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Organochlorine Pesticides in Ginseng Root

期刊: METROLOGIA, 2019; 56 (1A)

Ginseng is one of the most important traditional herbal medicines for health care and treatment of diseases. Trading of ginseng and related products is a multi-million dollar business. Four major countries including South Korea, China, Canada and the United States are the biggest producers and account for more than 99% of the total ginseng production around the world (i.e. about 80,000 tons). The Commission Regulation of European Union sets up that the maximum residue level (MRL) for hexachlorocyclohexane (sum of alpha, beta and delta isomers, except lindane) is 0.02 mg/kg and that for lindane is 1 mg/kg in ginseng. The use of reliable methods for measurement of these organochlorine pesticides is important in safeguarding the quality of ginseng and related products and public health. The Government Laboratory, Hong Kong (GLHK) previously coordinated and completed CCQM-K95 "Mid-polarity Analytes in Food Matrix: Mid-polarity Pesticides in Tea". Two organochlorine pesticide residues,beta-endosulfan and endosulfan sulfate, were selected for analysis. It is noteworthy that participating institutes in CCQM-K95 found that wetting of test samples prior to extraction was crucial for complete extraction of the incurred analytes in the test material of dried tea. It is apparent that sample extraction is a real technical challenge in the analysis of dried plant material. Ginseng root is collected after years of cultivation. It represents a higher level of analytical challenge for the participating national metrology institutes (NMIs) and designated institutes (DIs) in measuring the incurred organochlorine pesticides in dried ginseng/ginseng root, where the pesticides have been gradually accumulated in the plant material for several years. In this regard, GLHK proposed a new APMP supplementary comparison on determination of organochlorine pesticides in ginseng root at the APMP TCQM meeting in November 2015. The supplementary comparison was further discussed at the CCQM OAWG meeting in April 2016. The Chair of APMP TCQM approved the proposed supplementary comparison for 2016/17 with a study number of APMP.QM-S11 in May 2016. To allow wider participation, a pilot study APMP.QM-P32, was run in parallel with this supplementary comparison. Evidence of successful participation in formal, relevant international comparisons is needed to document calibration and measurement capability claims (CMCs) made by national metrology institutes (NMIs) and designated institutes (DIs). Seven NMIs/DIs participated in this Supplementary Comparison APMP.QM-S11 Organochlorine pesticides in ginseng root. Participants were requested to evaluate the mass fractions, expressed in mu g/kg, of alpha-hexachlorocyclohexane (alpha-BHC, CAS No. 319-84-6) and gamma-hexachlorocyclohexane (Lindane, CAS No. 58-89-9) in a relatively complex food/plant material, termed ginseng root. The purpose of the comparison is to enable participating laboratories to demonstrate their capability in the determination of organochlorine pesticides in a relatively complex food/plant material. All participating laboratories performed wetting before extraction. Different extraction methods such as soxhlet extraction, accelerated solvent extraction, ultrasonic extraction, QuEChERS technique, shaking and vortex were used among the participants. For the instrumental analysis, all laboratories employed GC techniques for chromatographic separation and most laboratories used MS related techniques for detection and quantification. For alpha-BHC, the consensus mean was 413 mu g/kg with standard deviation of 35.3 mu g/kg from 4 participating institutes' results. For lindane, the consensus mean was 104 mu g/kg with standard deviation of 10.9 mu g/kg from 5 participating institutes' results. Successful participation in APMP.QM-S11 demonstrates the following measurement capabilities in determining mass fraction of organic compounds, with molecular mass of 100 g/mol to 500 g/mol, having low polarity pK(ow) < -2, in mass fraction range from 10 mu g/kg to 1000 mu g/kg in food/plant matrices.

JIF:3.45

Key comparison in the field of acceleration on low intensity shock sensitivity

期刊: METROLOGIA, 2019; 56 (1A)

This is the final report for CIPM key comparison CCAUV.V-K4 in the area of 'vibration' (quantity of acceleration). The aim of this comparison was to measure the voltage shock sensitivity of an accelerometer measuring chain including a standard accelerometer with a charge amplifier and the charge shock sensitivity of an accelerometer at different peak acceleration values with associated pulse durations. Nine Metrology Institutes from five RMOs have participated in the comparison with National Institute of Metrology, P.R. China as pilot lab and National Metrology Institute of Japan as co-pilot lab. For voltage shock sensitivity, all the participating laboratories provided their calibration results, which were all consistent within their declared expanded uncertainties. All participants contributed to the KCRVs calculated for six peak acceleration comparison values. For charge shock sensitivity, one participant failed to contribute to the calculation of the KCRV at 5 000 m/s(2) and two participating laboratories were not consistent within their declared expanded uncertainties at a total of five peak acceleration comparison values. Further improvements of their calibration devices and uncertainty evaluations will provide more accurate and reliable measurement results in the future.

JIF:3.45

Bilateral comparison of 1 Omega and 10 k Omega standards (ongoing BIPM key comparisons BIPM.EM-K13.a and 13.b) between the NIM (The People's Republic of China) and the BIPM

期刊: METROLOGIA, 2019; 56 (1A)

This report gives the result of a bilateral comparison of resistance between the NIM (The People's Republic of China) and the BIPM carried out at the end of 2018, beginning of 2019. Two 1 Omega and two 10 k Omega travelling standards belonging to the BIPM were used. The comparison was carried out with an 'A-B -A' pattern of measurements; the standards were measured first at the BIPM for a period of about one month, then for a period of one month at the NIM, and finally again at the BIPM. The measurand was the 4 terminal dc resistance at low power. The BIPM was the pilot laboratory, and the comparison forms part of the ongoing BIPM key comparisons BIPM.EM-K13.a (for 1 Omega) and BIPM.EM-K13.b (for 10 k Omega). The results from the NIM and the BIPM were found to be in good agreement, with a difference smaller than the relative expanded uncertainties (95% confidence, k = 2) for both 1 Omega and 10 k Omega standards. Relative differences are + 0.010 x 10(-6) for 1 Omega and 0.001 x 10(-6) for 10 k Omega with a relative expanded uncertainty of 0.034 x 10(-6) for 1 Omega and 0.032 X 10(-6) for 10 k Omega.

JIF:3.45

Assay of potassium hydrogen phthalate (CCQM-K34.2016)

期刊: METROLOGIA, 2019; 56 (1A)

The CCQM-K34.2016 key comparison for determination of the purity of potassium hydrogen phthalate was organized jointly by the inorganic analysis and electrochemical analysis working groups of CCQM to repeat CCQM-K34 for supporting CMC claims of participating metrology institutes in assaying the amount content of monoprotic weak acid. National Institute of Metrology P.R.China (NIM) acted as the coordinating laboratory of this comparison. Twelve NMIs participated in this key comparison. With the exception of one laboratory that used NaOH-titration, all participants used coulometry. In general a good overlap of results was observed, the suitability of coulometry for assay of high purity materials was demonstrated again, and some possible technical problems were highlighted. The comparison tested the capabilities and methods used for assay of high purity materials. Good result indicates good performance in assaying the purity (amount content) of solid weak acids.

JIF:3.45

APMP Key Comparison of Gauge Pressure from 0.4 MPa to 4 MPa

期刊: METROLOGIA, 2019; 56 (1A)

This report describes the results of a key comparison of pneumatic pressure standards between korea research institute of standards and science (KRISS) and national institute of metrology, china (NIM) in order to determine their degrees of equivalence at pressures in the range 0.4 mpa to 4 mpa in gauge pressure. This bilateral comparison was carried out from aug. 2012 to nov. 2012 within the framework of the asia pacific metrology programme (APMP). The pilot laboratory was kriss. The degrees of equivalence in this comparison were transferred to the corresponding cc key comparison, ccm.p-k1.c through the results of apmp.m.p-k1.c, in which kriss participated. Both of the participating institutes used pneumatic pressure balances as their pressure standards. The same piston-cylinder assembly (PCA) as one used for both pressure standards was used as a transfer standard (TS). The TS was calibrated at kriss before and after the measurement at nim. The difference was used for the characterization of TS. This reports shows that NIM results are equivalent to the CCM key comparison results within the claimed uncertainty.

JIF:3.45

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the NIM, China, and the BIPM in low-energy x-rays

期刊: METROLOGIA, 2019; 56 (1A)

A key comparison has been made between the air-kerma standards of the NIM and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement at the level of the combined standard uncertainty of 3.7 parts in 10(3). The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database.

JIF:3.45

A new type of compact gravimeter for long-term absolute gravity monitoring

期刊: METROLOGIA, 2019; 56 (2)

Long-term absolute gravity monitoring has a wide range of applications in the field of geodesy, geophysics, seismology, volcanology, hydrology, etc. The traditional method of long-term absolute gravity monitoring is realized by the combination of absolute gravimeter and relative gravimeter. Here we report on a new type of compact gravimeter based on atom interferometry used for long-term absolute gravity measurements. The long-term absolute gravity monitoring could be carried out with only a single instrument. Over the course of a month we took long-term absolute gravity measurements in a seismic station. With an interrogation time of 120ms and a repetition rate of 2 Hz, the sensitivity of our cold atom gravimeter reaches 300 mu Gal root Hz(-1) without any vibration isolation system, and the gravity residual fluctuations are within +/- 60 mu Gal.

JIF:3.45

Total evaporation technique for high-accuracy isotopic analysis of isotopically enriched molybdenum by negative thermal ionization mass spectrometry

期刊: METROLOGIA, 2019; 56 (2)

The isotopic composition of isotopically enriched materials is essential for isotope dilution mass spectrometry and calibrated mass spectrometry, which are considered to be potential primary methods/authority methods of the highest metrological quality for the analysis of elemental content or isotopic compositions. In this study, a total evaporation (TE) technique was developed for accurate determination of isotopic compositions for seven enriched molybdenum materials with the utilization of negative ion-thermal ionization mass spectrometry (NTIMS). By using La(NO3)(3) as an activator, the sample was efficiently ionized into MoO3- for NTIMS measurement. To achieve highly precise results, the oxygen isotope interference in MoO3- on Mo isotopic analysis was corrected by using the IUPAC recommended isotopic compositions for atmospheric O-2. Various sources of uncertainty to TE-NTIMS, such as measurement repeatability, oxide interference correction, and the ion loss before and after measurement were discussed with respect to the determination of their uncertainty contribution and their influence on the results. As a result, the major isotope abundance for each enriched Mo material were determined as (k = 2): x(Mo-92) = 0.974 69 +/- 11 for enriched Mo-92, x(Mo-94) = 0.920 26 +/- 11 for enriched Mo-94, x(Mo-95) = 0.965 50 +/- 20 for enriched Mo-95, x(Mo-96) = 0.967 59 +/- 12 for enriched Mo-96, x(Mo-97) = 0.942 06 +/- 13 for enriched Mo-97, x(Mo-98) = 0.984 56 +/- 11 for enriched Mo-98, and x(Mo-100) = 0.993 655 +/- 12 for enriched Mo-100, respectively. These measurement results have been compared to those determined by a multi-collector inductively coupled plasma mass spectrometry via the mathematical iteration method in our previous work. Identical major isotope-abundance values were achieved within their combined standard uncertainties, indicating that the TE technique is a powerful and alternative tool for accurate determination of the isotopic composition for isotopically enriched materials. The potential influence owing to the variations of O isotopic compositions during NTIMS measurements were also investigated by applying the 'In-run O' isotope-abundance values reported in recent literatures for O isotope interference correction. The corrected Mo isotope abundances of either the major or the minor isotopes were in good agreement with that corrected by using the IUPAC atmospheric O-2 isotopic compositions.

JIF:3.45

Refractive-index gas thermometry

期刊: METROLOGIA, 2019; 56 (3)

The principles and techniques of primary refractive-index gas thermometry (RIGT) are reviewed. Absolute primary RIGT using microwave measurements of helium-filled quasi-spherical resonators has been implemented at the temperatures of the triple points of neon, oxygen, argon and water, with relative standard uncertainties ranging from 9.1 x 10(-6) to 3.5 x 10(-5). Researchers are now also using argon-filled cylindrical microwave resonators for RIGT near ambient temperature, with relative standard uncertainties between 3.8 x 10(-5) and 4.6 x 10(-5), and conducting relative RIGT measurements on isobars at low temperatures. RIGT at optical frequencies is progressing, and has been used to perform a Boltzmann constant measurement at room temperature with a relative standard uncertainty of 1.2 x 10(-5). Uncertainty budgets from implementations of absolute primary microwave RIGT, relative primary microwave RIGT and absolute primary optical RIGT are provided.

JIF:3.45

Development and validation of a suite of standards for the purity assignment of organic compounds by quantitative NMR spectroscopy

期刊: METROLOGIA, 2019; 56 (6)

The evaluation of seven internal standard reference materials (ISRMs) to act as a ?universal? SI-traceable calibrator suite for organic compound purity determination by quantitative nuclear magnetic resonance (qNMR) spectroscopy is described. The set of compounds demonstrated to constitute such a suite are: potassium hydrogen phthalate (KHP), maleic acid (MA), 3,5-bis-trifluoromethyl benzoic acid (BTFMBA), dimethyl sulfone (DMSO2), dimethyl terephthalate (DMTP), 1,4-bis-trimethlsilyl benzene (BTMSB or BTMSB-d(4)) and perdeuterated sodium 3-trimethylsilyl-1-propanesulfonate (DSS-d(6)). The compounds were selected such that at least one ISRM should be suitable for use as the internal standard for the qNMR purity assignment of an organic compound soluble in a given deuterated solvent. They allow for the selection for use as the internal reference for quantitative integration from a set of simple, sharp NMR signals dispersed over the proton chemical shift range. Optimized conditions for acquiring qNMR spectra were developed and are described, as well as the results of an extensive series of studies validating the use of the ISRM suite to assign mass fraction values in four representative solvents (D2O, DMSO-d(6), CD3OD and CDCl3). Proper use and application of these ISRMs result in standard uncertainties in the assigned values of the analyte of interest of the order of 1?mg g(?1) in optimal cases. These materials are of particular interest for the mass fraction purity determinations by qNMR of organic compound reference materials required as analyte specific calibrators to underpin the SI-traceability of the results for routine laboratory analysis based on techniques such as gas and liquid chromatography.

JIF:3.45

Establishment of measurement traceability for peptide and protein quantification through rigorous purity assessment-a review

期刊: METROLOGIA, 2019; 56 (4)

The health of their populations and efficient health care systems are of critical importance to the economic and social well-being of nations. Accurate and comparable peptide/protein measurements are required in support of diagnosis, prognosis, monitoring and treatment of widespread diseases (e.g. diabetes). The required consistency of measurement results can be achieved by making them traceable to stated references and through the development of Reference Measurement Systems. The review mainly concentrates on the progress made in the Protein Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM-PAWG) in establishing Primary Calibration Reference Services in the emerging area of health markers such as peptides/proteins. Primary Calibration Reference Services are technical capabilities for composition assignment, commonly as the mass fraction content, of pure substances or solutions thereof. It is a core technical competency for National Measurement Institutes (NMIs). A limited number of key comparisons, foreseen by the CCQM-PAWG strategy, are discussed that enable NMIs providing measurement services in peptide/protein analysis to test and demonstrate their capabilities. In addition, the review examines the development and improvement of analytical methods and metrological models that are required to meet the needs of NMIs and associated clinical stakeholders.

JIF:3.45

Real-time free-running time scale with remote clocks on fiber-based frequency network

期刊: METROLOGIA, 2019; 56 (4)

In this paper, we propose a real-time free-running time scale based on four remote hydrogen masers. The clocks in the ensemble were scattered around Beijing, connected by urban fiber links using a novel frequency synchronization system. The remote clock ensemble prevents the time scale from potential problems caused by correlation among co-located clocks. Insofar as it is real-time, it fulfills the requirements for applications such as navigation, telecommunications and so on. The free-running time scale is updated every 1200 s, and a disturbance-resistant algorithm makes it robust to fiber link disturbances and clock malfunctions. The results of a continuous experiment over 224 d are reported. The stability of the time scale outperformed any clock in the ensemble for averaging times of more than approximately 10(4) s.

JIF:3.45

Determination of the isotopic composition of hafnium using MC-ICPMS

期刊: METROLOGIA, 2019; 56 (4)

Despite the numerous important applications of hafnium isotopes in geological science, and the advances in multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS), hafnium still lacks calibrated measurements of its isotope ratios and, in turn, isotopic abundances and atomic weight. In this study, we determined the isotopic composition of hafnium in four commercial hafnium reagents, including a commonly used hafnium standard (JMC-475) and a NRC candidate isotopic reference material (HALF-1) by MC-ICPMS. The state-of-the-art regression model with NIST SRM 989 isotopic rhenium as calibrator was used to correct instrumental isotopic fractionation without reliance on other hafnium standards, normalizing isotope ratios, or exponential mass-bias fractionation model.

JIF:3.45

Accuracy and stability evaluation of the Rb-85 atom gravimeter WAG-H5-1 at the 2017 International Comparison of Absolute Gravimeters

期刊: METROLOGIA, 2019; 56 (4)

We report on the realization and evaluation of the Rb-85 mobile atom absolute gravimeter named WAG-H5-1. With a distinctive Raman laser implementation, two new systematic errors, ac Stark shift imbalance and Raman laser chirp, are found and evaluated. The robustness of the instrument was tested during 1200 km-long transportation for the 10th International Comparison of Absolute Gravimeters at Beijing in October 2017. We acquire the degree of equivalence of 3 mu Gal after the comparison. Its performance was further assessed by comparing with an absolute gravimeter (FG5X) in Wuhan. With high mobility and environmental adaptability, the gravimeter reaches a sensitivity of 30 mu Gal (Hz)(-1/2), stability of 1 mu Gal@ 4000 s and accuracy within 10 mu Gal.

JIF:3.45

Performance of WC-C peritectic and Ru-C eutectic fixed points

期刊: METROLOGIA, 2019; 56 (5)

Two types of high-temperature fixed points (HTFPs) were evaluated by VNIIOFI, NIM, KRISS and NMIJ. WC-C peritectic point cells manufactured independently in different National Metrology Institutes (NMIs) were compared for the first time, and agreement of the melting temperatures for three high-quality cells at the level of 0.05 degrees C was demonstrated. This confirms, in conjunction with previous results that verified their long-term stability, high repeatability and reproducibility, the high potential of the WC-C cell as the highest-temperature reference point for radiation thermometry. The performance of the Ru-C eutectic fixed point was verified by evaluating Ru-C cells manufactured from 99.999% purity Ru materials from different manufacturers. These cells used considerably purer materials than those used in previous studies. New Ru-C cells were constructed from the best performing materials, and the t(90) values of these cells were measured at the four NMIs on their locally-realized ITS-90 scale. The values agreed within 0.25 degrees C among the four NMIs, and the t(90) value of Ru-C was determined to be 1953.64 degrees C with an expanded uncertainty of 0.20 degrees C. Both results confirmed that performance of WC-C and of Ru-C is comparable to or exceeds that of the HTFPs evaluated in the Consultative Committee for Thermometry's HTFP project, and both fixed points have capability as a reference fixed points to be included in the future MeP-K in terms of thermodynamic temperature T.

JIF:3.45

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