New advances in method validation and measurement uncertainty aimed at improving the quality of chemical data (original) (raw)
Related papers
TrAC Trends in Analytical Chemistry, 2004
Credibility of analytical data has never caught the public's eye more than today. The key principle for quality and reliability of results is comparability between laboratories and on a wider, international basis. In order to be comparable, analytical results must be reported with a statement of measurement uncertainty (MU) and they must be traceable to common primary references. This work focuses on traceability and uncertainty of results. We discuss different approaches to establishing traceability and evaluating MU. We place both concepts in the broader context of analytical method validation and quality assurance. We give up-to-date information in the framework of new, more exacting European and international standards, such as those from Eurachem/CITAC, IUPAC and ISO.
Uncertainty profiles for the validation of analytical methods
Talanta, 2011
This article aims to expose a new global strategy for the validation of analytical methods and the estimation of measurement uncertainty. Our purpose is to allow to researchers in the field of analytical chemistry get access to a powerful tool for the evaluation of quantitative analytical procedures. Indeed, the proposed strategy facilitates analytical validation by providing a decision tool based on the uncertainty profile and the -content tolerance interval. Equally important, this approach allows a good estimate of measurement uncertainty by using data validation and without recourse to other additional experiments. In the example below, we confirmed the applicability of this new strategy for the validation of a chromatographic bioanalytical method and the good estimate of the measurement uncertainty without referring to any extra effort and additional experiments. A comparative study with the SFSTP approach [1] showed that both strategies have selected the same calibration functions. The holistic character of the measurement uncertainty compared to the total error was influenced by our choice of profile uncertainty. Nevertheless, we think that the adoption of the uncertainty in the validation stage controls the risk of using the analytical method in routine phase.
Validation of analytical methods and laboratory procedures for chemical measurements
Arhiv za higijenu rada i toksikologiju, 1998
Method validation is a key element in the establishment of reference methods and in the assessment of a laboratory's competence in producing reliable analytical data. Hence, the scope of the term "method validation" is wide, especially if one bears in mind the role of Quality Assurance/Quality Control (QA/QC). The paper puts validation in the context of the process generating chemical information, introduces basic performance parameters included in the validation processes, and evaluates current approaches to the problem. Two cases are presented in more detail: the development of European standard for chlorophenols and its validation by a full scale collaborative trial and the intralaboratory validation of a method for ethylenethiourea by using alternative analytical techniques.
TrAC Trends in Analytical Chemistry, 2004
It is internationally recognized that validation is necessary in analytical laboratories. The use of validated methods is important for an analytical laboratory to show its qualification and competency. In this update on analytical quality, we place validation of analytical methodologies in the broader context of quality assurance (QA). We discuss different approaches to validation, giving attention to the different characteristics of method performance. We deal with the concepts of single-laboratory or in-house validation, inter-laboratory or collaborative study, standardization, internal quality control (IQC), proficiency testing (PT), accreditation and, finally, analytical QA (AQA).
Quality Assurance and Quality control in chemical and physical Analysis. 2009, 383 - 388
Analytical measurements are important part for many human activities and in such cases they used in order to take important decision in the problem of economy, technology of production, environment, legislation etc. Evaluation of quality in different productivities and materials, process control of produce, consumer assurance, environment protection and healthy safeguard of people are some of the important activity that based in chemical and physical analysis. Basic problem for all quality system is establishment of reliability in the results that give laboratory. But, reliability toward the laboratory must exist only if it based in reliability of measurement which prove these quality. Today the important problems of analytical measurement are establishment of quality system, quality assurance and quality control of measurements in analytical laboratory. In the end of this purpose is that laboratory must provide to consumers some analytical data with known quality (acceptable).
Some practical examples of method validation in the analytical laboratory
TrAC Trends in Analytical Chemistry, 1999
Method validation is a key element in both the elaboration of reference methods and the assessment of a laboratory's competence in producing reliable analytical data. Hence, the scope of the term method validation is wide, especially if one bears in mind that there is or at least should be a close relation between validation, calibration and quality control QA /QC. Moreover, validation should include more than the instrumental step only since the whole cycle from sampling to the ¢nal analytical result is important in the assessment of the validity of an analytical result. In this article validation is put in the context of the process of producing chemical information. Two cases are presented in more detail: the development of a European standard for chlorophenols and its validation by a full scale collaborative trial, and the intralaboratory validation of a method for ethylenethiourea using alternative analytical techniques.
Evaluating uncertainty in analytical measurements: the pursuit of correctness
Springer eBooks, 1998
Simple in principle, the evaluation of uncertainty, especially in chemical analysis, is not a routine task and needs great care to be correct. This can be seen, particularly, from an examination of the EURACHEM Guide, Quantifying Uncertainty in Analytical Measurement (1995), which is the most important document on the subject. The examination reveals, in the author's opinion, a shortage of correctness in some principal details of the uncertainty estimation process as presented in worked examples in the Guide, and the author has therefore formulated some "in pursuit of correctness" rules for estimating uncertainty. The rules and respective comments are concerned with the following items: (1) choosing an appropriate distribution function in type B evaluation of uncertainty, (2) the necessity for consideration of separate contributions to the combined uncertainty, and (3) taking account of actual influence factors in the uncertainty estimation process. Furthermore, the problem of estimation of conditional versus overall uncertainty is touched upon in connection with comparative trials where only internal consistency of results is required.
Quality and Reliability Engineering International, 2008
In industry and in laboratories, it is crucial to continuously control the validity of the analytical methods used to follow the products' quality characteristics. Validity must be assessed at two levels. The "pre-study" validation aims at demonstrating before use that the method will be able to achieve its objectives. The "in-study" validation is intended to verify, by inserting QC samples in routine runs, that the method remains valid over time. At these two levels, the analytical method will be claimed valid if it is possible to prove that a sufficient proportion of analytical results is expected to lie within given acceptance limits [−λ,λ] around the nominal value. This paper presents and compares four approaches to checking the validity of a measurement method at the pre-study level. They can be classified into two categories. In the first, a lower confidence bound for the estimated probability π of a result lying within the acceptance limits is computed and compared to a given acceptance level. Maximum likelihood and delta methods are used to estimate the quality level π and the corresponding estimator variance. Two approaches are then proposed to derive the confidence bound: the asymptotic maximum-likelihood approach and a method proposed by Mee . The second category of approaches checks whether a tolerance interval for hypothetical future measurements lies within the predefined acceptance limits [−λ,λ]. β-expectation and β-content tolerance intervals are investigated and compared in this context. These four approaches are illustrated on a bioanalytical HPLC-UV analytical process and compared through simulations.
Drug Testing and Analysis, 2010
Estimation of measurement uncertainty (MU) for quantitative results is a requirement of ISO/IEC17025. This concept is well established for chromatographic methods in doping control and forensic analysis. For non-chromatographic methods, however, very few practical methodologies have been published. In this paper, the applicability of a top-down model, established for estimating uncertainty in chromatography, was evaluated for two other methodologies with different sets of raw data as a starting point. The first case study involves the estimation of MU for the determination of haematological parameters. In this case, a large data set of quality control material and proficiency testing results was available to establish MU. The second case study involves the estimation of MU for the recently approved method for the determination of human growth hormone misuse. In this case the amount of data available to establish MU was limited to results from method validation and a basic set of analysis data. In both cases a methodology based upon long-term bias, long-term imprecision and-eventually-a correction for standard impurity is proposed. The proposed methodology can be regarded as a dynamic procedure, which allows re-evaluation of MU on a regular basis. Finally, a concept for the verification and evaluation of MU estimations using proficiency testing results is proposed.
Measurement uncertainty in analytical methods in which trueness is assessed from recovery assays
Analytica Chimica Acta, 2001
We propose a new procedure for estimating the uncertainty in quantitative routine analysis. This procedure uses the information generated when the trueness of the analytical method is assessed from recovery assays. In this paper, we assess trueness by estimating proportional bias (in terms of recovery) and constant bias separately. The advantage of the procedure is that little extra work needs to be done to estimate the measurement uncertainty associated to routine samples. This uncertainty is considered to be correct whenever the samples used in the recovery assays are representative of the future routine samples (in terms of matrix and analyte concentration). Moreover, these samples should be analysed by varying all the factors that can affect the analytical method. If they are analysed in this fashion, the precision estimates generated in the recovery assays take into account the variability of the routine samples and also all the sources of variability of the analytical method. Other terms related to the sample heterogeneity, sample pretreatments or factors not representatively varied in the recovery assays should only be subsequently included when necessary. The ideas presented are applied to calculate the uncertainty of results obtained when analysing sulphides in wine by HS-SPME-GC.