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1.
Numata M Yarita T Aoyagi Y Tsuda Y Yamazaki M Takatsu A Ishikawa K Chiba K Okamaoto K 《Analytical and bioanalytical chemistry》2007,387(7):2313-2323
Two marine sediment certified reference materials, NMIJ CRM 7304-a and 7305-a, have been issued by the National Metrology
Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) for the determination
of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). The raw materials of the CRMs were collected from
a bay near industrial activity in Japan. Characterization of these CRMs was conducted by NMIJ, where the sediments were analyzed
using multiple analytical methods such as pressurized liquid extraction (PLE), microwave-assisted extraction (MAE), saponification,
Soxhlet extraction, supercritical fluid extraction (SFE), and ultrasonic extraction; the target compounds were determined
by one of the primary methods of measurements, isotope dilution–mass spectrometry (ID-MS). Certified values have been provided
for 14 PCB congeners (PCB numbers 3, 15, 28, 31, 70, 101, 105, 138, 153, 170, 180, 194, 206, 209) and 4 OCPs (γ-HCH, 4,4′-DDT,
4,4′-DDE, 4,4′-DDD) in both CRMs. NMIJ CRM 7304-a has concentrations of the contaminants that are a factor of 2–15 greater
than in CRM 7305-a. Both CRMs have information values for PCB homolog concentrations determined by collaborative analysis
using a Japanese official method for determination of PCBs. The total PCB concentrations in the CRMs are approximately 920
and 86 μg kg−1 dry mass respectively.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
2.
Numata M Aoyagi Y Matsuo M Ishikawa K Hanari N Otsuka S Tsuda Y Yarita T 《Analytical and bioanalytical chemistry》2008,391(6):1985-1995
Four mineral oil certified reference materials (CRMs), NMIJ CRM 7902-a, CRM 7903-a, CRM 7904-a, and CRM 7905-a, have been
issued by the National Metrology Institute of Japan, which is part of the National Institute of Advanced Industrial Science
and Technology (NMIJ/AIST), for the determination of polychlorinated biphenyls (PCBs). The raw materials for the CRMs were
an insulation oil (CRM 7902-a and CRM 7903-a) and a fuel oil (CRM7904-a and CRM 7905-a). A solution of PCB3, PCB8, and technical
PCB products, comprising four types of Kaneclor, was added to the oil matrices. The total PCB concentrations in the PCB-fortified
oils (CRM 7902-a and CRM 7904-a) are approximately 6 mg kg−1. In addition, the mineral oils which were not fortified with PCBs were also distributed as CRMs (CRM 7903-a and CRM 7905-a).
Characterization of these CRMs was conducted by the NMIJ/AIST, where the mineral oils and the PCB solution were analyzed using
multiple analytical methods such as dimethylsulfoxide extraction, normal-phase liquid chromatography, gel permeation chromatography,
reversed-phase liquid chromatography, and chromatography using sulfoxide-bonded silica; and/or various capillary columns for
gas chromatography, and two ionization modes for mass spectrometry. The target compounds in the mineral oils and those in
the PCB solution were determined by one of the primary methods of measurement, isotope dilution–mass spectrometry (ID-MS).
Certified values have been provided for 11 PCB congeners (PCB3, 8, 28, 52, 101, 118, 138, 153, 180, 194, and 206) in the CRMs.
These CRMs have information values for PCB homologue concentrations determined by using a Japanese official method for determination
of PCBs in wastes and densities determined with an oscillational density meter. Because oil samples having arbitrary PCB concentrations
between respective property values of the PCB-fortified and nonfortified CRMs can be prepared by gravimetric mixing of the
CRM pairs, these CRMs can be used for validation of PCB analyses using various instruments which have different sensitivities.
Figure Preparation and certification processes of the mineral oil CRMs (example shown is polychlorinated biphenyls in insulation
oil, high/low concentrations)
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
We report the development of a National Institute of Metrology (NIM) hemoglobin A1c (HbA1c) certified reference material (CRM). Each CRM unit contains about 10 μL of hemoglobin. Both hemoglobin and glycated hemoglobin
were quantitatively determined by high-performance liquid chromatography (HPLC)–isotope dilution mass spectrometry (IDMS)
with synthesized VHLTPE and glycated VHLTPE as standards. The mass fraction of synthesized VHLTPE or glycated VHLTPE was also
quantitatively determined by HPLC-IDMS with NIM amino acid CRMs as standards. The homogeneity and stability of the CRMs were
examined with a commercial HbA1c analyzer based on the HPLC principle. Fifteen units were randomly selected for homogeneity examination, and statistical analysis
showed there was no inhomogeneity. Examination of the stability showed that the CRM was stable for at least 6 months at -80 °C.
Uncertainty components of the balance, amino acid purity, hydrolysis and proteolysis efficiency, method reproducibility, homogeneity,
and stability were taken into consideration for uncertainty evaluation. The certified value of NIM HbA1c CRM was expressed as the ratio of HbA1c to total hemoglobin in moles, and was (9.6 ± 1.9)% . The CRM can be used as a calibration or validation standard for clinical
diagnostics. It is expected to improve the comparability for HbA1c measurement in China. 相似文献
4.
The mass fractions of six organochlorine pesticides in a fish oil certified reference material (CRM) have been determined
using multiple methods of analysis. Fish oil was extracted from the filet of Tilapia fish collected from the River Nile, and
this CRM was recently issued by the National Institute of Standards (NIS). It can be used as natural matrix CRM for organochlorine
pesticides determination in fish and for marine environmental measurement purposes. The analytical methods used are described,
and the obtained results were combined to calculate the mass fractions of the six detected organochlorine pesticides and their
associated uncertainty values. It has been concluded that mass fractions of four pesticides are certified values. These are
1,1-(dichloroethylidene)bis[4-chlorobenzene](4,4′-DDE), 1,1-(2,2,-dichloroethylidene)bis[4-chlorobenzene] (4,4′-DDD), 1-chloro-2-[2,2,2-trichloro-1-(4-chlorophenyl)ethyl]benzene
(2,4′-DDT) and 1,1-(2,2,2-trichloroethylidene)bis[4-chlorobenzene] (4,4′-DDT). Meanwhile, mass fractions of two pesticides
were reference values. These are heptachlor and 1-chloro-2-[2,2-dichloro-1-(4-chlorophenyl)ethyl]benzene (2,4′-DDD). 相似文献
5.
G. C. Turk L. L. Yu Marc L. Salit William F. Guthrie 《Analytical and bioanalytical chemistry》2001,370(2-3):259-263
Multielement analyses of environmental reference materials have been performed using existing certified reference materials (CRMs) as calibration standards for inductively coupled plasma–mass spectrometry. The analyses have been performed using a high-performance methodology that results in comparison measurement uncertainties that are significantly less than the uncertainties of the certified values of the calibration CRM. Consequently, the determined values have uncertainties that are very nearly equivalent to the uncertainties of the calibration CRM. Several uses of this calibration transfer are proposed, including, re-certification measurements of replacement CRMs, establishing traceability of one CRM to another, and demonstrating the equivalence of two CRMs. RM 8704, a river sediment, was analyzed using SRM 2704, Buffalo River Sediment, as the calibration standard. SRM 1632c, Trace Elements in Bituminous Coal, which is a replacement for SRM 1632b, was analyzed using SRM 1632b as the standard. SRM 1635, Trace Elements in Subbituminous Coal, was also analyzed using SRM 1632b as the standard. 相似文献
6.
Progesterone is one of the steroid hormones. The hormone is especially important in preparing the uterus for the implantation
of the blastocyst and in maintaining pregnancy. Its concentration in serum is measured to determine ovarian function and to
predict early pregnancy. The progesterone concentration is also important for in-vitro fertilization and embryo-transfer outcomes.
We have established isotope dilution liquid chromatography–tandem mass spectrometry as a primary method for the measurement
of progesterone in human serum. Progesterone and its isotopic analogue, progesterone-13C2, in serum were monitored at mass transitions of m/z 315.2/109.2 and 317.2/111.2 respectively in multiple-reaction monitoring (MRM) mode with electrospray positive ionization.
For validation of the method, progesterone in a National Institute of Standards and Technology standard reference material
(NIST SRM) was measured, and the measured results were in good agreement with the reference values within the uncertainty.
On the basis of the established method, progesterone certified reference material (CRM) was developed in this work. The certified
value was (1.41 ± 0.036) μg kg−1. The repeatability of 1.1% and reproducibility of 0.14% showed that ID LC–MS–MS is a reliable and reproducible method. The
expanded uncertainty for the measurement of progesterone in the CRM was approximately 2.6% within 95% confidence limits. The
detection limit of progesterone was approximately 0.6 μg kg−1. The progesterone CRMs were distributed to representative clinical laboratories in the Republic of Korea for comparison with
the chemiluminescence immunoassay (CLIA), which is the most sensitive immunoassay method. The results from the comparison
showed quite a large bias among the participating laboratories. This implies that the CRM is a very important material for
establishment of traceability to its practical use. 相似文献
7.
J. Yoshinaga Y. Shibata T. Horiguchi M. Morita 《Accreditation and quality assurance》1997,2(3):154-156
The National Institute for Environmental Studies (NIES) recently prepared two candidate certified reference materials (CRMs)
for arsenicals to meet the growing demand for the quality assurance of arsenic speciation analysis. The NIES candidate CRM
No. 14 Brown Alga was prepared from Hijiki seaweed for the certification of inorganic arsenic content, and No. 15 Scallop was prepared from adductor muscle of scallop
for the certification of arsenobetaine content. The preparation of the candidate CRMs is briefly described. Cooperative analyses
for total arsenic content of the candidate CRMs have been underway. The preliminary speciation analysis at NIES revealed difficulty
in establishing suitable conditions for extracting arsenic species from the materials. Chromatograms of arsenic species by
a high performance liquid chromatography-inductively coupled plasma mass spectrometric detection system are presented to provide
information about arsenic species present in these candidate CRMs. 相似文献
8.
Matrix certified reference materials for environmental monitoring from the National Metrology Institute of Japan (NMIJ) 总被引:2,自引:0,他引:2
Takashi Yarita Akiko Takatsu Kazumi Inagaki Masahiko Numata Koichi Chiba Kensaku Okamoto 《Accreditation and quality assurance》2007,12(3-4):156-160
Matrix certified reference materials (CRMs) are playing an increasingly important role in environmental monitoring in Japan.
The National Metrology Institute of Japan (NMIJ)/National Institute of Advanced Industrial Science and Technology (AIST) has
been developing matrix CRMs for environmental monitoring since 2001, and has issued nine kinds of CRMs as NMIJ CRMs. The development
of the CRMs was conducted in NMIJ in cooperation with candidate material producers. The isotope dilution mass spectrometry
(IDMS) was principally adopted to give reliable certified values. Meanwhile, two or more analytical methods, whose levels
of accuracy were well evaluated, were applied to avoid any possible analytical bias. Two typical certification processes,
the certification of river water CRMs for trace element analysis and that of marine sediment CRMs for PCB and organochlorine
pesticide analysis, are outlined as examples.
Presented at -- “BERM-10” -- April 2006, Charleston, SC, USA. 相似文献
9.
U. Risse Elke Flammenkamp A. Kettrup Stefaan Vandendriessche 《Fresenius' Journal of Analytical Chemistry》1999,363(1):33-37
A Certified Reference Material (CRM) for determination of aromatic hydrocarbons in air was developed. The CRM 562 consists
of aromatic hydrocarbons sorbed on charcoal in glass tubes. Initial feasibility studies established that a homogeneous and
stable batch could be prepared. Three intercomparisons prior to the certification allowed the identification of various sources
of error. Then, a batch of about 3000 tubes was charged and certified on the basis of analyses carried out in 15 European
laboratories. The preparation of the reference material and the results of the certification exercise is described. An overview
on the analytical techniques used and the quality control guidelines are also presented. The certified values are 15.0 ± 0.4
μg benzene, 147.3 ± 3.8 μg toluene, 96.4 ± 2.5 μg m-xylene and 93.0 ± 2.9 μg o-xylene per tube. This reference material is
recommended for quality control of measurements in the field of occupational hygiene.
Received: 12 May 1998 / Revised: 28 August 1998 / Accepted: 1 September 1998 相似文献
10.
Linsinger TP Gawlik BM Trapmann S Lamberty A Emons H 《Analytical and bioanalytical chemistry》2004,378(5):1168-1174
Over the years, the nature of CRMs has changed considerably. Recently, more and more CRMs have been certified in their "natural" form, that is processed as little as possible, with analytes at their natural concentration level. This and the trend towards certified properties other than the concentrations of clearly defined molecules/elements have made guaranteeing stability of CRMs and estimating a shelf life an even more important issue for reference material producers than it has been before. One way to meet this challenge is to take more care in processing, storage and dispatch of CRMs. At IRMM, approximately 20 % of the RMs are stored at –20 °C or below and about 10% require cooled transportation. In addition, increased efforts for assessing stability are needed. Shelf lives are estimated using addition of an uncertainty component based on real-temperature stability studies rather than by accelerated stability studies. These pre-certification efforts are complemented by a stability-monitoring program, which at IRMM includes 80 % of the non-nuclear and non-isotopic materials. Although the costs for these efforts are high in absolute terms, they are only a minor and indispensable contribution to the total costs of CRM production. 相似文献
11.
Sheila Alves Margarida Maria Correia dos Santos Maria Ascensão Trancoso 《Accreditation and quality assurance》2009,14(2):87-93
In this work estimation of measurement uncertainties associated with the total metal content in soils was done by an intralaboratory
approach based on method validation and quality control data, and using two certified reference materials (CRM). CRM and soil
samples were analyzed following procedures based on the methods that are applied to silicate materials. All elements were
determined by atomic absorption spectrometry following a quality assurance program previously established. Quality control
actions were implemented in order to provide reliable data. The precision under within-laboratory reproducibility conditions
was estimated from triplicate analysis. The trueness component was determined as recovery of the analyte from CRMs: soil sample,
SO-2 and river clay sediment, LGC 6139. Combined measurement uncertainty was expressed in terms of precision and recovery
uncertainties and the later further split on CRM replicate analysis and uncertainty of the certified value components. The
results obtained are critically discussed on the basis of the different contributions. For the selection of the reference
material, the CRM dependent terms are critically compared in order to fulfill specific requirements.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
McCarron P Emteborg H Nulty C Rundberget T Loader JI Teipel K Miles CO Quilliam MA Hess P 《Analytical and bioanalytical chemistry》2011,400(3):821-833
The development of multi-analyte methods for lipophilic shellfish toxins based on liquid chromatography–mass spectrometry
permits rapid screening and analysis of samples for a wide variety of toxins in a single run. Validated methods and appropriate
certified reference materials (CRMs) are required to ensure accuracy of results. CRMs are essential for accurate instrument
calibration, for assessing the complete analytical method from sample extraction to data analysis and for verifying trueness.
However, CRMs have hitherto only been available for single toxin groups. Production of a CRM containing six major toxin groups
was achieved through an international collaboration. Preparation of this material, CRM-FDMT1, drew on information from earlier
studies as well as improved methods for isolation of toxins, handling bulk tissues and production of reference materials.
Previous investigations of stabilisation techniques indicated freeze-drying to be a suitable procedure for preparation of
shellfish toxin reference materials and applicable to a wide range of toxins. CRM-FDMT1 was initially prepared as a bulk wet
tissue homogenate containing domoic acid, okadaic acid, dinophysistoxins, azaspiracids, pectenotoxin-2, yessotoxin and 13-desmethylspirolide
C. The homogenate was then freeze-dried, milled and bottled in aliquots suitable for distribution and analysis. The moisture
content and particle size distribution were measured, and determined to be appropriate. A preliminary toxin analysis of the
final material showed a comprehensive toxin profile. 相似文献
13.
K. Ishikawa N. Hanari Y. Shimizu T. Ihara T. Maeda A. Nomura T. Yarita K. Kato K. Chiba 《Accreditation and quality assurance》2008,13(7):397-408
Certified reference materials (CRMs) are playing an increasingly important role in environmental monitoring in Japan. The
National Metrology Institute of Japan (NMIJ)/National Institute of Advanced Industrial Science and Technology (AIST) has been
developing CRMs of organic calibration solutions since 2003, and has issued several NMIJ CRMs. The development of these materials
was conducted at the NMIJ in cooperation with candidate material producers. The freezing-point depression method was principally
adopted for assessment of the purity of starting materials to give reliable certified values. Gas chromatography with flame
ionization detection (GC–FID) and/or high-performance liquid chromatography (HPLC), which are based on independent principles
and whose levels of accuracy are well evaluated, were applied in combination with other methods to avoid any possible analytical
bias. Purity assessment is outlined for two typical examples, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DDD) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DDT), which were used as starting materials for a CRM under development. Methods adopted for gravimetric preparation and
ampouling of solutions were qualified and optimized to reduce the uncertainties of certified values due to these factors.
Furthermore, a new experimental scheme for assessment of stability and preparation variation is proposed for the proper estimation
of uncertainties.
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
14.
Development and certification of the new NIES CRM 28: urban aerosols for the determination of multielements 总被引:1,自引:0,他引:1
Mori I Sun Z Ukachi M Nagano K McLeod CW Cox AG Nishikawa M 《Analytical and bioanalytical chemistry》2008,391(6):1997-2003
A new environmental certified reference material (CRM) for the determination of multielements in aerosol particulate matter
has been developed and certified by the National Institute for Environmental Studies (NIES), Japan, based on analyses by a
network of laboratories using a wide range of methods. The origin of the material was atmospheric particulate matter collected
on filters in a central ventilating system in a building in Beijing city centre. The homogeneity and stability of this material
were sufficient for its use as a reference material. Values for elemental mass fractions in the material were statistically
determined based on the analytical results of the participating laboratories. Eighteen certified values and 14 reference values
were obtained. The diameters, obtained from a micrographic image using image analysis software, of 99% of the particles were
less than 10 μm, demonstrating that almost all the particles in the material could be classified as particles of 10 μm or
less in aerodynamic diameter. The chemical composition and particle size distribution of this material were close to those
of an authentic aerosol collected in Beijing. NIES CRM 28 is appropriate for use in analytical quality control and in the
evaluation of methods used in the analysis of aerosols, particularly those collected in urban environments in northeast Asia
Figure New NIES CRM 28 Urban Aerosols and photo micrograph of the material 相似文献
15.
G C Turk L L Yu M L Salit W F Guthrie 《Fresenius' Journal of Analytical Chemistry》2001,370(2-3):259-263
Multielement analyses of environmental reference materials have been performed using existing certified reference materials (CRMs) as calibration standards for inductively coupled plasma-mass spectrometry. The analyses have been performed using a high-performance methodology that results in comparison measurement uncertainties that are significantly less than the uncertainties of the certified values of the calibration CRM. Consequently, the determined values have uncertainties that are very nearly equivalent to the uncertainties of the calibration CRM. Several uses of this calibration transfer are proposed, including, re-certification measurements of replacement CRMs, establishing traceability of one CRM to another, and demonstrating the equivalence of two CRMs. RM 8704, a river sediment, was analyzed using SRM 2704, Buffalo River Sediment, as the calibration standard. SRM 1632c, Trace Elements in Bituminous Coal, which is a replacement for SRM 1632b, was analyzed using SRM 1632b as the standard. SRM 1635, Trace Elements in Subbituminous Coal, was also analyzed using SRM 1632b as the standard. 相似文献
16.
M. Mironiuk M. Barańska K. Chojnacka H. Górecki 《Accreditation and quality assurance》2016,21(6):409-415
Ensuring a traceability and meaningful of a measurements is one of the most important stages of each analysis, each measurement. It is especially important for measurement of the environmental samples, like soil, which is a very complex matrix. A certified reference materials (CRMs) should be routinely used for this purpose. The paper discusses the procedure for preparation of the soil samples for certification as CRM. As for agricultural reasons there is a growing demand for CRMs regarding a nitrogen mass fraction in the Polish soil, we prepared such a material and established the reference value with associated measurement uncertainty. Homogeneity and stability of the material were shown to be appropriate for the intended purpose. The presented approach can also be used in a process of manufacture of a laboratory reference material, which can be used for a routine quality control. 相似文献
17.
Nobuyasu Hanari Nobuyasu Itoh Keiichiro Ishikawa Ryoko Iwasawa Yoshie Aoyagi Takashi Yarita 《International journal of environmental analytical chemistry》2013,93(6):692-705
A new calibration solution reference material for the determination of perfluorooctane sulfonate anion (PFOS) and its salts has been issued as a certified reference material (CRM) by the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The purity amount-of-substance fraction of raw material potassium perfluorooctane sulfonate (K-PFOS) was evaluated based on the results obtained using the freezing point depression method, and the purity mass fraction of the raw material was calculated using the average molar mass of impurities, the molar mass of K-PFOS, and the purity amount-of-substance fraction. The certified concentration of this CRM was obtained by multiplying the dilution ratio of the raw material in a prepared solution (methanol) determined from the gravimetric blending method by the purity of the raw material. The preparation concentration of K-PFOS as a certified value of NMIJ CRM 4220-a was determined to be 9.93?mg?kg?1. In addition, the standard uncertainty of the certified value was evaluated from the purity evaluation as well as from sample inhomogeneity, instability, and preparation variation obtained from LC/MS measurements of different gravimetrically prepared solutions of the NMIJ CRM. Consequently, the expanded uncertainty was estimated to be 0.15?mg?kg?1 with a coverage factor k?=?2 corresponding to the half-width of estimated confidence interval of approximately 95%. 相似文献
18.
Certified reference material for quantification of polycyclic aromatic hydrocarbons in sediment from the National Metrology Institute of Japan 总被引:2,自引:0,他引:2
Nobuyasu Itoh Yoshie Aoyagi Akiko Takatsu Takashi Yarita 《Analytical and bioanalytical chemistry》2009,393(8):2039-2049
The National Metrology Institute of Japan has issued a certified reference material (CRM) of freshwater lake sediment for
polycyclic aromatic hydrocarbon (PAHs) analyses. The certification used three extraction techniques: pressurized liquid extraction
(PLE) with toluene, PLE with dichloromethane/ethyl acetate (1:1 by volume), and alkaline extraction (1 M KOH in methanol)
in combination with microwave-assisted extraction. Both gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/dopant-assisted
atmospheric pressure photoionization/MS (LC/DA-APPI/MS) analyses were used. Certified values are provided for 18 PAHs at 1–25 μg
kg−1 except for perylene (2.08 × 103 μg kg−1), and information values are provided for two. Since the values of PAHs in the CRM are much lower than those in other CRMs
and are comparable to those found at sites with little human influence, the CRM is suitable for PAH monitoring in sediment
and soil samples. 相似文献
19.
Michela Sega Elena Amico di Meane Francesca Rolle 《Accreditation and quality assurance》2009,14(11):601-605
Metrology in chemistry has its own features, which distinguish it from classical metrology: due to the lack of primary methods
applicable in routine measurements, metrological traceability of measurement results can be achieved by using in a proper
way suitable certified reference materials (CRMs), which can assure a direct relation to a reference. This article deals with
the activity of the Italian National Institute of Metrological Research (Istituto Nazionale di Ricerca Metrologica—I.N.Ri.M.)
on the analysis of various polychlorinated biphenyls congeners in organic solution by means of gas-chromatography coupled
with mass spectrometry. The metrological traceability approach in the quantification step is pursued via calibration solutions
prepared by gravimetrically diluting a CRM. The uncertainty for the calibration solutions was evaluated taking into account
all the relevant contributions. 相似文献
20.
Isabel Cristina Serta Fraga Jéssica Corrêa Lopes Sidney Pereira Sobral Carla Matos Ribeiro 《Accreditation and quality assurance》2013,18(2):99-104
Reliable measurement results of electrolytic conductivity (EC), in particular for low values, must be metrologically traceable and be based on a realistic measurement uncertainty budget. The use of certified reference materials (CRMs) can help to achieve this goal. This paper presents results from all stages of the certification of an EC CRM with a conductivity of 1.5 μS cm?1, including the preparation of the batch solution and the evaluation of the homogeneity and stability of the bottled CRM. An uncertainty budget is presented for the CRM, including the main contributions from each of these sources. The CRM batch remained stable within its certified uncertainty for more than 1 year. 相似文献