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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.4, #6)
Summary Report on the CITAC International Symposium on Analytical Quality Assurance for the 21st Century held at CSIRO, National Measurement Laboratory (NML)
by Alan Squirrell (pp. B259-B261).
Introduction to the ACQUAL proceedings of the 12th International Conference of the Israel Society for Quality
by Ilya Kuselman (pp. 222-222).
Estimation of uncertainties in clinical analysis by R. I. Stefan; George Emil Baiulescu; Hassan Y. Aboul-Enein; Jacobus F. van Staden (pp. 225-229).
Owing to the importance of clinical analysis for human health, it is necessary to have reliable analytical information. Considering that the reliability of analytical information is a complex function of uncertainties of the sample, method, instrumentation, and data processing, it should be observed that the maximum reliability of analytical information is obtained by minimization of uncertainty values. Applying this concept to clinical analysis, the role of spectrometric and electrometric methods is highlighted.
Keywords: Key words Uncertainty; Reliability; Clinical analysis
Stoichiometry and chemical metrology: Karl Fischer reaction by Felix Sherman; I. Kuselman (pp. 230-234).
Stoichiometry of analytical reactions is discussed as an important element of many primary methods (gravimetry, volumetry, spectrophotometry, etc.) and therefore, of chemical metrology as a whole. Variations in stoichiometry caused by non-equilibrium conditions, by changes in the reaction medium or by other factors can be a source of the dominant uncertainty component in the analytical measurement. Such a situation is illustrated with the Karl Fischer (KF) reaction which is widely used in aquametry. Two kinds of solvents used as a part of the reaction medium – alcohols and amides – are compared. The influence of the media on the stoichiometry of the reaction and, correspondingly, on the titre of the KF reagent is evaluated.
Keywords: Key words Stoichiometry; Chemical metrology; Karl Fischer reaction; Aquametry; Uncertainty of measurements
Statistical evaluation of stability data for assessing variability of an analytical method by Raphael Bar (pp. 235-239).
Stability assay results of a stable solid oral dosage form, designated Product X 5 mg, were subjected to a statistical analysis in view of evaluating the intra-team repeatability and the interval-to-interval reproducibility of the analytical method. Analysis of variance and analysis of method capability were performed on stability data obtained from tablets stored in four different packages over a two-year period. Replicate-to-replicate and period-to-period standard deviations of assay results of the active drug ingredient were found to vary among the packages and were up to 1.3 and 1.5% (% assay), thus leading to maximum differences between any two reported average results of up 4.7%. Analysis of method capability showed that up to 51% of the specification range (90–110%) is taken up by variations of the reported average stability results. This large but realistic method variability does not reflect the formation of low-level impurities (ca. 0.1%) required by regulatory agencies.
Keywords: Key words Method variability; Method capability; Anova; Drug stability
Quality control in residual solvent analysis: the static headspace gas chromatographic method by Berta Iosefzon-Kuyavskaya (pp. 240-246).
Residual solvent testing of raw materials and drug products constitutes part of a quality control programme. Static headspace gas chromatography (HS/GC) is suggested in current pharmacopoeias as a general tool for residual solvent testing. But the main obstacles to using HS/GC procedures are the absence of performance tests, suitable reference solvents and matrix standards, and reference methods. Harmonized regulations for residual solvent testing allow the use of a cumulative approach to estimate the residual solvent content in drug products. The supplier data may be appropriate. Therefore, in a quality control programme the main accent is put on the definition of specification limits (in accordance with toxicological data, and the influence of residual solvents on the physical properties and stability of the product) and supplier qualification. This paper focuses on two main problems linked to supplier qualification: system performance and matrix effect. HS/GC of a mixture containing solvents of different volatility and polarity is proposed as a performance test. The test can be done in three ways in accordance with the residual solvents characteristics, the test sample solubility and the specification levels required. The use of the test as a diagnostic tool is demonstrated and sources of uncertainty of the recovery determination are discussed.
Keywords: Key words Solvent; Static headspace gas chromatography; Performance; Recovery
Metrological estimation of sampling and sample preparation procedures as applied to analytical testing of technogenic origin raw material containing recoverable precious metal by Y. A. Karpov; L. N. Filimonov (pp. 247-252).
Different schemes of analytical testing including the sampling, sample preparation and sample analysis operations are considered as applied to a lot of raw material containing recoverable precious metal. The errors resulting from the step-by-step operations of the analytical testing are estimated. Sampling and sample preparation operations are found to be significant contributors to the total error of determination of the percentage and /or weight of a precious metal of interest in a lot. Some ways to diminish both the sampling error and the total error of the analytical testing procedure are recommended.
Keywords: Key words Analytical testing; Analytical testing error; Sampling error; Metrological estimation
Quality assurance in forensic science by S. Levy; Pinchas Bergman; Arie Frank (pp. 253-255).
Forensic examination results play an increasingly important role in bringing many criminal investigations to a successful conclusion. The quality of the results of examinations performed in forensic science laboratories has always been the concern of the individual forensic scientist. The interpretations and results are presented in court to non-experts. Therefore, it is essential to ensure and maintain the highest standards of achievements and accuracy in forensic science. Many factors are important contributors to quality assurance in forensic science. Some unique subjects affect not only the mode of inquiry but also the way in which information is presented to the court, i.e. exhibits collection and sample handling, investigation, examination techniques, report writing and court testimony.
Keywords: Key words Quality assurance; Quality control; Forensic science; Court testimony; Expert witness
The metrology of unstable measurands by Alex Lepek (pp. 256-258).
Type A statistical uncertainty in measurements is usually derived from the standard deviation of the measured data. This is correct as long as the measurand is stable over time and has a meaningful constant value. In such a case the average measurement and the standard deviations are meaningful. However, as measurement methods are refined and become more precise, we can observe that a given measurand may be unstable and change with time and the uncertainty in measurement must be redefined. This is specifically true in the metrology of time which can be measured today more precisly than any other measurand. We argue that in such a case the uncertainty in the prediction of the next measurement should be used instead of the uncertainty in measurement. Both uncertainties coincide for a stable measurand. The prediction of the next measurement is achieved by means of predictors. In this paper we describe the application of linear predictors and especially optimum linear predictors to predict in the presence of various types of instability. To illustrate the issues we use clock instabilities and clock metrology as this field is most developed. A measurand can be unstable but still predictable and thus useful. This is well known in the case of white noise about a linear drift for which the optimum predictor is a linear regression. Since the deviations from prediction of optimum prediction are of white noise, we can now use simple statistics to estimate the uncertainty of the optimum or close to optimum prediction. In this paper we present the various optimum or close to optimum linear predictors optimized for different types of instability and estimate the associated prediction uncertainties.
Keywords: Key words Prediction; Time series; Uncertainty; Instability
Fourth European Conference on Quality Management in Clinical Laboratories: "Quality [R]evolution in Clinical Laboratories",
by H. M. J. Goldschmidt; J. C. Libeer (pp. 261-262).
Federation of European Chemical Societies (FECS): Division of Analytical Chemistry (DAC)
by Lauri Niinistö; I. Bauke te Nijenhuis (pp. 267-267).