SRM Values Research Articles

Use of an Integrating Cavity Spectrometer to Easily Determine Beer SRM Color Without Filtration, Centrifugation or Numerical Correction

Quantification of beer color of craft unfiltered, hazy, seltzer, and fruited beer styles can be problematic due to turbidity and unconventional ingredients. A novel integrating cavity spectrometer (ICS), designed to eliminate the effect of light scatter by the sample was employed to determine if it was able to more accurately quantify beer color compared to a conventional scanning spectrophotometer (CSS). A CSS was employed to measure the absorbance and transmission of 15 filtered and unfiltered craft brewery beer samples to determine the SRM color value and tristimulus color values. The ICS measures absorbance with a 430 nm LED to determine the single-point SRM value for each beer. The SRM values of unfiltered or 0.2 µm filtered beer samples were compared using Bland-Altman analysis and regression fits. Filtered and very clear beers showed strong agreement between the methods and Bland-Altman analysis confirmed their equivalence, particularly for SRM <25. Using the ICS alone, filtered beer versus unfiltered beer showed highly correlated values and narrow limits of agreement, successfully negating the effects of turbidity. In conclusion, SRM determination by ICS is equivalent to standard spectrophotometer single-point methods and superior in accurately determining the SRM color of hazy beers without filtration or centrifugation.

Zinc, sulfur and cadmium isotopes and Zn/Cd ratios as indicators of the origin of the supergiant Broken Hill Pb–Zn–Ag deposit and other Broken Hill-type deposits, New South Wales, Australia

AbstractVarious genetic models have been proposed for the supergiant Proterozoic Broken Hill Pb–Zn–Ag deposit largely based on geological and geochronological evidence. Here we present Zn, Cd and S isotope compositions as well as Zn/Cd ratios of sphalerite from Broken Hill and minor Broken Hill-type deposits (Australia) to help constrain these models but focus on syngenetic and magmatic–hydrothermal processes, since epigenetic models can be rejected because the orebodies were deformed and metamorphosed by the Olarian Orogeny. Values of δ34SVCDT, δ66ZnAA-ETHand δ114CdNIST SRM 3108for sphalerite from Broken Hill range from +0.27 to +4.73 ‰, −1.15 to +0.46 ‰ and −0.48 to +0.01 ‰, respectively, while those for the smaller Broken Hill-type deposits range from −5.11 to +1.28 ‰, −0.97 to +0.10 ‰ and −1.02 to +2.59 ‰, respectively. By combining published S isotope data of sulfides from the Broken Hill district with those obtained here, the sources of sulfur via thermochemical sulfate reduction, bacterial sulfate reduction and a magmatic origin cannot be distinguished. However, when the S isotope compositions are considered along with the broad range of Cd and Zn isotope data for sphalerite, which are among the lightest and heaviest yet reported for a sulfide deposit, the isotopic datasets are consistent with low-temperature biogenic processes associated with syngenetic deposition of sulfides. Cadmium isotope compositions when coupled with Zn/Cd ratios of sphalerite have previously been used to classify Pb–Zn deposits, including low-temperature, high-temperature and exhalative ores. However, the Zn/Cd ratios of sphalerite from Broken Hill cannot be used for such classification purposes.

Sphalerite and Zinc Metal Nugget Reference Materials for In Situ Zinc Isotope Ratio Determination Using fsLA‐MC‐ICP‐MS

This study examined the micro‐homogeneity of zinc isotope composition of the NIST SRM 683 and NBS 123 reference materials using femtosecond laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (fsLA‐MC‐ICP‐MS). NIST SRM 683 and NBS 123 are homogeneous in Zn isotope composition based on numerous measurements performed on twenty chips and four mounts of sphalerite using solution nebulisation (SN)‐MC‐ICP‐MS and fsLA‐MC‐ICP‐MS. The mean δ66ZnJMC‐Lyon values of NIST SRM 683 and NBS 123 determined by SN‐MC‐ICP‐MS were 0.11 ± 0.02‰ (2 standard deviation (2s), n = 100) and 0.16 ± 0.02‰ (2s, n = 62), respectively. The mean δ66ZnJMC‐Lyon values determined by fsLA‐MC‐ICP‐MS analyses for NIST SRM 683 and NBS 123 were 0.12 ± 0.05‰ (2s, n = 200) and 0.16 ± 0.05‰ (2s, n = 212), consistent with the bulk isotope compositions within uncertainty. The in situ measurement precision for NIST SRM 683 and NBS 123 was better than 0.06‰ (2s), suggesting NIST SRM 683 and NBS 123 are suitable to serve as microanalytical reference materials for Zn isotope measurement. Zinc isotopic compositions of Zn‐rich materials were also determined using fsLA‐MC‐ICP‐MS under wet/dry plasma conditions. Their δ66ZnJMC‐Lyon values were in agreement with those obtained by SN‐MC‐ICP‐MS analysis, suggesting that fsLA‐MC‐ICP‐MS is suitable to measure Zn isotopic ratios in Zn‐rich materials. Thus, this method could potentially analyse spatially resolved Zn isotope compositions at the mineral or even sub‐mineral scale, such as to address the process of ore formation or Zn redistribution in near‐surface environments.

Trace elemental analysis of Anti-Jaundice medicinal plants of Telangana using EDXRF technique

A quantitative trace elemental concentration was evaluated in various species of medicinal plants using EDXRF-spectrometer. It is non-destructive, multi-element, and high sensitive analytical technique. EX-3600 spectrometer was used for quantitative and quantitative determination of major, minor and trace elements in chosen medicinal plants and data analysis was carried out by nEXT software. Accuracy of the present results was checked by SRM values of NIST 1515Apple leaf. Thirteen elements like, P, S, Cl, K, Ca, Mn, Fe, Cu, Zn, Se, Br, Rb and Sr were determined and their concentrations were measured. From the present results it can be observed that, the elements P, S, Cl, K and Ca were found at higher level and remaining elements were found at lower level. The result of the present study shows good agreement with in the standard values of NIST 1515. The toxic or poisonous elements such as As, Pb, Co, V and Hg were not found in present selected medicinal plants. The elemental concentration of Fe, Cu, Zn, Mn and Se were found at appreciable level. These elements are essential in metabolism and required development, improvement and progressively significant for prevention and mitigate of different diseases including hepatitis and jaundice.

Direct determination of Cr and Ni in oil samples by isotope dilution and external standard calibration using inductively coupled plasma mass spectrometry

In the present work, a method for the determination of Ni and Cr in crude oil samples and derivatives (petroleum asphalt cement (CAP) and malthene) through direct analysis of samples diluted in a mixture of organic solvents (xylene/butanol), by isotope dilution inductively coupled plasma mass spectrometry (ICP-MS), was developed. An exciting advantage of the proposed method was the addition of a polar solvent (butanol) to xylene, which has allowed the dilution of the samples, making possible the use of aqueous standards for the isotope dilution, without phase separation. For comparison, external standard calibration was carried out with organic standards and dilution in the same solvent. The spectrometer was set up and the instrumental parameters were optimized for the introduction of organic samples. Oxygen was introduced into the plasma to avoid carbon build-up at the interface. For interference correction from 40Ar12C+ over 52Cr+, the dynamic reaction cell was employed with CH4 as reaction gas. Accuracy evaluation was performed by analyzing the standard reference material NIST SRM 1084a (wear-metals in lubricant oil). The agreement between the obtained results and the SRM values were within the range of 95% to 106%. The RSDs were lower than 12% for the isotope dilution, and 10% for external standard calibration. The results obtained for Ni and Cr in crude oil and derivatives have shown that both calibration methods are statistically in agreement. Although isotope dilution is not commonly used for routine analysis, it has the potential to be. The time necessary for sample preparation could be reduced with the employment of an autodiluter, and the cost of enriched isotopes is a relative issue. The ID can also be employed as a primary method to verify the accuracy of external standard calibration methods.

Comparison of the Fatty Acid Composition of Peanut Butter by Applying Different Fat Extraction Procedures

The aim of this work was to evaluate the influence of different fat extraction procedures on the fatty acids composition (FAs) of a NIST standard reference material, peanut butter (SRM�2387). Extraction of fat was made with petroleum ether by applying six extraction procedures: Soxhlet automatic with B�chi B-811 unit: Soxhlet standard (SS); Soxhlet warm (SW); Hot extraction (HE) and Continuous flow (CF), repeated extraction with solvent (SR) and Soxhlet traditional extraction (ST), by using a Soxhlet extractor. Identification of FAMEs was based on retention time (RT) and the ratio of characteristic ions (m/z) of the reference standards F.A.M.E. Mix C4-C24 and SRM�2377. FAMEs determination was realized by using internal standards (IS) and applying relative response factors (RRFi), and without IS by applying correction factors (Fi). Determination of FAMEs was performed on a GC-MS. Triglyceride of pentadecanoic acid (TAG-IS C15:0) was used as an IS to assess the analyte losses during FAMEs preparation steps, and tricosanoic acid methyl ester (FAME-IS C23:0) was used to evaluate the analyte losses on GC injection. Values of fat content and fatty acids composition determined by the 6 extraction procedures were compared with the NIST certified values of SRM�2387. All 4 procedures of extraction made with B�chi unit B-811 were effective in fat extraction and analysis of fatty acids composition compared to standard methods. Between the experimentally determined values and the certified values there were no significant differences.

Proficiency testing for pH measurements: a 3-year evaluation

Chemical Metrology Laboratory, LIPI, organizes an annual proficiency testing (PT) scheme with pH being one of the parameters investigated. This study presents and evaluates the performance of the laboratories that participated in the pH measurement during 3 consecutive years of the PT from 2014 to 2016. The PT test items were prepared by Chemical Metrology Laboratory, LIPI, from high-purity material. The homogeneity testing and stability testing of the PT test items were performed according to ISO 13528:2005. The measured reference value was directly traceable to the pH value of SRM® 185i and 187e produced by NIST, USA, and the expanded uncertainty was calculated according to ISO GUM:2008 with a coverage factor (k = 2), at a 95 % confidence level. Individual laboratory performance was reported in terms of z-scores. In the 2014 scheme, the reference buffer solution was not provided by provider, while in the 2015 and 2016 schemes, reference buffer solutions were distributed to participants alongside the PT test items. The best performance was achieved in 2015, where more than 90 % of the reported results were assessed as satisfactory. The laboratory performance in 2015 coincided with the distribution of two traceable pH standard solutions to participants which allowed them to satisfactorily calibrate their instrumentation. In conclusion, regular PT program is an effective way of demonstrating the effectiveness of quality assurance procedures applied in participating laboratories and provides opportunity for corrective action which will benefit measurements made in the future.

Determination of the Mercury Isotopic Ratio by Cold Vapor Generation Sector Field–Inductively Coupled Plasma–Mass Spectrometry Using Lead as the Internal Standard

ABSTRACTLead was applied as an internal standard for the determination of Hg isotopic ratios. Cold vapor generation (CV) coupled with sector field–inductively coupled plasma–mass spectrometry (CV-SF-ICP-MS) was used for determination of Hg. It was effective to avoid interferences of Pb from samples while improving the sensitivity of Hg isotopic analysis by an approximate factor of 45 times higher than the aerosol mode. CV-SF-ICP-MS system was constructed and operational parameters were optimized. Research showed that the long stability of the system was limited by SF-ICP-MS and had no relationship with CV under the optimized conditions. The optimized precision of Hg isotopic ratio analysis was approximately 0.1% during 4 h. Five models were applied for the mass bias correction and the Baxter model obtained the smallest relative difference, 0.52‰. The results showed that the mean value of NIST SRM 3133 Hg isotopic ratios obtained by Pb internal standard was nearly identical with the value for Tl. The same performance was also obtained in two environmental reference materials. The results show that Pb may be used as the internal standard for determination of Hg isotopic ratio instead of Tl.

Office blood pressure measurements with oscillometric devices in adolescents: a comparison with home blood pressure

Purpose: Compare multiple in office BP measurements in adolescents using an oscillometric device with out-of-office blood pressure measurements (home blood pressure monitoring – HBPM).Materials and methods: Office measurements were performed with validated semi-automatic devices twice (3 minutes interval) in two different moments (1 week apart), with a total of four readings. These BP readings were named R1, R2, R3 and R4 (following the sequence they were performed), FDM (mean of two readings on first day) and SDM (mean of two readings on second day) and SRM (R2–R4 means). The HBPM protocol included two day-time and two evening-time measurements over 6 days.Results: A total of 1024 students between 12 and 17 years were included (mean age 14.68 years; 52.4% females). The mean systolic blood pressure (SBP) values of R2, SDM and SRM were similar to HBPM values. Regarding diastolic blood pressure (DBP) HBPM value was different than R4. High SBP and DBP correlation coefficients with HBPM values were found for R2, SDM and SRM values.Conclusion: The second office BP measurement performed with an oscilometric device in adolescents was comparable to HBPM values, suggesting that two office readings might be suitable to rule out hypertension in this age group.

The chinese version of achilles tendon total rupture score: cross-cultural adaptation, reliability and validity

BackgroundThe Achilles tendon Total Rupture Score (ATRS), which is originally developed in 2007 in Swedish, is the only patient-reported outcome measure (PROM) for specific outcome assessment of an Achilles tendon rupture.Purpose of this study is to translate and cross-culturally adapt Achilles tendon Total Rupture Score (ATRS) into simplified Chinese, and primarily evaluate the responsiveness, reliability and validity.MethodsInternational recognized guideline which was designed by Beaton was followed to make the translation of ATRS from English into simplified Chinese version (CH-ATRS). A prospective cohort study was carried out for the cross-cultural adaptation. There were 112 participants included into the study. Psychometric properties including floor and ceiling effects, Cronbach’s alpha, intraclass correlation coefficient, effect size, standard response mean, and construct validity were tested.ResultsThe mean scores of CH-ATRS are 57.42 ± 13.70. No sign of floor or ceiling effect was found of CH-ATRS. High level of internal consistency was supported by the value of Cronbach’s alpha (0.893). ICC (0.979, 95%CI: 0.984-0.993) was high to indicate the high test-retest reliability. Great responsive ness was proved with the high absolute value of ES and SRM (0.84 and 8.98, respectively). The total CH-ATRS score had very good correlation with physical function and body pain subscales of SF-36 (r = −0.758 and r = −0.694, respectively, p < 0.001), while poor correlation with vitality and role physical subscales of SF-36 (r = −0.033 and r = −0.025, respectively, p ≥ 0.05), which supported construct validity of CH-ATRS.ConclusionThis Chinese version of Achilles tendon Total Rupture Score (CH-ATRS) can be used as a reliable and valid instrument for Achilles tendon rupture assessing in Chinese-speaking population.Level of evidence II

동위원소희석 액체크로마토그래피 질량분석법에 의한 분유 내 콜레스테롤의 정량

분유 내 콜레스테롤을 정량분석하기 위한 일차분석법으로 동위원소희석 질량분석법을 개발하였다. 내부표준물질로 콜레스테롤-d₄를 사용하여 분유에 첨가하였다. 분유에 지방산과 에스테르형태로 결합되어 있는 콜레스테롤을 자유 콜레스테롤로 바꾸어주기 위해 비누화과정을 수행하였다. 비누화과정은 반응온도, 반응시간, 사용한 KOH의 농도에 따라서 최적화하였으며, 그 결과로 분유시료 0.1 g에 대해 70 &#x2103;에서 180 분 동안 8 M의 KOH 0.8 mL를 첨가하여 반응을 진행시키는 최적화조건을 확립하였다. 이와 같은 조건으로 실험을 진행하여 재현성은 0.23%, 확장불확도는 95%의 신뢰범위에서 1.9%로 추정되었다. 확립된 동위원소희석 질량분석법의 유효화를 위해 분유내에서 콜레스테롤의 인증값을 가지는 NIST SRM을 측정하였고 이 결과가 인증값과 불확도 범위내에서 일치하는 것을 확인하였다. An isotope dilution liquid chromatography tandem mass spectrometry was developed as a primary method for the quantitative analysis of cholesterol in infant formula. Cholesterol-d₄ was used as an internal standard and spiked into the infant formula sample. In order to release cholesterol out of cholesteryl ester, which is cholesterol bound to fatty acids in infant formula, saponification was carried out. Saponification conditions were optimized with heating temperature, reaction time and the concentration of KOH. The optimum conditions were as follows; heating temperature was 70 &#x2103;, reaction time was 180 min and the concentration of KOH was 0.8 mL of 8 M KOH for about 0.1 g infant formula sample. Extraction of cholesterol out of sample solution was carried out with hexane uisng liquid-liquid extraction. Chromatographic analysis was carried out using Phenomenex Kinetex C₁₈ column. Mobile phase was 0.1% acetic acid in methanol/water (v/v, 99/1) and flow rate was 0.3 mL/min. Cholesterol and cholesterol-d₄ were monitored at mass transfer m/z 369/259 and 373/263 respectively. Reproducibility of the method was evaluated to be 0.23% of the measurement result. The expanded uncertainty of the measurement result of cholesterol in infant formula was approximately 1.9% at a 95% confidence level. NIST standard reference material having certified values of cholesterol in infant formula, was analyzed in order to verify this method. The ID-LC/MS/MS results were well agreed with the certified values of NIST SRM within the uncertainty.

Choice of Nonionic Surfactant Used to Formulate Type IIIA Self-Emulsifying Drug Delivery Systems and the Physicochemical Properties of the Drug Have a Pronounced Influence on the Degree of Drug Supersaturation that Develops During In Vitro Digestion

The performance of self-emulsifying drug delivery systems (SEDDS) is influenced by their tendency to generate supersaturated systems during dispersion and digestion in the gastrointestinal tract. This study investigated the effect of drug loading on supersaturation during digestion of fenofibrate or danazol SEDDS, each formulated using long-chain lipids and a range of nonionic surfactants. Supersaturation was described by the maximum supersaturation ratio (SRM) produced by in vitro digestion. This parameter was calculated as the ratio of the total concentration of drug present in the digestion vessel versus the drug solubility in the colloidal phases formed by digestion of the SEDDS. SRM proved to be a remarkable indicator of performance across a range of lipid-based formulations. SEDDS containing danazol showed little evidence of precipitation on digestion, even at drug loads approaching saturation in the formulation. In contrast, fenofibrate crystallized extensively on digestion of the corresponding series of SEDDS, depending on the drug loading. The difference was explained by the generation of higher SRM values by fenofibrate formulations. A threshold SRM of 2.5–2.6 was identified in six of the seven SEDDS. This is not a definitive threshold for precipitation, but in general when SRM is greater than 3, fenofibrate supersaturation could not be maintained. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:1050–1063, 2014

Development and Validation of Primary Method for the Determination of Glucose in Human Serum by Isotope Dilution Liquid Chromatography Tandem Mass Spectrometry and Comparison with Field Methods

Glucose is a common medical analyte measuring in human serum or blood samples. The development of a primary method is necessary for the establishment of traceability in measurements. We have developed an isotope dilution liquid chromatography tandem mass spectrometry as a primary method for the measurement of glucose in human serum. Glucose and glucose-<TEX>$^{13}C_6$</TEX> in sample were ionized in ESI negative mode and monitored at mass transfers of m/z 179/89 and 185/92 in MRM, respectively. Glucose was separated on <TEX>$NH_2P$</TEX>-50 2D column, and the mobile phase was 20 mM <TEX>$NH_4OAc$</TEX> in 30% acetonitrile/70% water. Verification of this method was performed by the comparison with NIST SRMs. Our results agreed well with the SRM values. We have developed two levels of glucose serum certified reference material using this method and distributed them to the clinical laboratories in Korea as samples for proficiency testings. The expended uncertainty was about 1.2% on 95% confidence level. In proficiency testings, the results obtained from the clinical laboratories showed about 3.6% and 3.9% RSD to the certified values. Primary method can provide the traceability to the field laboratories through proficiency testings or certified reference materials.

Field confirmation of modified pressurized solvent extraction vessels for the analysis of polychlorinated biphenyl congeners in blood samples from Great Lakes Mallards (Anas platyrhynchos)

Miniaturized pressurized solvent extraction vessels were used to examine polychlorinated biphenyl congener (PCB) concentrations in 0.2 g sample sizes of whole blood, liver, heart and breast tissue sampled from twelve Great Lakes Mallard ducks (Anas platyrhynchos). This study successfully supported the blood extraction method, previously validated only using laboratory prepared blood samples, using field samples. In situ clean-up offered excellent sample throughput without degradation of GC-MS performance; using this method, extraction, instrument analysis and data interpretation for 100 samples could be accomplished within a one to two week time period. Results indicated contamination in the blood (∑PCB = 1.9-13 ng g(-1) ww), liver (∑PCB = 0.8-11 ng g(-1) ww), breast (∑PCB = <0.1-9 ng g(-1) ww) and heart tissue (∑PCB = <0.1-6 ng g(-1) ww). Quality control included the analysis of blank samples, NIST SRM 1589a and a duplicate of each sample type (blood or tissue). All blank samples were below the method detection limit, SRM values were within 70% of their certified values and duplicates were within 70% of each other. Correlations were examined for the suite of analysed congeners between blood and various tissues; within select individuals a strong and significant correlation was observed. TEQs were calculated and compared against known toxicity data for bird species. Based on the PCB levels found in this study, no adverse health effects are expected in the birds themselves. ∑PCB concentrations in the breast tissue were also compared against both the Canadian and American guidelines for the consumption of edible poultry and based on these values, the Mallards used in this research would be safe for human consumption.

Extraction and Determination of Boron Isotopic Composition in Tourmalines

Tourmaline is an abundant boron-rich alumosilicate mineral with complex chemistry and rich in Fe, Mg, Al, Si elements. In this study, tourmaline samples were decomposed by alkali fusion method, and then the boron was separated and purified using three different procedures. It was found that both Fe3+ and Al3+ ions, rich in tourmaline samples seriously, which affected the accurate determination of boron concentration by Azomethine-H spectrophotometric method and also caused a loss of boron by specific adsorption when large amount of amorphous hydroxide precipitate formed in ion-exchange columns. The addition of small amount of EDTA can eliminate the influence, but brings serious isobaric interference on boron isotopic analysis by TIMS. Finally, a three-column ion-exchange procedure was established including the first mixed resin column, the peristaltic pump coupled boron specific resin column, and the second mixed resin column, which ensures the full recovery of boron (> 99%) from tourmaline samples with complex matrices. The PTIMS-Cs2BO2+-static double-collection method was established by selecting H3-H4 Faraday cups and optimizing parameters in Zoom Optics (Focus Quad: 15; Dispersion Quad: −85) in a Triton TI mass spectrometer. The determined average 11B/10B value of NIST SRM 951 standard boron solution was 4.05044±0.00012 (2σ, n = 8, 1 μg B), which was superior to the dynamic collection method in internal/external precision. A δ11B value of −0.3% for NIST SRM 951 through the same pretreatment procedure was obtained, indicating that there was no isotopic fractionation occurred during the extraction procedure. The comparison of boron isotopic compositions in natural samples by TIMS and MC-ICP-MS after the chemistry procedure indicated that δ11B values determined by the static PTIMS-Cs2BO2+ method were in good agreement with that by MC-ICP-MS.

Combination of developed in-house method and application of Eichrom Sr resin to determine the radioactivity of 90Sr in environmental sample

A method is described for the determination of 90Sr in environmental samples using combination of developed in-house method, Eichrom Sr resin and Beta Counter. Strontium was efficiently, rapidly and simply separated from Ca and other interfering matrix components by Eichrom Sr resin. All the results in general showed good accuracy, high precision, reliable and in good agreement between these two measured and certified value of SRM (i.e. IAEA-375, IAEA-326, IAEA-152 and IAEA-414). As a whole, the procedure described in this work notably improves conventional methods in particular concerning the time needed, sample volume, safer and others. Thus, the introduced method was successfully performed and will be applied to actual sample for the determination of 90Sr in different environmental materials such as soil, sediments, milk, biological sample, water etc.

The h index research output measurement: Two approaches to enhance its accuracy

The h index is a widely used indicator to quantify an individual's scientific research output. But it has been criticized for its insufficient accuracy—the ability to discriminate reliably between meaningful amounts of research output. As a single measure it cannot capture the complete information on the citation distribution over a scientist's publication list. An extensive data set with bibliometric data on scientists working in the field of molecular biology is taken as an example to introduce two approaches providing additional information to the h index: (1) h 2 lower, h 2 center, and h 2 upper are proposed, which allow quantification of three areas within a scientist's citation distribution: the low impact area ( h 2 lower), the area captured by the h index ( h 2 center), and the area of publications with the highest visibility ( h 2 upper). (2) Given the existence of different areas in the citation distribution, the segmented regression model (sRM) is proposed as a method to statistically estimate the number of papers in a scientist's publication list with the highest visibility. However, such sRM values should be compared across individuals with great care.

Fit for purpose validated method for the determination of the strontium isotopic signature in mineral water samples by multi-collector inductively coupled plasma mass spectrometry

A robust method allowing the routine determination of n( 87Sr)/ n( 86Sr) with at least five significant decimal digits for large sets of mineral water samples is described. It is based on 2 consecutive chromatographic separations of Sr associated to multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) measurements. Separations are performed using commercial pre-packed columns filled with “Sr resin” to overcome isobaric interferences affecting the determination of strontium isotope ratios. The careful method validation scheme applied is described. It included investigations on all parameters influencing both chromatographic separations and MC-ICPMS measurements, and also the test on a synthetic sample made of an aliquot of the NIST SRM 987 certified reference material dispersed in a saline matrix to mimic complex samples. Correction for mass discrimination was done internally using the n( 88Sr)/ n( 86Sr) ratio. For comparing mineral waters originating from different geological backgrounds or identifying counterfeits, calculations involved the well known consensus value (1/0.1194) ± 0 as reference. The typical uncertainty budget estimated for these results was 40 ‘ppm’ relative ( k = 2). It increased to 150 ‘ppm’ ( k = 2) for the establishment of stand alone results, taking into account a relative difference of about 126 ‘ppm’ systematically observed between measured and certified values of the NIST SRM 987. In case there was suspicion of a deviation of the n( 88Sr)/ n( 86Sr) ratio (worst case scenario) our proposal was to use the NIST SRM 987 value 8.37861 ± 0.00325 ( k = 2) as reference, and assign a typical relative uncertainty budget of 300 ‘ppm’ ( k = 2). This method is thus fit for purpose and was applied to eleven French samples.

Niobium and Tantalum Concentrations in NIST SRM 610 Revisited

Niobium and Ta concentrations in MPI‐DING and USGS (BCR‐2G, BHVO‐2G, BIR‐1G) silicate rock glasses and the NIST SRM 610–614 synthetic soda‐lime glasses were determined by 193 nm ArF excimer laser ablation and quadrupole ICP‐MS. Measured Nb and Ta values of MPI‐DING glasses were found to be consistently lower than the recommended values by about 15% and 25%, respectively, if calibration was undertaken using commonly accepted values of NIST SRM 610 given by Pearce et al. Analytical precision, as given by the 1 s relative standard deviation (% RSD) was less than 10% for Nb and Ta at concentrations higher than 0.1 μg g−1. A significant negative correlation was found between logarithmic concentration and logarithmic RSD, with correlation coefficients of ‐0.94 for Nb and ‐0.96 for Ta. This trend indicates that the analytical precision follows counting statistics and thus most of the measurement uncertainty was analytical in origin and not due to chemical heterogeneities. Large differences between measured and expected Nb and Ta in glasses GOR128‐G and GOR132‐G are likely to have been caused by the high RSDs associated with their very low concentrations. However, this cannot explain the large differences between measured and expected Nb and Ta in other MPI‐DING glasses, since the differences are normally higher than RSD by a factor of 3. Count rates for Nb and Ta, normalised to Ca sensitivity, for the MPI‐DING, USGS and NIST SRM 612–614 glasses were used to construct calibration curves for determining NIST SRM 610 concentrations at crater diameters ranging from 16 (im to 60 μm. The excellent correlation between the Nb/Ca1μgg‐1 signal (Nb represents the Nb signal intensity; Ca1μg g‐1 represents the Ca sensitivity) and Nb concentration, and between the Ta/Ca1μg g‐1 signal (where Ta represents the Ta signal intensity; Ca1μg g‐1 represents the Ca sensitivity) and Ta concentration (R2= 0.9992–1.00) in the various glass matrices suggests that matrix‐dependent fractionation for Nb, Ta and Ca was insignificant under the given instrumental conditions. The results confirm that calibration reference values of Nb and Ta in NIST SRM 610 given by Pearce et al. are about 16% and 28% lower, respectively. We thus propose a revision of the preferred value for Nb from 419.4 ± 57.6 μg g−1 to 485 ± 5 μg g−1 (1 s) and for Ta from 376.6 ± 77.6 μg g−1 to 482 ± 4 μg g−1 (Is) in NIST SRM 610. Using these revised values for external calibration, most of the determined average values of MPI‐DING, USGS and NIST SRM 612–614 reference glasses agree within 3% with the calculated means of reported reference values. Bulk analysis of NIST SRM 610 by standard additions using membrane desolvation ICP‐MS gave Nb = 479 ± 6 μg g−1 (1 s) and Ta = 468 ± 7 μg g−1 (1 s), which agree with the above revised values within 3%.

A Method for the Preparation of NIST Traceable Fossil Fuel Standards with Concentrations Intermediate to SRM Values

A procedure is presented whereby the fossil fuel community may design andmix SRMs in different proportions and thereby produce in their laboratorystandards for sulfur in distillate fuel oil, residual fuel oil, and coal ofalmost any desired concentration with uncertainties that are calculable andtraceable to NIST SRM certified values. The expanded uncertainty, U, of abinary blend is always less than the U of the component with the largest uncertainty,and in some cases it is less than either of the SRM components. Because thesulfur content of all fossil fuel SRMs was certified at NIST with high accuracyand precision by isotope dilution thermal ionization mass spectrometry, inalmost all cases the total expanded uncertainties of the standards producedfrom binary mixtures are an order of magnitude smaller than the reproducibilityof current methods used in commercial laboratories. The use of this methodgives the SRM user a continuum of concentrations available for calibrantsand quality control test samples. Unlike calibrants prepared from high puritycomponents, this method enables the SRM user to create a customized seriesof calibrants in the fossil fuel matrix of interest. This should reduce oreliminate biases that result from differences in matrix composition amongstandards and unknowns.