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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.15, #8)
Metrological traceability is a prerequisite for evaluation of measurement uncertainty
by Paul De Bièvre (pp. 437-438).
The determination of precision of qualitative measurement methods by interlaboratory experiments by Peter-Th. Wilrich (pp. 439-444).
In analogy to quantitative measurements, the precision of qualitative measurement methods can be characterised by the repeatability standard deviation and the reproducibility standard deviation of the sensitivity. In order to determine these standard deviations, the ISO 5725-2 approach is used. A simulation study and an example demonstrate the advantages of the method.
Keywords: Interlaboratory experiments; Qualitative measurements; Repeatability; Reproducibility; Sensitivity
The role of metrology communities under the WTO system: measurement science and conformity assessment procedures by Jookeun Park; Gun Woong Bahng; JongOh Choi; Jongseon Park (pp. 445-450).
Technical barrier to trade (TBT) has become one of the significant non-tariff measures with the advent of the WTO system in 1995. The key issue in TBT is that technical regulations, standards, and conformity assessment should not be used as barriers to trade. Regarding conformity assessment, the WTO/TBT Agreement recommends members to enter into negotiations for the mutual recognition of results of each other’s conformity assessment, as well as to permit participation of conformity assessment bodies located in other members. In this paper, it will be reviewed why the role of measurement science is important in terms of international effort to eliminate technical barriers to trade particularly in the area of conformity assessment.
Keywords: WTO; TBT; Conformity assessment; MRA; Metrology; Measurement science
Development of caprine liver quality control materials for trace element analysis of biological tissues by Pamela C. Kruger; Ciaran M. Geraghty; Patrick J. Parsons (pp. 451-458).
Certified reference materials (CRMs) are used in analytical chemistry for method validation studies in order to establish measurement accuracy, traceability, and long-term stability throughout repeated analyses. Quality control (QC) during routine analysis requires access to stable materials appropriate for the sample matrix being analyzed. However, it may be difficult to find representative, low-cost QC materials, especially for specific analytes in biological tissue matrices. Here, four caprine liver pools are prepared for use as internal QC materials for trace element measurements in biological tissue. Analytes of interest include essential and nonessential trace elements and the lanthanide series elements. The suitability of caprine liver to serve as a secondary reference material (RM), as well as for routine QC purposes, is demonstrated through homogeneity and stability measurements, and the acquisition of precision and uncertainty data. Traceability is established for selected analytes for which available CRMs can provide an unbroken chain of calibrations.
Keywords: ICP-MS; ETAAS; Secondary reference materials; Metals; Lanthanides; Aluminum; Mercury
Development of a proficiency testing scheme for a limited number of participants in the field of natural water analysis by Irena Pankratov; Sara Elhanany; Sharona Henig; Shunit Zaritsky; Ivan Ostapenko; Ilya Kuselman (pp. 459-466).
A proficiency testing (PT) scheme was developed for a limited number of analytical laboratories participating in the analysis of natural water in Israel. Three fit-for-intended-use reference materials (RMs) were prepared for a pilot PT from natural water: RM-blank and two in-house reference materials (IHRMs) with seven analytes fortified to achieve different levels of analyte concentrations. The measurands for the PT participants were the traceable spike values certified in the IHRMs, i.e., added mass concentrations of the analytes. The RM-blank and IHRMs were found to be homogeneous and stable over 11 days, the time necessary for the experimental part of the PT. The RMs were distributed to the PT participants as unknown test items similar to routine samples. The test results were evaluated using their deviations from the IHRM-certified values. Eight Israeli laboratories took part in the interlaboratory comparison. Individual laboratory performance and metrological compatibility of the PT results of the participants, as a local group of laboratories, were evaluated for every analyte.
Keywords: Proficiency testing; Natural water analysis; Limited number of participants; Measurement uncertainty; Metrological traceability, comparability, and compatibility
Aspects of proficiency testing studies of trace elements in environmental samples with a focus on laboratory performance by Luminita Antin; Paul Armishaw (pp. 467-471).
Four proficiency tests of environmentally significant elements in soil and water are described. The effects of sample matrix, analyte, sample preparation procedure, extraction method efficiency and instrumental technique on laboratory performance were assessed. Participants’ performance was evaluated using z scores and E n scores. One study included dried sediment and sediment digest as test samples. By testing both dried sediment and sediment digest in the same study, differences in laboratories’ results due to the extraction method or instrumental technique were evaluated. Cadmium and nickel were the elements with the most unsatisfactory z scores for dried sediment compared to sediment digest. The second study had as test samples river water and river water fortified with biosolid. For an evaluation of the efficiency of participants’ extraction method, the results reported for the analysis of river water were compared to the results for analysis of the same river water fortified with biosolid. No consensus could be found between participants’ results for Cr and Ni in this study as the extraction method employed by them produced results that were too variable. The last two studies included saline and fresh water samples. The analysis of fresh and saline water samples with similar analyte concentrations assisted laboratories in developing their methods for trace elements in saline water. For Cr, Pb and Se, the assigned values were reference values traceable to SI, measured using isotope dilution inductively coupled plasma mass spectrometry. Saline water containing low concentrations of analytes presented difficulties to some laboratories. Arsenic and selenium were the analytes most difficult to analyse in all types of environmental samples.
Keywords: Proficiency testing; Trace elements; Sample matrix; Extraction method efficiency; Instrumental technique
The possibility of using beef tallow biodiesel as a viscosity reference material by D. M. E. Santo Filho; R. G. Pereira; C. R. C. Rodrigues; A. P. F. Barbosa (pp. 473-476).
This study analyses the possibility of using beef tallow biodiesel transesterified with ethanol, provided by Universidade Federal Fluminense, as a viscosity reference material for biodiesels. The quantity viscosity was measured with capillary viscometers, according to Brazilian standards, in a temperature range between 20 °C and 40 °C for characterisation, and at 40 °C for homogeneity, in short-term stability (90 days) and long-term stability (450 days). Thirty-nine samples were stored, 9 at 45 °C, 6 at 4 °C and 24 at 20 °C. The behaviour of viscosity is analysed considering the estimated uncertainty of measurements for characterisation, homogeneity and stability. The reason to study a transesterified biofuel with ethanol lies in the fact that it is easy to produce this fluid from sugarcane in Brazil.
Keywords: Viscosity; Characterisation; Stability; Homogeneity; Beef tallow biodiesel
Failures of the global measurement system. Part 2: institutions, instruments and strategy by Gary Price (pp. 477-484).
Between 1998 and 2007, the governing body of the Treaty of the Metre conducted three strategic reviews of future global measurement needs. This critical review examines those reports with a view to determine whether or not this institution is capable of resolving the impasse, discussed in Part 1, that has existed for many decades in the manner of communicating the results of chemical measurements. Examining both the main substantial recommendation and the explicitly stated common presuppositions of the three reports leads to the regretful conclusion that the institution can neither resolve the impasse nor meet significant future global measurement needs. Therefore, the onus is on chemistry itself to consider carefully the units with which the results of chemical measurements may be communicated clearly and concisely to their users without the semantic confusions inherent in the International System (SI) of measurement units discussed in Part 1. At the larger level, the institutional failure of the Treaty to fully grasp the dynamism of 21st century science, technology and industry raises concerns for world trade and global economic coordination.
Keywords: Treaty of the metre; Chemical measurement; Strategy; Instrumentation; Mole