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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.13, #12)
Quality by Design applications in biosimilar pharmaceutical products by Ron S. Kenett; Dan A. Kenett (pp. 681-690).
A process is well understood when all critical sources of variability are identified and explained, variability is managed by the process design and monitoring, and product quality attributes are accurately and reliably predicted over the design space. Quality by Design (QbD) is a systematic approach to product development and process control that begins with predefined objectives, emphasizes product and process understanding, and sets up process control based on sound science and quality risk management. The Food and Drug Administration (FDA) and the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) have recently started promoting QbD in an attempt to curb rising development costs and regulatory barriers to innovation and creativity. QbD is partially based on the application of multivariate statistical methods and a statistical Design of Experiments strategy to the development of both analytical methods and pharmaceutical formulations. In this paper, we review the basics of QbD and their impact on the innovative, generic, and biosimilar pharmaceutical industry. In particular, we consider the challenge of mapping the control space in biotechnological processes and how advances in statistical methods can contribute to QbD.
Keywords: Quality by Design; Design of Experiments; Simulation experiments; Multivariate methods; Analytical methods; Specification limits; Biosimilars
Quantification of measurement uncertainty in the sequential determination of 210Pb and 210Po by liquid scintillation counting and alpha-particle spectrometry by Chang-Kyu Kim; Paul Martin; Aleš Fajgelj (pp. 691-702).
Methodologies for the quantification of measurement uncertainties associated with the determination of 210Pb- and 210Po-specific activities by liquid scintillation counting (LSC) and alpha-particle spectrometry are presented, and are demonstrated using the soil reference material IAEA-326. Major contributors to the combined uncertainty associated with the measurement result of 210Pb were the uncertainties of net count rates in the 210Pb energy region of the sample spectrum and in the 210Bi energy region of the blank spectrum. The predominant sources of uncertainty in the measurement of 210Po were the uncertainties of net count rates in the regions of interest of 209Po and 210Po. The relative standard uncertainty of 210Po exponentially increases with the time interval between the sampling date and the separation date of Po, and this effect is strongly dependent on the 210Po/210Pb activity ratio. When the specific activity of 210Pb is much higher than that of 210Po in the sample, the relative standard uncertainty of the 210Po determination increases significantly within a short time interval between the sampling date (or reference date) and the separation date of Po in samples.
Keywords: 210Pb; 210Po; Measurement uncertainty; Liquid scintillation counting; Alpha-particle spectrometry
The application of data from proficiency testing to laboratory accreditation according to ISO 17025 by Kaj Heydorn (pp. 703-709).
Current methods of testing laboratories for their proficiency in reporting correct measurement results are liable to substantial errors of the second kind. This means that laboratories with deflated uncertainties are accepted as proficient, even though their reported measurement results pave the way for erroneous conclusions. Only by using E n numbers based on an accepted reference value with the lowest possible uncertainty can the risk of recognising incorrect measurement results be kept at an acceptable level. Based on an actual set of proficiency test (PT)-data for the concentration of Pb in water, this paper compares PT results obtained by methods using E n numbers with methods based on z-scores.
Keywords: Laboratory accreditation; Proficiency testing; E n numbers; z-scores; Errors of the second kind; Type II error; Fiddle factor
Uncertainties when using dual-wavelength or single-wavelength spectrophotometry to monitor the course of hexavalent chromium reduction mediated by zero-valent iron by Mario Rivero-Huguet; William D. Marshall (pp. 711-716).
Chromium is ubiquitous; whereas in small amounts Cr(III) is vital in the diet of humans, Cr(VI) is highly toxic. The latter is commonly found in contaminated waters and brownfields worldwide. Zero-valent iron (Fe0) can detoxify Cr(VI) efficiently by mediating its reduction to Cr(III). In this study, a Cr(VI)-contaminated soil was treated with a surfactant solution (Tween® 20) and the resulting extract was reacted in acidic medium with Fe0. The disappearance of Cr(VI) with time was determined with the 1,5-diphenylcarbazide colorimetric method using single-wavelength spectrophotometry (SWS) and dual-wavelength spectrophotometry (DWS). The major sources of uncertainty in the measurements were identified and calculated in both cases. Over the entire course of the reaction, the uncertainty associated with the mass concentration of Cr(VI), γ(Cr), was decreased appreciably for the DWS method relative to the conventional (SWS) method of quantitation.
Keywords: Uncertainty measurement; Trace analysis; Hexavalent chromium; Dual-wavelength spectrophotometry; UV–vis spectrophotometry
Evaluation of the stability of ethanol in water certified reference material: measurement uncertainty under transport and storage conditions by Vanderléa de Souza; Janaína Marques Rodrigues; Raquel Duarte da C. Cunha Bandeira; Laura A. das Neves Valente; Marcus Vinícius Barreto Sousa; Viviane Fernandes da Silva; Rafael Agostinho Lemos da Silva (pp. 717-721).
This study simulated the transport and storage conditions of ethanol in water certified reference material (CRM) produced by the Chemical Metrology Division of Inmetro—DQUIM with the purpose of estimating the measurement uncertainty related to stability. The short-term stability study was performed on five different mass fractions (w) in terms of mg ethanol/g solution of the ethanol in water CRM. The nominal values are w = 0.5, 0.9, 1.1, 3.8 and 4.6 mg/g, at temperatures of 4 and 60 °C. On the other hand, the long-term stability study was developed on four different mass fractions (nominal values): w = 0.5, 0.9, 1.1 and 4.6 mg/g, at a temperature of 20 °C. This paper will show the data from the long-term stability study that took place over 52 weeks. The method used complies with ISO Guide 35, the BCR Guideline for Feasibility Studies and ISO Guide 34. According to the statistical parameters used in both studies, the stability of ethanol in water CRM was confirmed for all of the mass fractions studied.
Keywords: Certified reference material; Stability; Ethanol in water; Uncertainty
The distribution of interlaboratory comparison data by Kaj Heydorn (pp. 723-724).
The distribution of mutually consistent results from interlaboratory comparisons is expected to be leptokurtic, and readers are warned against accepting conclusions based on simulations assuming normality.
Keywords: Interlaboratory comparison; Heteroscedasticity; Leptokurtic distribution; Simulation
The distribution of interlaboratory comparison data: response to the contribution by K. Heydorn by David Lee Duewer (pp. 725-726).
The distribution of interlaboratory results can often be successfully modeled as a mixture of distributions: a “majority” population of results from laboratories of high and roughly equal competence and a (hopefully) minority “contaminant” population from laboratories of lesser competence. Approximating the majority population as a normal distribution and the contaminant as a uniform distribution can be and has been used to produce mixture populations that have realistically “heavy-tails” (i.e., leptokurtic).
ISO/IEC 17043: the new International Standard for proficiency testing by Daniel W. Tholen (pp. 727-730).
The revision of ISO/IEC Guide 43 is well underway by CASCO Working Group 28, with the author as Convener. The ballot on the committee draft was successfully completed in June 2008. The Working Group met in September to resolve the CD comments and to recommend that the document should advance as an ISO/IEC DIS. The document is in harmony with ISO/IEC 17025 (2005), ILAC G13 (2007), and the IUPAC Harmonized Protocol (2006) for proficiency testing. Major changes from Guide 43 include considerations for inspection bodies, requirements for metrological traceability of assigned values for calibration schemes, limitations on subcontracting, requirements for reporting the uncertainty of assigned values, and for including method information and technical commentary in scheme reports. Minor changes include requirements for equipment used in the manufacture and testing of proficiency test items, considerations for handling laboratories’ reported uncertainties, and the issuance of certificates of participation. These changes have not generated any substantial objections from the CASCO membership and liaisons.
Keywords: Proficiency testing; Interlaboratory comparisons; Inspection