Caffeine intake by pregnant women, adults and children can be harmful to the health of all particularly fetuses if the intake exceeds the permissible limits. Therefore, it is of fundamental importance to measure its c...Caffeine intake by pregnant women, adults and children can be harmful to the health of all particularly fetuses if the intake exceeds the permissible limits. Therefore, it is of fundamental importance to measure its concentration accurately using certified reference materials (CRMs). In the literature, no scientific details are published about the certification of caffeine standard solutions, and therefore, the present article covers this gap. A batch of caffeine solution was prepared in concentration of 1000 mg/kg and bottled. Homogeneity and stability of the candidate reference material were assessed by HPLC-UV and the results showed that the material is homogenous and stable enough. Characterization of the caffeine reference material was performed by HPLC-UV, LC-MS/MS and UV-VIS-NIR spectrophotometer in three different days and the characterization uncertainty was estimated in accordance with the requirements of ISO GUM. The certified value (999.86 ± 8.57 mg/kg) was derived as a weighted mean from the gravimetry and the three characterization methods and the certified uncertainty was calculated according to ISO Guide 35. The produced CRM is of strong interest to the food and drug analytical laboratories for the validity and credibility of their caffeine measurement results.展开更多
Natural gas (NG) is one of the most important sources of energy for industrial and domestic consumption in the present era because it is cheap and free from sulfur impurities. Therefore, accurate and precise measureme...Natural gas (NG) is one of the most important sources of energy for industrial and domestic consumption in the present era because it is cheap and free from sulfur impurities. Therefore, accurate and precise measurement of its composition is of fundamental importance for trade reasons. To improve the quality of NG gas measurements, certified reference materials (CRMs) should be used for calibration of measuring equipment in order to ensure the traceability of the measurement results to the SI units. For the traceability purpose, a multicomponent natural gas mixture was prepared gravimetrically as a reference material according to ISO 6142 from pure helium, hydrogen, n-pentane, i-pentane, n-butane, i-butane, propane, ethane, hexane, methane and nitrogen. The preparation was done in two dilution steps in 5 L aluminum cylinders. The calculated mole fractions and associated uncertainties of natural gas components were verified by a dual GC-FID/TCD system in accordance with ISO 6143 calibrated by a series of primary gas mixtures (CRMs) produced by an NMI. The results obtained by gravimetry and by GC measurements have been checked for compatibility as required by ISO 6142 and were found in very good agreement. Details of the preparation and calculation of the mole fractions and uncertainties of all gas components are explained in this article.展开更多
Caffeine intake by pregnant women, adults and children can be harmful to the health of all particularly fetuses if the intake exceeds the permissible limits. Therefore, it is of fundamental importance to measure its c...Caffeine intake by pregnant women, adults and children can be harmful to the health of all particularly fetuses if the intake exceeds the permissible limits. Therefore, it is of fundamental importance to measure its concentration accurately using certified reference materials (CRMs). In the literature, no scientific details are published about the certification of caffeine standard solutions, and therefore, the present article covers this gap. A batch of caffeine solution was prepared in concentration of 1000 mg/kg and bottled. Homogeneity and stability of the candidate reference material were assessed by HPLC-UV and the results showed that the material is homogenous and stable enough. Characterization of the caffeine reference material was performed by HPLC-UV, LC-MS/MS and UV-VIS-NIR spectrophotometer in three different days and the characterization uncertainty was estimated in accordance with the requirements of ISO GUM. The certified value (999.86 ± 8.57 mg/kg) was derived as a weighted mean from the gravimetry and the three characterization methods and the certified uncertainty was calculated according to ISO Guide 35. The produced CRM is of strong interest to the food and drug analytical laboratories for the validity and credibility of their caffeine measurement results.展开更多
In this work the performance of a screening analytical method for Energy Dispersive X-Ray Fluorescence (EDXRF) analysis in terms of accuracy and precision was evaluated through analysis of rock standard reference mate...In this work the performance of a screening analytical method for Energy Dispersive X-Ray Fluorescence (EDXRF) analysis in terms of accuracy and precision was evaluated through analysis of rock standard reference materials. The method allowed the division of elements into four groups taking into account the excitation energies and measurement conditions of the sample. Two standard reference materials were used and 15 sample replicates were prepared and analyzed, then statistics were applied to assess the precision and accuracy of analytical results. The obtained results show that major compounds or elements (SiO<sub>2</sub>, P<sub>2</sub>O<sub>5</sub>, K<sub>2</sub>O, CaO, Fe<sub>2</sub>O<sub>3</sub>, Ti) can be determined in fine powder sample with a deviation lower than 15%, and a relative standard deviation in the range (1 - 10)%. The deviation was found to be lower than 5% for major compounds such as K<sub>2</sub>O, and CaO, which suggest that the EDXRF is accurate in evaluating major elemental concentrations in rock samples. It was also found that the method seems to be more accurate and precise for major elements than for trace element investigation. This screening analytical method can be used for routine analysis with acceptable results, even though the method should be optimized to increase its precision and accuracy.展开更多
Salvianolic acid A(Sal A),a water-soluble ingredient in Danshen,has various biological activities.Sal A and its impurities have similar physical and chemical properties,as well as strong reducibility;therefore,they ar...Salvianolic acid A(Sal A),a water-soluble ingredient in Danshen,has various biological activities.Sal A and its impurities have similar physical and chemical properties,as well as strong reducibility;therefore,they are difficult to prepare and purify.In this study,high-purity Sal A was obtained by purification of sephadex chromatography and preparative chromatography.Furthermore,HPLC-DAD tandem ECD and HPLC-DAD tandem MS methods were used for non-volatile organic impurity analysis,ICP-MS method was used for non-volatile inorganic impurities and mass balance method and quantitative nuclear magnetic resonance were employed to certify the product.The structures of Sal A and its relative impurities were validated by nuclear magnetic resonance spectroscopy and mass spectrometry,and their contents were quantified as well.Following the principles of ISO Guides 34:2009 and 35:2005,a Sal A reference material was certified,covering homogeneity studies,stability studies,characterization,and uncertainty estimations.展开更多
Ti separation was achieved by ion-exchange chromatography using Bio-Rad AG 1-X8 anion-exchange and DGA resins.For high-Fe/Ti and high-Mg/Ti igneous samples,a three-column procedure was required,whereas a two-column pr...Ti separation was achieved by ion-exchange chromatography using Bio-Rad AG 1-X8 anion-exchange and DGA resins.For high-Fe/Ti and high-Mg/Ti igneous samples,a three-column procedure was required,whereas a two-column procedure was used for low-Fe/Ti and low-Mg/Ti igneous samples.The Ti isotopes were analysed by MC-ICP-MS,and instrumental mass bias was corrected using a ^(47)Ti-^(49)Ti double-spike technique.The ^(47)Ti-^(49)Ti double-spike and SRM 3162a were calibrated using SRM 979-Cr,certificated value ^(53)Cr/^(52)Crt rue=0.11339.Isobaric interference was evaluated by analysing Alfa-Ti doped with Na,Mg,Ca,and Mo,and results indicate that high concentrations of Na and Mg have no significant effect on Ti isotope analyses;however,Ca and Mo interferences lead to erroneousδ^(49/47)Ti values when Ca/Ti and Mo/Ti ratios exceed 0.01 and 0.1,respectively.Titanium isotopic compositions were determined for 12 igneous reference materials,BCR-2,BHVO-2,GBW07105,AGV-1,AGV-2,W-2,GBW07123,GBW07126,GBW07127,GBW07101,JP-1,and DTS-2b.Samples yieldδ^(49/47)Ti(‰)of−0.035±0.022,−0.038±0.031,0.031±0.022,0.059±0.038,0.044±0.037,0.000±0.015,0.154±0.044,−0.044±0.018,0.010±0.022,0.064±0.043,0.169±0.034,and−0.047±0.025(relative to OL-Ti,±2SD),respectively;of which isotopic compositions of DTS-2b,JP-1,GBW07101,GBW07105,GBW07123,GBW07126,and GBW07127 are reported for the first time.Standard Alfa-Ti was analysed repeatedly over a ten-month period,indicating a reproducibility of±0.047(2SD)forδ^(49/47)Ti,similar to the precisions obtained for geochemical reference materials.展开更多
Potala PalaceConstruction of the Potala Palace began in the mid-7th century for the Tubo King Songtsan Gambo to greet his Han wife, Princess Wencheng. It comprised 999 rooms then, plus one built atop the Red Hill, whi...Potala PalaceConstruction of the Potala Palace began in the mid-7th century for the Tubo King Songtsan Gambo to greet his Han wife, Princess Wencheng. It comprised 999 rooms then, plus one built atop the Red Hill, which, said to have 1,000 rooms, was later destroyed by thunderbolts and wars. What we see today is a structure built during the 17th century.In the mid-17th century, the White House was added to the Potala Palace, which spread along the Red Hill in Lhasa.The palace is a structure of clay, wood and stone. The palace was the residence of the Dalai Lama of various generations. Beginning with the period of the 5th Dalai Lama, major religious and political ceremonies were held there.The palace covers a total area of 360,000 square meters, with major building rising 117 meters high in 13 floors, and extends some 360 meters from east to west.From 1989 to 1994, the State earmarked some 55 million Yuan and large quantities of gold and silver to repair the palace.In December 1994, the palace found its展开更多
The American Oil Chemists’ Society(AOCS) is a volunteer-led association. AOCS develops and publishes methods of analysis for fats, oils, proteins, surfactants, and related materials according to accepted internationa...The American Oil Chemists’ Society(AOCS) is a volunteer-led association. AOCS develops and publishes methods of analysis for fats, oils, proteins, surfactants, and related materials according to accepted international standards to ensure equitable trade practices on a global scale. AOCS Official Method development has been going on for over a hundred years. The founding vision of AOCS in 1909 was "an organization designed for the development and advancement of analytical methods for cottonseed products." AOCS Official Methods are essential to world trade and are used to confirm the value of billions of pounds of oilseed-based commodities and finished products each year. In addition, AOCS conducts proficiency testing, provides certified reference materials, and collaborates with other standards developers including the International Organization for Standardization(ISO) and the Codex Alimentarius Commission. AOCS serves as a professional scientific membership organization providing current and emerging information as well as disseminating research results in oils, fats, lipids, proteins, surfactants, and related materials. Several avenues are used, especially meetings, publications, interest groups, networking opportunities, and web presence. Many scientists, experts, and others engaged in working in these fields find their professional "home" in AOCS. The AOCS Technical Leadership Committee comprises some of the most experienced AOCS members and scientists. The AOCS Technical Services department staff relies on this committee for guidance on scientific matters and for advice in prioritizing the opportunities facing AOCS.展开更多
It is widely accepted that quantitative reference materials (RM), are indispensable tools for verification of the precision and accuracy of analytical measurements. The RM can be used by food microbiology laboratories...It is widely accepted that quantitative reference materials (RM), are indispensable tools for verification of the precision and accuracy of analytical measurements. The RM can be used by food microbiology laboratories, as part of their quality assurance programmes, to achieve their quality control. In Brazil, Anvisa RDC No. 12/01 specifies the enumeration of coliforms as one of the parameters for evaluating cheese quality. The aim of this study was to produce a quantitative RM for proficiency testing (PT) for use in the testing of enumeration of coliforms in cheese matrixes. A sample of an ultra-filtered cheese with a coliforms count of <3.0 MPN/g and a total n? of viable aerobes of 1.2 × 103 CFU/g was used as the matrix to produce the RM. The ultra-filtered cheese matrix was distributed in flasks, contaminated with a specific concentration of an Escherichia coli strain and submitted to freeze-drying. Sucrose was used as the cryo-protector. The RM produced was considered sufficiently homogeneous and stable at ≤ ?70?C during the entire study period (348 days). The material was also considered sufficiently stable at 4?C for six days, but instable at 30?C and 35?C for the same period. At ?20?C the RM was sufficiently stable for 161 days. It was concluded that the material showed all the necessary requirements for a quality RM to be used as PT items and could be transported to the laboratories taking part in a PT at up to 4?C for up to 6 days, since the results indicated maintenance of the cell concentrations during this period. This is the first study to describe a methodology for producing RM containing coliforms in a cheese matrix.展开更多
Flavonoids are the most widely used in the field of the food, medicine, and cosmetic due to their pharmacological functions and biological activities, such as anti-tumor, anti-inflammatory and antioxidation. This work...Flavonoids are the most widely used in the field of the food, medicine, and cosmetic due to their pharmacological functions and biological activities, such as anti-tumor, anti-inflammatory and antioxidation. This work described the assignment of purity values to 3 flavonoids certified reference materials (CRMs) including baicalein, 5,7-dihydoxy flavones and naringenine which?were developed in this study according to the ISO Guides 34 and 35. The qualitative analysis was performed by liquid chromatography-mass spectrometry (LC-MS) and infrared spectroscopy (IR). The CRMs’ purity values were assigned based on the weighted average of quantitative nuclear magnetic resonance method and mass balance approach with high resolution liquid chromatography-VWD. All the three CRMs with following value mass fractions: baicalein at a certified purity P ± U (k = 2) of 98.8% ± 0.8%;5,7-dihydoxy flavones of 99.1% ± 0.7% and naringenine of 99.5% ± 1.0% respectively. The homogeneity of the CRMs was determined by an in-house validated liquid chromatographic method. Potential degradation during storage was also investigated and a shelf-life based on this value was established.展开更多
Inductively coupled plasma mass spectrometry(ICP-MS) has become a powerful tool for providing reliable analytical results in many laboratories around the word. In this study, the mixture of HF and HNO3 acids in high-t...Inductively coupled plasma mass spectrometry(ICP-MS) has become a powerful tool for providing reliable analytical results in many laboratories around the word. In this study, the mixture of HF and HNO3 acids in high-temperature and high-pressure closed-vessel digestion technique were used to decompose some Chinese reference materials, and thirty seven elements were determined by ICP-MS. Most of the results for Chinese soil reference materials were found to be in reasonable agreement with the reference values, except Cs, Ta, Li, Ge, Zn, Nd, Tb and Ta whose values need to be revised. Their precisions were typically lower than 5% RSD. However, the Precisions of Chinese clay reference materials, especially for GBW03102 and GBW03102a, were significantly different with reference values, probably reflecting the existence of a coarser-grained fraction(>70 μm) in samples, and the formation of fluorides in Al-rich samples during sample decomposition by using the mixture of HF and HNO3 acids. Moreover, thirty-seven trace elements covering the mass range from Li to U in four Chinese clay reference materials were firstly provided with good precision and accuracy in this study.展开更多
Lead(Pb)isotopes have been extensively employed in tracing sources of Pb and its transport pathways through the environment.However,Pb isotopic ratios in related geochemical reference materials are scarce.Here,we repo...Lead(Pb)isotopes have been extensively employed in tracing sources of Pb and its transport pathways through the environment.However,Pb isotopic ratios in related geochemical reference materials are scarce.Here,we report high-precision Pb isotopic ratios measured by Nu Plasma II MC-ICP-MS using calibrated ^(205)Tl/^(203)Tl=2.38865(NIST SRM 997)for mass discrimination correction.The long-term external precision(2SD)for NISTSRM 981 of Pb,BCR-2,and BHVO-2 are 0.31‰(n=105),0.42‰(n=11),and 0.25‰(n=5)for ^(208)Pb/ ^(206)Pb and 0.16‰,0.53‰,and 0.07‰for ^(206)Pb/ ^(207)Pb,both respectively,and their Pb isotopic ratios are in excellent agreement with the recommended values.Using this method,we report for the first time Pb isotopic compositions in shale SGR-1b(USGS);coal CLB-1(USGS);stream sediments GSD-17,-21,and-23(IGGE);soils GSS-12,-13,-14,-15,and-16(IGGE);plants GSV-1,-2,and-3(IGGE);and human hair GSH-1(IGGE).展开更多
The preparation of the human hair reference material and the steps taken to confirm its homogeneity and stability as well as its certificatipn are described. Certified values for 17 elements, which are of importance f...The preparation of the human hair reference material and the steps taken to confirm its homogeneity and stability as well as its certificatipn are described. Certified values for 17 elements, which are of importance for human health, and reference values for the other 13 elements are provided for this material.展开更多
This paper describes the quantitative determination of rare-earth elements cerium, dysprosium andnon-rare-earth element copper, lead and the homogeneity examination of these four elements in yttrium oxidereference mat...This paper describes the quantitative determination of rare-earth elements cerium, dysprosium andnon-rare-earth element copper, lead and the homogeneity examination of these four elements in yttrium oxidereference material by isotope dilution spark source mass spectrometry （ID-SSMS）. The sensitivity of the meth-od is l0<sup>-5</sup>～10<sup>-7%</sup>. The precision is better than 6%. The accuracy is better than 5%. The interferences of thespectra and the optimum amount of the spike added to the sample are discussed. The choice of the conductingmaterial for the sample electrodes is studied.展开更多
In this article, the block scheme and metrological characteristics of the State primary standard of the mass (molar) fraction and mass (molar) concentration of the component in the liquid and solid substances and mate...In this article, the block scheme and metrological characteristics of the State primary standard of the mass (molar) fraction and mass (molar) concentration of the component in the liquid and solid substances and materials based on coulometric titration GET 176-2010 are given. Primary reference materials certified by coulometric titration in the Ural Scientific and Research Institute for Metrology include eight certified reference materials (CRMs) of pure solid substances (mostly salts of sodium or potassium) and one hydrochloric acid solution CRM. The metrological characteristics of these reference materials and the scheme of their application in titrimetric analysis are shown. The expanded uncertainty of the certified value (mass fraction for the solid substances or molar concentration for the solution) is in the range from 0.018% to 0.05%. Information about two primary reference materials of high purity iron and lead nitrate certified by controlled-potential coulometry with expanded uncertainty from 0.04% to 0.07% is also given.展开更多
The aim of this study is a quality assessment of X-ray fluorescence laboratory located at the University of Khartoum. The X-ray fluorescence spectrometer system consists, a set of three 109Cd sources of an initial nom...The aim of this study is a quality assessment of X-ray fluorescence laboratory located at the University of Khartoum. The X-ray fluorescence spectrometer system consists, a set of three 109Cd sources of an initial nominal activity of 10 μCi, and Si(Li) detector Energy Dispersive XRF(EDXRF) systems. It is important to carry out this work because it has an effective contribution for a wide range of research and services. The assessment was carried out by measuring 8 NIST-2709a (soil) and 13 IAEA-155 (milk powder) standard reference material samples for repeatability examinations to test the measurement precision. The total combined standards uncertainty values for XRF lab were estimated by an error from repeatability measurements adding 2.6% for error propagation related to the method. For accuracy assessment, three standard statistic approaches were applied, i.e. the Bias %, zeta-score, and En-number. The bias of all elements for both standard materials was found to be within a deviation range from −28% to 7.8%. The results of all elements for both the zeta-score test and En-number have satisfactory results except Th (Thorium) and Zr (Zirconium) which consider as questionable results for NIST SRM 2709a and unsatisfactory results for En-number.展开更多
National Advisory Committee of Experts on Standard Reference Materials was inaugurated and its first working conference convened on September 18,2020 in Beijing.The event brought together more than 30 members and repr...National Advisory Committee of Experts on Standard Reference Materials was inaugurated and its first working conference convened on September 18,2020 in Beijing.The event brought together more than 30 members and representatives from a variety of areas closely linked with the management,development and application of standard reference materials.展开更多
文摘Caffeine intake by pregnant women, adults and children can be harmful to the health of all particularly fetuses if the intake exceeds the permissible limits. Therefore, it is of fundamental importance to measure its concentration accurately using certified reference materials (CRMs). In the literature, no scientific details are published about the certification of caffeine standard solutions, and therefore, the present article covers this gap. A batch of caffeine solution was prepared in concentration of 1000 mg/kg and bottled. Homogeneity and stability of the candidate reference material were assessed by HPLC-UV and the results showed that the material is homogenous and stable enough. Characterization of the caffeine reference material was performed by HPLC-UV, LC-MS/MS and UV-VIS-NIR spectrophotometer in three different days and the characterization uncertainty was estimated in accordance with the requirements of ISO GUM. The certified value (999.86 ± 8.57 mg/kg) was derived as a weighted mean from the gravimetry and the three characterization methods and the certified uncertainty was calculated according to ISO Guide 35. The produced CRM is of strong interest to the food and drug analytical laboratories for the validity and credibility of their caffeine measurement results.
文摘Natural gas (NG) is one of the most important sources of energy for industrial and domestic consumption in the present era because it is cheap and free from sulfur impurities. Therefore, accurate and precise measurement of its composition is of fundamental importance for trade reasons. To improve the quality of NG gas measurements, certified reference materials (CRMs) should be used for calibration of measuring equipment in order to ensure the traceability of the measurement results to the SI units. For the traceability purpose, a multicomponent natural gas mixture was prepared gravimetrically as a reference material according to ISO 6142 from pure helium, hydrogen, n-pentane, i-pentane, n-butane, i-butane, propane, ethane, hexane, methane and nitrogen. The preparation was done in two dilution steps in 5 L aluminum cylinders. The calculated mole fractions and associated uncertainties of natural gas components were verified by a dual GC-FID/TCD system in accordance with ISO 6143 calibrated by a series of primary gas mixtures (CRMs) produced by an NMI. The results obtained by gravimetry and by GC measurements have been checked for compatibility as required by ISO 6142 and were found in very good agreement. Details of the preparation and calculation of the mole fractions and uncertainties of all gas components are explained in this article.
文摘Caffeine intake by pregnant women, adults and children can be harmful to the health of all particularly fetuses if the intake exceeds the permissible limits. Therefore, it is of fundamental importance to measure its concentration accurately using certified reference materials (CRMs). In the literature, no scientific details are published about the certification of caffeine standard solutions, and therefore, the present article covers this gap. A batch of caffeine solution was prepared in concentration of 1000 mg/kg and bottled. Homogeneity and stability of the candidate reference material were assessed by HPLC-UV and the results showed that the material is homogenous and stable enough. Characterization of the caffeine reference material was performed by HPLC-UV, LC-MS/MS and UV-VIS-NIR spectrophotometer in three different days and the characterization uncertainty was estimated in accordance with the requirements of ISO GUM. The certified value (999.86 ± 8.57 mg/kg) was derived as a weighted mean from the gravimetry and the three characterization methods and the certified uncertainty was calculated according to ISO Guide 35. The produced CRM is of strong interest to the food and drug analytical laboratories for the validity and credibility of their caffeine measurement results.
文摘In this work the performance of a screening analytical method for Energy Dispersive X-Ray Fluorescence (EDXRF) analysis in terms of accuracy and precision was evaluated through analysis of rock standard reference materials. The method allowed the division of elements into four groups taking into account the excitation energies and measurement conditions of the sample. Two standard reference materials were used and 15 sample replicates were prepared and analyzed, then statistics were applied to assess the precision and accuracy of analytical results. The obtained results show that major compounds or elements (SiO<sub>2</sub>, P<sub>2</sub>O<sub>5</sub>, K<sub>2</sub>O, CaO, Fe<sub>2</sub>O<sub>3</sub>, Ti) can be determined in fine powder sample with a deviation lower than 15%, and a relative standard deviation in the range (1 - 10)%. The deviation was found to be lower than 5% for major compounds such as K<sub>2</sub>O, and CaO, which suggest that the EDXRF is accurate in evaluating major elemental concentrations in rock samples. It was also found that the method seems to be more accurate and precise for major elements than for trace element investigation. This screening analytical method can be used for routine analysis with acceptable results, even though the method should be optimized to increase its precision and accuracy.
基金The authors acknowledge National Key R&D Program of China(Grant No.2016YFC1000900)The Drug Innovation Major Project(Grant No.2018ZX09711001-001-015)should be substituted by Drug Innovation Major Project(Grant No.2018ZX09711001-003-022)CAMS Innovation Fund for Medical Sciences(Grant No.2016-I2M-3-007)for financing this work.
文摘Salvianolic acid A(Sal A),a water-soluble ingredient in Danshen,has various biological activities.Sal A and its impurities have similar physical and chemical properties,as well as strong reducibility;therefore,they are difficult to prepare and purify.In this study,high-purity Sal A was obtained by purification of sephadex chromatography and preparative chromatography.Furthermore,HPLC-DAD tandem ECD and HPLC-DAD tandem MS methods were used for non-volatile organic impurity analysis,ICP-MS method was used for non-volatile inorganic impurities and mass balance method and quantitative nuclear magnetic resonance were employed to certify the product.The structures of Sal A and its relative impurities were validated by nuclear magnetic resonance spectroscopy and mass spectrometry,and their contents were quantified as well.Following the principles of ISO Guides 34:2009 and 35:2005,a Sal A reference material was certified,covering homogeneity studies,stability studies,characterization,and uncertainty estimations.
基金financially supported by the National Natural Science Foundation of China(Project Nos.41473005,41973020,41873027)。
文摘Ti separation was achieved by ion-exchange chromatography using Bio-Rad AG 1-X8 anion-exchange and DGA resins.For high-Fe/Ti and high-Mg/Ti igneous samples,a three-column procedure was required,whereas a two-column procedure was used for low-Fe/Ti and low-Mg/Ti igneous samples.The Ti isotopes were analysed by MC-ICP-MS,and instrumental mass bias was corrected using a ^(47)Ti-^(49)Ti double-spike technique.The ^(47)Ti-^(49)Ti double-spike and SRM 3162a were calibrated using SRM 979-Cr,certificated value ^(53)Cr/^(52)Crt rue=0.11339.Isobaric interference was evaluated by analysing Alfa-Ti doped with Na,Mg,Ca,and Mo,and results indicate that high concentrations of Na and Mg have no significant effect on Ti isotope analyses;however,Ca and Mo interferences lead to erroneousδ^(49/47)Ti values when Ca/Ti and Mo/Ti ratios exceed 0.01 and 0.1,respectively.Titanium isotopic compositions were determined for 12 igneous reference materials,BCR-2,BHVO-2,GBW07105,AGV-1,AGV-2,W-2,GBW07123,GBW07126,GBW07127,GBW07101,JP-1,and DTS-2b.Samples yieldδ^(49/47)Ti(‰)of−0.035±0.022,−0.038±0.031,0.031±0.022,0.059±0.038,0.044±0.037,0.000±0.015,0.154±0.044,−0.044±0.018,0.010±0.022,0.064±0.043,0.169±0.034,and−0.047±0.025(relative to OL-Ti,±2SD),respectively;of which isotopic compositions of DTS-2b,JP-1,GBW07101,GBW07105,GBW07123,GBW07126,and GBW07127 are reported for the first time.Standard Alfa-Ti was analysed repeatedly over a ten-month period,indicating a reproducibility of±0.047(2SD)forδ^(49/47)Ti,similar to the precisions obtained for geochemical reference materials.
文摘Potala PalaceConstruction of the Potala Palace began in the mid-7th century for the Tubo King Songtsan Gambo to greet his Han wife, Princess Wencheng. It comprised 999 rooms then, plus one built atop the Red Hill, which, said to have 1,000 rooms, was later destroyed by thunderbolts and wars. What we see today is a structure built during the 17th century.In the mid-17th century, the White House was added to the Potala Palace, which spread along the Red Hill in Lhasa.The palace is a structure of clay, wood and stone. The palace was the residence of the Dalai Lama of various generations. Beginning with the period of the 5th Dalai Lama, major religious and political ceremonies were held there.The palace covers a total area of 360,000 square meters, with major building rising 117 meters high in 13 floors, and extends some 360 meters from east to west.From 1989 to 1994, the State earmarked some 55 million Yuan and large quantities of gold and silver to repair the palace.In December 1994, the palace found its
文摘The American Oil Chemists’ Society(AOCS) is a volunteer-led association. AOCS develops and publishes methods of analysis for fats, oils, proteins, surfactants, and related materials according to accepted international standards to ensure equitable trade practices on a global scale. AOCS Official Method development has been going on for over a hundred years. The founding vision of AOCS in 1909 was "an organization designed for the development and advancement of analytical methods for cottonseed products." AOCS Official Methods are essential to world trade and are used to confirm the value of billions of pounds of oilseed-based commodities and finished products each year. In addition, AOCS conducts proficiency testing, provides certified reference materials, and collaborates with other standards developers including the International Organization for Standardization(ISO) and the Codex Alimentarius Commission. AOCS serves as a professional scientific membership organization providing current and emerging information as well as disseminating research results in oils, fats, lipids, proteins, surfactants, and related materials. Several avenues are used, especially meetings, publications, interest groups, networking opportunities, and web presence. Many scientists, experts, and others engaged in working in these fields find their professional "home" in AOCS. The AOCS Technical Leadership Committee comprises some of the most experienced AOCS members and scientists. The AOCS Technical Services department staff relies on this committee for guidance on scientific matters and for advice in prioritizing the opportunities facing AOCS.
基金Conselho Nacional de Desenvolvimento Cientifico e Tecnologico(CNPq),Inovatec/Fiocruz and INCQS/Fiocruz for financial support
文摘It is widely accepted that quantitative reference materials (RM), are indispensable tools for verification of the precision and accuracy of analytical measurements. The RM can be used by food microbiology laboratories, as part of their quality assurance programmes, to achieve their quality control. In Brazil, Anvisa RDC No. 12/01 specifies the enumeration of coliforms as one of the parameters for evaluating cheese quality. The aim of this study was to produce a quantitative RM for proficiency testing (PT) for use in the testing of enumeration of coliforms in cheese matrixes. A sample of an ultra-filtered cheese with a coliforms count of <3.0 MPN/g and a total n? of viable aerobes of 1.2 × 103 CFU/g was used as the matrix to produce the RM. The ultra-filtered cheese matrix was distributed in flasks, contaminated with a specific concentration of an Escherichia coli strain and submitted to freeze-drying. Sucrose was used as the cryo-protector. The RM produced was considered sufficiently homogeneous and stable at ≤ ?70?C during the entire study period (348 days). The material was also considered sufficiently stable at 4?C for six days, but instable at 30?C and 35?C for the same period. At ?20?C the RM was sufficiently stable for 161 days. It was concluded that the material showed all the necessary requirements for a quality RM to be used as PT items and could be transported to the laboratories taking part in a PT at up to 4?C for up to 6 days, since the results indicated maintenance of the cell concentrations during this period. This is the first study to describe a methodology for producing RM containing coliforms in a cheese matrix.
文摘Flavonoids are the most widely used in the field of the food, medicine, and cosmetic due to their pharmacological functions and biological activities, such as anti-tumor, anti-inflammatory and antioxidation. This work described the assignment of purity values to 3 flavonoids certified reference materials (CRMs) including baicalein, 5,7-dihydoxy flavones and naringenine which?were developed in this study according to the ISO Guides 34 and 35. The qualitative analysis was performed by liquid chromatography-mass spectrometry (LC-MS) and infrared spectroscopy (IR). The CRMs’ purity values were assigned based on the weighted average of quantitative nuclear magnetic resonance method and mass balance approach with high resolution liquid chromatography-VWD. All the three CRMs with following value mass fractions: baicalein at a certified purity P ± U (k = 2) of 98.8% ± 0.8%;5,7-dihydoxy flavones of 99.1% ± 0.7% and naringenine of 99.5% ± 1.0% respectively. The homogeneity of the CRMs was determined by an in-house validated liquid chromatographic method. Potential degradation during storage was also investigated and a shelf-life based on this value was established.
基金supported by the National Natural Science Foundation of China (41272004)the MOST Special Funds from the State Key Laboratory of Continental Dynamics
文摘Inductively coupled plasma mass spectrometry(ICP-MS) has become a powerful tool for providing reliable analytical results in many laboratories around the word. In this study, the mixture of HF and HNO3 acids in high-temperature and high-pressure closed-vessel digestion technique were used to decompose some Chinese reference materials, and thirty seven elements were determined by ICP-MS. Most of the results for Chinese soil reference materials were found to be in reasonable agreement with the reference values, except Cs, Ta, Li, Ge, Zn, Nd, Tb and Ta whose values need to be revised. Their precisions were typically lower than 5% RSD. However, the Precisions of Chinese clay reference materials, especially for GBW03102 and GBW03102a, were significantly different with reference values, probably reflecting the existence of a coarser-grained fraction(>70 μm) in samples, and the formation of fluorides in Al-rich samples during sample decomposition by using the mixture of HF and HNO3 acids. Moreover, thirty-seven trace elements covering the mass range from Li to U in four Chinese clay reference materials were firstly provided with good precision and accuracy in this study.
基金supported by National Key Basic Research Program of China(2014CB238903)the National Natural Science Foundation of China(Nos.41473028,41673017,U1612441)the Opening Fund of State Key Laboratory of Environmental Geochemistry(SKLEG2015201)
文摘Lead(Pb)isotopes have been extensively employed in tracing sources of Pb and its transport pathways through the environment.However,Pb isotopic ratios in related geochemical reference materials are scarce.Here,we report high-precision Pb isotopic ratios measured by Nu Plasma II MC-ICP-MS using calibrated ^(205)Tl/^(203)Tl=2.38865(NIST SRM 997)for mass discrimination correction.The long-term external precision(2SD)for NISTSRM 981 of Pb,BCR-2,and BHVO-2 are 0.31‰(n=105),0.42‰(n=11),and 0.25‰(n=5)for ^(208)Pb/ ^(206)Pb and 0.16‰,0.53‰,and 0.07‰for ^(206)Pb/ ^(207)Pb,both respectively,and their Pb isotopic ratios are in excellent agreement with the recommended values.Using this method,we report for the first time Pb isotopic compositions in shale SGR-1b(USGS);coal CLB-1(USGS);stream sediments GSD-17,-21,and-23(IGGE);soils GSS-12,-13,-14,-15,and-16(IGGE);plants GSV-1,-2,and-3(IGGE);and human hair GSH-1(IGGE).
基金The Project Supported by National Natural Science Foundation of China
文摘The preparation of the human hair reference material and the steps taken to confirm its homogeneity and stability as well as its certificatipn are described. Certified values for 17 elements, which are of importance for human health, and reference values for the other 13 elements are provided for this material.
文摘This paper describes the quantitative determination of rare-earth elements cerium, dysprosium andnon-rare-earth element copper, lead and the homogeneity examination of these four elements in yttrium oxidereference material by isotope dilution spark source mass spectrometry （ID-SSMS）. The sensitivity of the meth-od is l0<sup>-5</sup>～10<sup>-7%</sup>. The precision is better than 6%. The accuracy is better than 5%. The interferences of thespectra and the optimum amount of the spike added to the sample are discussed. The choice of the conductingmaterial for the sample electrodes is studied.
文摘In this article, the block scheme and metrological characteristics of the State primary standard of the mass (molar) fraction and mass (molar) concentration of the component in the liquid and solid substances and materials based on coulometric titration GET 176-2010 are given. Primary reference materials certified by coulometric titration in the Ural Scientific and Research Institute for Metrology include eight certified reference materials (CRMs) of pure solid substances (mostly salts of sodium or potassium) and one hydrochloric acid solution CRM. The metrological characteristics of these reference materials and the scheme of their application in titrimetric analysis are shown. The expanded uncertainty of the certified value (mass fraction for the solid substances or molar concentration for the solution) is in the range from 0.018% to 0.05%. Information about two primary reference materials of high purity iron and lead nitrate certified by controlled-potential coulometry with expanded uncertainty from 0.04% to 0.07% is also given.
文摘The aim of this study is a quality assessment of X-ray fluorescence laboratory located at the University of Khartoum. The X-ray fluorescence spectrometer system consists, a set of three 109Cd sources of an initial nominal activity of 10 μCi, and Si(Li) detector Energy Dispersive XRF(EDXRF) systems. It is important to carry out this work because it has an effective contribution for a wide range of research and services. The assessment was carried out by measuring 8 NIST-2709a (soil) and 13 IAEA-155 (milk powder) standard reference material samples for repeatability examinations to test the measurement precision. The total combined standards uncertainty values for XRF lab were estimated by an error from repeatability measurements adding 2.6% for error propagation related to the method. For accuracy assessment, three standard statistic approaches were applied, i.e. the Bias %, zeta-score, and En-number. The bias of all elements for both standard materials was found to be within a deviation range from −28% to 7.8%. The results of all elements for both the zeta-score test and En-number have satisfactory results except Th (Thorium) and Zr (Zirconium) which consider as questionable results for NIST SRM 2709a and unsatisfactory results for En-number.
文摘National Advisory Committee of Experts on Standard Reference Materials was inaugurated and its first working conference convened on September 18,2020 in Beijing.The event brought together more than 30 members and representatives from a variety of areas closely linked with the management,development and application of standard reference materials.
