the method performance. Evidence of successful participation in formal, relevant international comparisons is needed to support calibration and measurement capability claims (CMCs) made by the national metrology institutes (NMIs) and designated institutes (DIs).The CCQM-K161 Anions in Seawater was organized by the Inorganic Analysis Working Group (IAWG) of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) to assess the abilities of the NMIs and DIs for the accurate determination of minor and trace anions in seawater. The measurands covered chloride (16 mg/g-25 mg/g), sulfate (1 mg/g-4 mg/g), bromide (30 mg/kg-100 mg/kg), nitrate (1 mg/kg-5 mg/kg) and phosphate (60 µg/kg-300 µg/kg). Twelve national metrology institutes and designated institutes participated in this key comparison. Participants were requested to evaluate the mass fractions, expressed in mg/g for chloride and sulfate, mg/kg for bromide and nitrate, and µg/kg for phosphate (as phosphorus) in a mixed natural seawater that was spiked with the phosphate. A variety of techniques including isotope dilution inductively coupled plasma mass spectrometry (IDMS), isotope dilution gas chromatography-mass spectrometry (ID-GC-MS), ion chromatography (IC), UV visible spectrophotometry (UV-Vis), flow injection analysis (FIA) was used by the participants for the determination.The NIST Decision Tree was used to assign the KCRV estimate and to calculate the degrees of equivalence of each participants following the IAWG Guidance on Using NIST Decision Tree for Comparison Reporting from 30 June 2023.Successful participation in CCQM-K161 demonstrates measurement capabilities for determination of anions in seawater. Considering the IAWG Core Capability Matrix, this material falls into the matrix challenge called 'High salts content', which corresponds to the CCQM amount-of-substance category sea water, and so will support CMCs for the anions in a mass fraction range from 60 µg/kg to 25 mg/g.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 https://www.bipm.org/kcdb/.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).

Certification and long-term stability monitoring of low-content folic acid and 5-methyltetrahydrofolate in human plasma certified reference material by isotope dilution ultra-high performance liquid chromatography/tandem mass spectrometry.

A reliable measurement of blood folate levels is necessary in the clinical field to prevent serious diseases such as cognitive impairment and neural tube defects. Herein, the certification of the low-content folic acid (FA) and 5-methyltetrahydrofolate (5-Me-THF) in human plasma certified reference material (KRISS CRM 111-01-018) was performed. A human plasma pool obtained from the Korean Red Cross was used as a CRM candidate. The certification of the human plasma CRM was performed by isotope dilution ultra-performance liquid chromatography/tandem mass spectrometry. Two-dimensional liquid chromatography was employed to confirm the validity of the analytical method for FA due to the susceptibility of FA to matrix effects because of its limited quantity. The CRM stability was evaluated at -20 °C for 2 months and at -70 °C for up to 12 months to determine the certified value of the CRM. The certified value of the CRM was (84.6 ± 4.3) ng kg-1 and (5.80 ± 0.47) μg kg-1 for FA and 5-Me-THF, respectively. The homogeneity of the CRM was 1.64% and 3.10% for FA and 5-Me-THF, respectively. Further long-term stability assessments were conducted, indicating that the CRM remains valid for at least 58 months at -70 °C for FA and 48 months for 5-Me-THF. Compared to other blood-based CRMs, this CRM has lower folate levels, making it helpful in establishing analytical methods for a broader range of folate levels.

An isotope dilution mass spectrometry overview: tips and applications for the measurement of radionuclides

A useful guide and a critical review of the applications of ID-MS to radionuclide measurement is provided.

Final report for SIM.QM-S12: supplementary comparison for trace elements in natural water

Main textThe SIM Supplementary Comparison SIM.QM-S12 for Trace Elements in Natural Water was undertaken to assess and demonstrate the analytical capabilities of national metrology institutes (NMIs) and designated institutes (DIs) of SIM members (or other regions) for the accurate determination of trace elements in natural water at µg/kg levels.Evidence of successful participation in formal, relevant international comparisons is needed to document calibration and measurement capability claims (CMCs) made by NMIs and DIs.Seventeen NMIs and DIs participated. Participants were requested to evaluate the mass fractions, expressed in µg/kg, of arsenic, cadmium, lead and antimony in a natural mineral groundwater that was spiked with the respective elements. A variety of instrumental techniques including inductively coupled plasma mass spectrometry (ICP-MS), isotope dilution ICP-MS (ID-ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), electrothermal atomic absorption spectrometry (ETAAS) and hydride generation flame atomic absorption spectrometry (HG-FAAS) were used by the participants for the determination.The NIST decision tree was used to assign the SCRV estimate for the proposed measurands and to calculate the degrees of equivalence of each national measurement standard following the IAWG Guidance on Using NIST Decision Tree for Comparison Reporting from 30 June 2023.Successful participation in SIM.QM-S12 demonstrates measurement for determination of elements in water matrices. Considering the IAWG Core Capability Matrix, this material falls into the matrix challenge called "Water/aqueous", which corresponds to the CCQM amount-of-substance category fresh water, and so will support CMCs for the metalloids and semi-metals at mass fraction levels below 50 µg/kg (As and Sb measurements) and transition elements at mass fraction levels below 50 µg/kg (except Hg) (for Cd and Pb measurements).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 https://www.bipm.org/kcdb/.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).