Accuracy of analytical standard solutions and the uncertainty in their nominal concentrations

Thursday, June 15, 2017

Authors: Árpád Ambrus, Kamirán Áron Hamow, Gabriella Kötelesné Suszter, Anikó Németh, Etelka Solymosné Majzik

 

1.     Summary


In the last step of the analysis, the accuracy of analytical standard solutions has a de­cisive influence on the measurement results of pesticide residues, as well as all other chemical contaminants, and, in the case of actual concentrations differing from no­minal ones, can result in a systematic error during the determination of sample com­ponents. Therefore, most of the laboratories who feel responsible for their results pay special attention to the preparation and storage of standard solutions, and to reple­nishing solvent losses due to possible evaporation, based on the mass measurements of vessels storing standard solutions before and after use. However, in our experience, much less attention than necessary is paid in practical work to monitoring the possible decomposition of individual active ingredients, and not appropriate statistical methods are used for the evaluation of the monitoring results. In our article, we present the stan­dard preparation methods of two laboratories employing “good analytical practices”, analyze the uncertainties of the different steps, and make a recommendation for the preparation of the most accurate standard solutions.

 

2. Introduction

For authority and national reference laboratories of European Union member states it is mandatory to participate in the relevant proficiency tests. A ring test (EU-RT-FV17) was organized by the European Union Reference Laboratory for Pesticide Residues in Fruit & Vegetables to reveal the reasons for results that proved to be inadequate, based on the criteria used for the evaluation of the performance of participating labo­ratories.

 

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