01 September 2006
By:Yvan Vander Heyden
An experimental design can be considered as a series of experiments that, in general, are defined a priori and allow the influence of a predefined number of factors in a predefined number of experiments to be evaluated.
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01 May 2009
By:Bieke Dejaegher, Yvan Vander Heyden
Experimental designs are used in method development and robustness testing and have been discussed in an earlier article.1 An experimental design is an experimental set-up that allows the simultaneous examination of a predefined number of factors in a predefined number of experiments. Method development is often divided into a screening and an optimization step. During the first step, many factors, potentially affecting the method, are screened to determine the most important factors, which are then further optimized.1
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01 February 2009
By:Ricard Boqué, Yvan Vander Heyden
The concept of the limit of detection (LOD) has been, and still is, one of the most controversial in analytical chemistry. The multiple definitions and calculation methods proposed have contributed to this situation. Although in the last years, several international organizations, such as ISO or IUPAC, have tried to reach a consensus in their definitions and have issued guidelines for the estimation of this important parameter in chemical analysis, the subject is still a matter of scientific debate. In this article, we try to clarify the definition and provide guidelines to estimate LOD in chromatographic methods of analysis.
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01 December 2008
By:Alicia Maroto, Ricard Boqué, Yvan Vander Heyden
Estimating uncertainty has become one of the most important metrological concepts in analytical science over the last 15 years to such an extent that some authors consider a result useless or invalid unless it is accompanied with an uncertainty statement. This article describes how to estimate uncertainty in chromatographic analysis and how laboratories can calculate it using data from the method validation process.
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01 September 2008
By:Yvan Vander Heyden
Herbs and their extracts are currently being used for preventive and therapeutic goals. Consequently, the identification and quality control of these natural products is becoming increasingly important. Fingerprint chromatography is accepted as an appropriate identification and quality evaluation technique for medicinal herbs. This article reviews the development procedure of a fingerprint and different ways to handle the fingerprint data.
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01 May 2008
By:Ricard Boqué, Alicia Maroto, Yvan Vander Heyden
The assessment of accuracy, which involves the estimation of precision and the determination of trueness, refers to the process of evaluating whether the results provided by analytical methods are close to accepted reference values. The different references available in chromatographic analysis and useful guidelines to perform such a comparison are described.
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01 February 2008
By:B. Dejaegher, Y. Vander Heyden
Screening for important factors during method optimization or in robustness testing involves two-level screening designs, such as fractional factorial and Plackett–Burman designs, as described in Part 1. This second part on screening designs discusses the experimental protocol for executing these designs and the data analysis of their results.
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01 October 2007
By:Bieke Dejaegher, Yvan Vander Heyden
Screening designs are used to screen for important factors during method optimization or in robustness testing. Usually, two-level screening designs, such as fractional factorial and Plackett–Burman designs, are applied. This column discusses the properties of these designs.
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01 June 2007
By:Yvan Vander Hayden, Ricard Boqué, MaríaJosé Rodríguez Cuesta
Calibration refers to the process of determining the relation between the output (or response or signal) of a measuring instrument and the value of the input quantity or property. Depending on the univariate or multivariate character of the response (signal) used; either a univariate or a multivariate calibration is performed. The different calibration approaches are summarized in this article.
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