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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement
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Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0949-1775 - ISSN (Online) 1432-0517
Published by Springer-Verlag

[2355 journals]

Congress, conferences, workshops and courses
- Pages: 233 - 233
  PubDate: 2017-08-01
  DOI: 10.1007/s00769-017-1278-4
  Issue No: Vol. 22, No. 4 (2017)
Congress, conferences, workshops and courses
- Pages: 169 - 170
  PubDate: 2017-06-01
  DOI: 10.1007/s00769-017-1267-7
  Issue No: Vol. 22, No. 3 (2017)
Development of primary standard gas mixtures containing 10 µmol/mol
oxygen in nitrogen with verification by a two-oven GC-TCD system for
effective separation of oxygen from argon in presence of plenty of
nitrogen
- Authors: Takuya Shimosaka
  Abstract: Primary standard gas mixtures (PSMs) containing 10 µmol/mol oxygen in nitrogen were prepared in aluminum alloy cylinders from pure nitrogen and oxygen gases according to ISO 6142-1. We developed a system consisting of a gas chromatograph with a thermal conductivity detector (GC-TCD) and two ovens to verify precisely the amount-of-substance fraction of oxygen in the PSMs at a level of 10 µmol/mol. As pure nitrogen gas usually contains argon as an impurity, it is necessary to separate the oxygen peak from the argon peak in order to verify the amount-of-substance fraction of oxygen in the PSMs. Although the use of packed columns is essential in order to achieve high precision using a GC-TCD system, it is notoriously difficult to separate oxygen and argon by this method. To overcome this problem, we used two gas chromatograph ovens: The first oven separates oxygen and argon from the nitrogen, whereas the second oven—held at −15 °C or below—separates oxygen and argon. The two-oven GC-TCD system was able to achieve good resolution between the oxygen and argon peaks. The relative uncertainty in the determination of the oxygen fraction obtained using this system was 0.35 %. In order to avoid adsorption of oxygen onto the inner surface of the aluminum cylinder, we pretreated each cylinder by filling it with a standard gas mixture of oxygen in nitrogen at an oxygen partial pressure similar to that of the PSMs. The cylinders were then evacuated and used for the preparation of the target PSMs. From long-term monitoring using the GC-TCD system, we found the PSMs containing 10 µmol/mol oxygen in nitrogen to be stable for at least 30 months. The expanded combined uncertainties for the PSMs (k = 2) were found to be 0.026 µmol/mol to 0.036 µmol/mol, according to ISO 6142-1.
  PubDate: 2017-07-21
  DOI: 10.1007/s00769-017-1279-3
Uncertainty estimation of the determination of chemical sum parameters in
water
- Authors: Tony Venelinov
  Abstract: Sum parameters (otherwise known as composite parameters) describe similar chemical, physicochemical or biological characteristics of different substances, substance groups or mixtures of substances. These might contain the same chemical element. Such parameters are total organic carbon or total bound nitrogen. Chemical oxygen demand is a shared chemical characteristic—the oxidizability of constituents by dichromate. The focus of the paper is on the uncertainty estimation of the determination of chemical sum parameters in water samples from method validation derived data—total organic carbon, chemical oxygen demand, biochemical oxygen demand, total bound nitrogen and total suspended solids. The results for the measurement uncertainty estimations according to ISO 21748 and ISO 11352, as only applicable to the field of water analysis, are presented and compared. Based on the results obtained and the experimental design, the use of ISO 11352 for the measurement uncertainty estimation is recommended. This international standard employs fewer determinations (a minimum number of eight measurements are required, compared to fifteen), fewer working days (one compared to five) and easier measurement uncertainty components’ calculations and even gives opportunity for routine laboratories to use standard solutions over the more expensive certified reference materials for the measurement uncertainty estimation during the method validation in water analysis.
  PubDate: 2017-07-12
  DOI: 10.1007/s00769-017-1276-6
G. Férard, R. Dybkaer and X. Fuentes-Arderiu: Compendium of terminology
and nomenclature of properties in clinical laboratory sciences,
recommendations 2016 (Silver Book, 2nd ed.)
- Authors: David B. Hibbert
  PubDate: 2017-07-12
  DOI: 10.1007/s00769-017-1277-5
Uncertainty evaluation for the determination of the dissolved fraction of
sulpiride content in tablets
- Authors: Biying Du
  Abstract: The aim of this work was to establish a mathematical model to identify the main source of measurement uncertainty, quantify each uncertainty component, and calculate the combined and expanded uncertainties for determination of the fraction of sulpiride dissolved from tablets by UV spectrophotometry. The uncertainties on the absorbance (sample and standard), volumetric flasks and volumetric pipettes have important influence on the overall uncertainty. The average sulpiride fraction released from six tablets was 75.5 %, with an expanded uncertainty of 3.7 % (k = 2). Uncertainty is a relevant tool in assessment of compliance or non-compliance of in-process and final pharmaceutical products. Evaluation of the uncertainty of the dissolution measurement contributes to scientific explanation and interpretation of testing data, and ensures the results to be more accurate, impartial and convincing when testing a sample against specification or legislation.
  PubDate: 2017-06-29
  DOI: 10.1007/s00769-017-1273-9
A statistical procedure for the assessment of bias in analytical methods
using conditional probabilities
- Authors: Robert B. Frenkel; Ian Farrance
  Abstract: A new approach is described for the simultaneous treatment of bias and imprecision in clinical chemistry. The approach makes use of the general law of conditional probabilities. The result is a density distribution of the measurand that incorporates both imprecision and bias and avoids the contentious linear combination of these quantities as a ‘total error’. This leads naturally to a figure-of-merit in proficiency testing or method comparison that has intuitive visual appeal. We also discuss an established figure-of-merit in proficiency testing, namely the E n number.
  PubDate: 2017-06-29
  DOI: 10.1007/s00769-017-1274-8
Full method validation in clinical chemistry
- Authors: Elvar Theodorsson; Bertil Magnusson
  Abstract: Clinical chemistry is subject to the same principles and standards used in all branches of metrology in chemistry for validation of measurement methods. The use of measuring systems in clinical chemistry is, however, of exceptionally high volume, diverse and involves many laboratories and systems. Samples for measuring the same measurand from a certain patient are likely to encounter several measuring systems over time in the process of diagnosis and treatment of his/her diseases. Several challenges regarding method validation across several laboratories are therefore evident, but rarely addressed in current standards and accreditation practices. The purpose of this is paper to address some of these challenges, making a case that appropriate conventional method validation performed by the manufacturers fulfils only a part of the investigation needed to show that they are fit for purpose in different healthcare circumstances. Method validation across several laboratories using verified commercially available measuring systems can only be performed by the laboratories—users themselves in their own circumstances, and need to be emphasised more by the laboratories themselves and accreditation authorities alike.
  PubDate: 2017-06-29
  DOI: 10.1007/s00769-017-1275-7
Evaluation and optimisation of methylene blue removal measurement
uncertainty in photodegradation studies
- Authors: Nuno F. Rosa; O. C. Monteiro; M. Filomena Camões; Ricardo. J. N. Bettencourt da Silva
  Abstract: The photodegradation of carcinogenic and teratogenic organic contaminants, such as active substances of medicines or preservatives of personal care products, not removed from wastewaters by conventional treatments, is a promising solution to reduce the impact of such emissions. Nevertheless, new catalysts need to be developed to make this technology feasible. Catalysts performance can be assessed from photodegradation tests using degradation markers such as methylene blue. The difference between the photodegradation kinetic constants of two catalytic alternatives is meaningful if its absolute value is larger than the expanded uncertainty of the difference, which results from the combination of relevant measurement uncertainty components, namely pollutant concentration before and after depletion and irradiation time. This work presents algorithms for estimating differences of kinetic constants of methylene blue removal, with uncertainty, implemented in a user-friendly MS Excel spreadsheet. The developed measurement models allow the optimisation and reliable comparison of kinetic constants. This tool is particularly useful to distinguish small efficiency differences of catalysts with equivalent production and use costs. If a portion of the methylene blue solution subjected to irradiation is used to calibrate the spectrometer between 0.26 mg L−1 and 1.3 mg L−1 in a wavelength interval between 550 nm and 700 nm, if the solution irradiation time is larger than 11 min and the irradiated solution is quantified after dilution with negligible uncertainty, it is possible to distinguish the difference of kinetic constants between 0.11 ms−1 and 0.56 ms−1.
  PubDate: 2017-06-06
  DOI: 10.1007/s00769-017-1272-x
How to encompass an uncorrected bias into the expanded uncertainty with a
fixed coverage probability: calculation procedures
- Authors: Václav Synek
  Abstract: The practice in analytical and medical laboratories often necessitates evaluating the uncertainty of measurement in such a way that incorporates the bias in the expanded uncertainty of measurement instead of correcting for it. This paper presents a complete procedure for calculating the coverage interval that is delimited with one of these approaches. The obtained interval is symmetrical with respect to the uncorrected measured value (x) and has a determined coverage probability (p) under a given bias (b) and combined standard uncertainty (u c ); the approach is denoted by U e (p). A possibility of this approach was suggested by Synek (Talanta 65:829–837, 7). The stated procedure enables to choose frequently used coverage probabilities (mainly 95 % and 99 %). The calculation of the U e (p) expanded uncertainty requires quantifying a factor that multiplies u c . Its values depend on p, on b/u c and also on the effective number of degrees of freedom (ν) of u c , especially at ν of a small size; these values can be found in the attached tables. Since this accurate calculation can be qualified as too complex, a simplification is recommended by using two approximations that are applicable provided ν ≥ 6.
  PubDate: 2017-06-03
  DOI: 10.1007/s00769-017-1268-6
Development of milk powder reference material and its use for evaluation
of laboratory performance on analysis of mandatory nutrients for nutrition
labelling in Thailand
- Authors: Kunchit Judprasong; Prapasri Puwastien; Jutharat Supanuwat; Sitima Jittinandana; Naruemol Pinprapai
  Abstract: This study investigated the laboratory performance on the analyses of mandatory nutrients for nutrition labelling in Thailand and aimed to upgrade the proficiency test (PT) material into a reference material (RM). This milk powder with sufficient homogeneity and multiple nutrient compositions provided an acceptable PT material. Twenty ISO 17025 accredited laboratories participated in this study, and analytical performance was investigated using ISO 17043 and ISO 13528 standards. Satisfactory performance ( z ≤ 2, for both within- and between-laboratory variations) was found among participating laboratories on the analyses of total fat, saturated fat, cholesterol, protein, sugar, sodium, vitamin B1, vitamin B2, calcium, iron, moisture, and ash. The values of these nutrients (mean and standard deviation) were applied to upgrade the PT material to be used as a reference material. For a trial, moisture, vitamin B1, and vitamin B2 were selected as three representative nutrients to develop reference values as mean and uncertainty following ISO Guides 34 and 35 for RM production. The mean of moisture, vitamin B1, and vitamin B2 values of 2.34 g/(100 g), 0.64 mg/(100 g), and 0.78 mg/(100 g) were obtained with the relative expanded uncertainty of 12.2 %, 12.7 %, and 9.7 %, respectively. The developed RM can be used as quality control sample or as PT material with reference nutrient values among the laboratories in Thailand.
  PubDate: 2017-05-26
  DOI: 10.1007/s00769-017-1269-5
Evolution of quality on pharmaceutical design: regulatory requirement?
- Authors: AnaCerúlia Moraes doCarmo; Marcilio S. S. Cunha-Filho; Guilherme Martins Gelfuso; Tais Gratieri
  Abstract: Quality by design (QbD) concept was first outlined by quality pioneer Joseph M. Juran, who believed quality could be designed into a product, preventing, therefore, most quality problems, normally related to the way quality was planned. This concept, as others related to quality conception and management, has already been applied by other industries, as automotive, and later introduced to pharmaceutical industry through US Food and Drug Administration and The International Council on Harmonization of Technical Requirements for Medicinal Products for Human Use guidelines. Brazil mostly applies statistical quality control and still does not have specific regulations regarding QbD, neither other countries in Latin America. Thus, the current stage of pharmaceutical quality regulation in Latin America must be understood to implement better strategies that can positively affect the development of drug products to reach advanced levels of quality. This article reviews aspects related to quality of pharmaceutics and assesses data to analyze whether Brazilian pharmaceutical industry can adapt to this scenario as a pilot for other South American countries.
  PubDate: 2017-05-26
  DOI: 10.1007/s00769-017-1270-z
Combined uncertainty factor for sampling and analysis
- Authors: Michael H. Ramsey; Stephen L. R. Ellison
  Abstract: Measurement uncertainty that arises from primary sampling can be expressed as an uncertainty factor, which recognises its sometimes approximately log-normal probability distribution. By contrast, uncertainty arising from chemical analysis is usually expressed as relative uncertainty, based upon the assumptions of its approximately normal distribution. A new method is proposed that enables uncertainty from these two sources, expressed in these different ways, to be combined to produce an estimate of the total combined uncertainty of the measurement values that result when the measurement process is considered as a whole.
  PubDate: 2017-05-26
  DOI: 10.1007/s00769-017-1271-y
Identifying the critical cut-points of a quality control process for
serological assays: results from parametric and semiparametric regression
models
- Authors: Handan Wand; Wayne Dimech; Robert Freame; Kathy Smeh
  Abstract: Quality control programs rely on continuous monitoring which may generate large volume of complex data. Assessing the precision of a biological assay using quality control processes is essential to evaluate the daily variations in a testing system. Variation can be introduced by reagents, instruments and operators, as well as biological changes in the populations screened. We have proposed a statistical analysis framework which combines novel statistical analysis and visualization techniques to determine the functional relationship between the quality control and blood donor’s negative results. Flexible semiparametric regression techniques were used to determine the functional relationships between blood donor’s hepatitis B surface antigen and anti-HIV test results and the reactivity of quality control samples over a period of 9 months. We demonstrated that the use of semiparametric regression models in conjunction with the probabilistic approaches may bring comprehensive insight into understanding the significant temporal features of the data and its impact on patient’s test results. In the absence of clinically relevant cut-point(s), data-driven methodologies, such as the one described in this study may potentially have significant benefits and widespread applications.
  PubDate: 2017-05-19
  DOI: 10.1007/s00769-017-1265-9
Establishment of an analytical method for accurate purity evaluations of
acylcarnitines by using quantitative 1 H NMR spectroscopy
- Authors: Naoki Saito; Takeshi Saito; Taichi Yamazaki; Yoshinori Fujimine; Toshihide Ihara
  Abstract: Recently, it has become possible to examine metabolism abnormalities by detecting increases in specific acylcarnitines in blood tests of newborn babies using tandem mass spectrometer. However, acylcarnitine standard solutions with metrological traceability to the International System of Units (SI) for accurate calibration of tandem mass spectrometer are not yet available worldwide. In this study, we examined a quantitative 1H NMR procedure for obtaining accurate and SI-traceable purity evaluations of acylcarnitines having different numbers of carbon atoms as each raw material for their standard solutions. In particular, the solvent composition and measurement temperature were optimized to reduce the influence of water signal overlapping on analyte signals. It was found that, when the signal of that 1H which directly bound to the asymmetric carbon of the acylcarnitine is the target signal, it was possible to reduce overlapping of the water signal on the target signal by using deuterium oxide as a solvent. On the other hand, in the case of an acylcarnitine that was poorly soluble in deuterium oxide, it was possible to reduce overlapping of the water signal on the target signal by adding an appropriate amount of deuterium oxide to methanol-d 4 in which the acylcarnitine had high solubility. At this time, the optimum mixing volume ratio of methanol-d 4/deuterium would be 80:20. The overlapping of the water signal could be also reduced when the measurement temperature was 15 °C to 40 °C. When the measurement temperature was an around room temperature (in this study, 25 °C), fine shimming could be performed easily. Therefore, the optimum temperature would be 25 °C, because fine shimming was essential to quantify any signal area accurately. Finally, this study confirmed that accurate values with SI traceability could be obtained at about 1 % or less expanded uncertainty for five kinds of acylcarnitines.
  PubDate: 2017-04-29
  DOI: 10.1007/s00769-017-1263-y
European analytical column number 45
- Authors: Wolfgang Buchberger; Slavica Razic
  PubDate: 2017-04-28
  DOI: 10.1007/s00769-017-1266-8
Note on the correction of negative measured values if the measurand is
positive or 0 with known probability
- Authors: Peter-Th. Wilrich
  Abstract: Often the amount of a substance or the activity of radionuclides in a sample is measured indirectly as the difference between signal and noise, i.e. the difference between the measured value obtained at the sample and that obtained at a sample not containing the substance or the radionuclides (blank sample). The difference can be negative, especially if the concentration or the activity is low. Since a negative measurement result for a nonnegative measurand does not make sense, measured values must be corrected to nonnegative measurement results. We deal with the situation in which it is known that the measurand is 0 with a probability \(p_0\) that is a priori known, and that the standard deviation \(\sigma\) of the measurement is known. For this case Korun, Vodenik and Zorko extend an earlier paper by Korun and Zorko and derive the mean of the posterior distribution as a Bayesian estimator of the measurand. We offer an estimator that is based on the posterior probability \(\hat{p}_0\) of the measurand being 0. If \(\hat{p}_0 > 1 - \hat{p}_0\) it is 0 and otherwise the mode of the posterior distribution. This estimate is easier to calculate and less biased than that of Korun et al.
  PubDate: 2017-04-26
  DOI: 10.1007/s00769-017-1264-x
Mass emissions and carbon trading: a critical review of available
reference methods for industrial stack flow measurement
- Authors: C. Dimopoulos; R. A. Robinson; M. D. Coleman
  Abstract: Flow measurements in industrial ducts and stacks are combined with pollutant or greenhouse gas concentrations to deduce mass emissions. These are then used to populate pollutant emission inventories and are traded under emissions trading schemes. Reference methods for flow are described in ISO 10780 and more recently in EN ISO 16911-1. This paper discusses the key differences between the two standards. We consider sources of error in flow measurement and discuss how each standard addresses them. We find that EN ISO 16911-1 introduces a series of improvements that when combined provide critical uncertainty gains that support compliance with the EU’s Emissions Trading System (EU ETS). All these areas are either not addressed or only partially dealt with in ISO 10780. More specifically, EN ISO 16911-1, (a) specifies a wider range of reference techniques enabling the optimal one to be used for different flue gas environments. (b) Provides a method to correct for cyclonic flow effects. (c) Addresses measurement assembly misalignment and specifies tolerance values for it and (d) provides wall effect correction factors. Most importantly, it has been validated through laboratory and field work. However, the quality control specified in EN ISO 16911-1 is more suitable for measurements to support EU ETS requirements and at times can be too onerous for pollutant mass emission reporting that will usually have less stringent uncertainty requirements.
  PubDate: 2017-03-24
  DOI: 10.1007/s00769-017-1261-0
Organisation of proficiency schemes by testing and calibration
laboratories
- Authors: Rodrigo Leão Mianes; Carla Schwengber ten Caten
  Abstract: Each year, an increasing demand for proficiency testing is seen in the world. Participating in this type of activity has been adopted by testing and calibration laboratories, accredited under the ISO/IEC 17025 standard (General requirements for the competence of testing and calibration laboratories), as a means to meet normative and regulatory requirements. Nevertheless, the availability of proficiency testing schemes organised by providers accredited under the ISO/IEC 17043 standard (Conformity assessment—General requirements for proficiency testing) has been insufficient, which poses challenges to laboratories. Considering the similarities between requirements present in both standards, which would allow for their coexistence in a management system, this paper presents an analysis of potential conflicts of interest within an organisation operating simultaneously as proficiency testing provider and testing and calibration laboratory. Aspects of confidentiality, impartiality and undue internal pressures are discussed, and a procedure is proposed to mitigate such conflicts through a web application that codifies the relationship between laboratories and results with no human interaction. In order to minimise possible subjective aspects, the study was validated by a group of metrology specialists. It was concluded that the proposed simultaneous operation is possible and can effectively contribute to reduce shortage in the availability of such a service.
  PubDate: 2017-03-17
  DOI: 10.1007/s00769-017-1260-1
PAH analysis in biomass combustion wastes: an approach to evaluate bias
and precision of analytical results using routine samples
- Authors: Susana García-Alonso; Rosa María Pérez-Pastor; David Sanz-Rivera; Enrique Rojas-García; Jesús Rodríguez-Maroto
  Abstract: The aim of this work was to optimize and evaluate an analytical procedure to determine selected polycyclic aromatic hydrocarbons (PAHs) using real samples. Samples of ash were collected during biomass combustion tests under different operating conditions during one week. PAHs were quantified using liquid chromatography with fluorescence detection. Samples were extracted by a simple sonication/agitation method using small amounts of solvent and samples. This paper includes how the performance (bias and precision) of the proposed method was estimated from the analyses of samples. In order to obtain reliable data, we estimated the possible presence of two types of analytical bias: bias proportional bias to the level of analyte, expressed as recovery, and constant bias, comparing results from analyses of different ash masses. Apart from bias studies, the analytical variability was also evaluated as intermediate precision from the overall analyses of different routine samples, with different mass fraction levels and test dates. Intermediate precision values were reduced among 5 % to 10 % when measures on the optimized sample sizes and similar mass fraction levels were taken. The use of samples is rarely applied to assess trueness of analytical methods. Therefore, the presented findings can be considered as an interesting contribution to the analytical chemistry research field.
  PubDate: 2017-03-14
  DOI: 10.1007/s00769-017-1257-9