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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.6, #7)


CCQM primary methods symposium: how far does the light shine? by R. I. Wielgosz (pp. B329-B331).
The Consultative Committee for Amount of Substance (CCQM) has the task of organizing a comprehensive set of international comparisons to establish the technical basis for the mutual recognition of measurement capabilities among the national measurement institutes (NMIs) in the field of chemical measurement. The challenge that the CCQM faces is to identify, design, and conduct a limited number of key comparisons to enable the assessment of measurement comparability among NMIs across the entirety of ’chemical measurement space’. This is no easy task because the field of chemical metrology is extremely diverse and multidimensional, owing to the number of measurand types, concentrations, and matrix types of importance. The ”CCQM primary methods symposium: how far does the light shine?” was organized to provide information and initiate discussions to assist in this challenge, and clarify how the concept of a primary method of measurement could be instrumental in achieving this goal.

Keywords: Keywords CCQM; Primary methods; Key comparisons


Uncertainty calculations in the certification of reference materials 4. Characterisation and certification by Adriaan M. H. van der Veen; Thomas P. J. Linsinger; Heinz Schimmel; Andree Lamberty; Jean Pauwels (pp. 290-294).
The main objective of the certification of a reference material is to determine its property values including their uncertainty. In the previous parts of this series, the basis for the evaluation of measurement uncertainty of the property values has been examined, including the conversion of homogeneity and stability study data into standard uncertainties. In this final part, the determination of the property values and the modelling of the certification process is discussed. It is noted that the characterisation of a reference material can be modelled in some cases using analysis of variance statistics, but a more generally applicable model can be developed based on χ2-fitting. Furthermore, it is concluded that there is an advantage in using absolute standard uncertainties instead of relative ones when modelling the certification process.

Keywords: Keywords CRMs; Measurement uncertainty; Homogeneity study; Stability study; Certification


The practice of proficiency testing in China by G. Zhixiang; L. Ying; Tong Jian; Zang Muwen (pp. 295-296).
This paper briefly summarises the current situation for proficiency testing (PT) in China, outlines the policy for PT of China’s national accreditation committee for laboratories (CNACL), and exemplifies activities of the CNACL’s metal working group.

Keywords: Keywords China; Proficiency testing; Metal analysis; National policy


Use of calibration gases in the U.S. acid rain program by J. T. Schakenbach (pp. 297-301).
The United States Acid Rain Program continuous emission monitors (CEMs) have been successful in producing quality-assured data 95% of the time, and in meeting a relative accuracy standard of less than or equal to 10.0% at over 99% of the CEMs in the program. One key reason for this high accuracy is the required use of high quality calibration gases in certification and quality assurance/quality control (QA/QC) tests. An annual QA audit helps ensure high quality calibration gases. A third party purchases gases from gas vendors. An Environmental Protection Agency (EPA) laboratory analyzes the gases and compares the results with the tag value on the cylinder. The results are posted on an EPA website. This allows purchasers of calibration gases to buy gases from vendors producing the most accurate gases. Over time, we believe it also results in better accuracy from all gas vendors. Because of a change in SO2 quantification methodology, SO2 emissions were underreported by approximately 2% between 1989 and 1996. EPA, the National Institute for Standards and Technology and calibration gas vendors collaborated to produce a correction policy and a standard correction form to be used by affected electric utility plants. Calibration gas cylinder tag values were required to be corrected by 1 January, 1997. In the future, it is possible that cleaner, more varied sources will be regulated for greenhouse effect, ozone and toxic emissions control. This will probably require more accurate CEMs, lower calibration gas concentrations, and a broader menu of gas mixtures.

Keywords: Keywords Gas analysis; Calibration; Acid rain


Problems of traceability of total protein and catecholamine determinations in human urine by Ilona Šperlingová; Ludmila Dabrowská; Miloò Tichý; Jan Kučera (pp. 302-305).
Some problems arising in the establishment of the traceabili- ty of the certified reference materi- al (CRM) CZ 6007a (total protein, creatinine and stress indicators) are discussed. Bovine serum albumin is recommended as a calibration standard for total protein determi- nation

Keywords: Keywords Reference material; Traceability; Total protein; Stress indicators


Traceability in routine chemical measurements: an example of application in the determination of CO2 at atmospheric concentration by M. Sega; Margherita Plassa; Elena Amico di Meane (pp. 306-309).
In routine chemical measurements traceability can be achieved by using analytical instruments calibrated against primary reference materials. In the present work the calibration of a CO2 non-dispersive infrared (NDIR) analyzer with measuring range 0–2000 µmol/mol of CO2 and a resolution of 5 µmol/mol is reported. A procedure with working reference gas mixtures (WRMs) has been adopted, which requires seven calibration points. Primary reference gas mixtures (PRMs) are used to validate WRMs in a narrower range around the average atmospheric CO2 concentration value. In this range the relative uncertainty reached is of the order of some parts in 103 and the corrections are between 1 µmol/mol and 5 µmol/mol.

Keywords: Keywords Traceability; Carbon dioxide determination; Calibration; Uncertainty


Evaluation of combined measurement uncertainty of the determination of Mn content in sediment samples by József Hlavay; Klára Polyák (pp. 310-316).
Combined uncertainties of an analysis of elemental content of sediment samples were evaluated. A monitoring system has been designed and implemented for the characterization of the environmental conditions of Lake Balaton in Hungary. Sediments samples were collected and an acidic digestion method was used to determine the concentration of elements. For the calculation of the result of each measurement three different approaches were considered, namely a.) the calculation of the result using a calibration curve and estimating the confidence limit by the Student t-distribution, b.) calculation of the combined uncertainty and c.) estimation of the sampling errors using the transport and field blanks. The latter approach gave the most reliable result since it included all the parameters which had to be considered regarding sampling and sample handling, and measurement. Determination of acid soluble Mn content in sediment samples has been chosen as an example, and the combined uncertainty is calculated using blanks for sampling.

Experience with wheat flour reference material by J. Budai; Judit Fükõ (pp. 317-320).
The Chemical Section of the National Office of Measures, Hungary (OMH) [1] embarked on the preparation of a wheat sample series as a Certified Reference Material [2] (CRM) in 1992. The practical implementation of the wheat sample series has shown that test- ing laboratories are in great need of easy-to-use flour reference samples to objectively and independently qualify wheat. To fill this need, we have developed a three-term flour reference sample series. The certification process was car-ried out according to ISO recommendations. Investigations of the long-term stability [3] and the application of wheat and flour CRMs are continuing. Wheat is one of the most widely grown crops in Hun- gary and it is one of the major determinative factors in the economy. Its uniform and objective qualification is of outstanding importance. There are well-equipped laborato-ries with sufficient experience to assess wheat flour quality, howev- er, proficiency testing has shown that certified samples need to be used to achieve exact and uniform measuring results.

Keywords: Keywords Certified reference material; Reference material; Proficieny testing; Accredited laboratories; Falling numbers; Wet gluten; Water-absorbing capacity; Ash content; Protein content; Moisture content


Flow-through coulometry as a calibrationless method in inorganic trace analysis by E. Beinrohr (pp. 321-324).
The possibility of calibration-less determination of trace concentrations of some electrochemically active elements such as Ag, As, Cd, Hg, Pb, etc. by flow-through coulometry is described. The analyte species are collected quantitative-ly from the flowing sample solution on a porous working electrode made of vi- treous carbon particles set at either a constant potential or constant current. The deposit is stripped by a constant current in the next step and the correspond- ing electrical charge is measured and evaluated. The analyte concentration is calculated by making use of the com- bined Faraday’s laws of electrolysis. The method exerts detection limits about 1 µg/l or lower and a linear concentration range over 3 orders of magnitude.

Keywords: Keywords Absolute determination; Trace analysis; Flow-through coulometry


Chemical metrology in New Zealand by Marcus Krapp (pp. 324-326).
Recent developments in international trade will have a significant impact on New Zealand’s measurement infrastructure, especially for chemical metrology. This article describes the background to these developments and outlines the activities of the Measurement Standards Laboratory, New Zealand’s National Metrology Institute, in response to these developments.

Keywords: Keywords Mutual Recognition Arrangement (MRA); National Metrology Institute (NMI); Chemical metrology; Comparability; Traceability

Latest news on BCR/IRMM reference materials by Jean Pauwels (pp. 328-329).
Calendar of Events (pp. 336-338).
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