Identifier: TFG:1356
Authors: Jiménez Herraiz, Xavier
Abstract:
A study of validation statiscal parameters for an iron determination method in water samples of cooling towers and evaporative condensates, using UV/Vis spectrophotometry, routinely used in the Laboratory of Elecnor S.A. in Tarragona, is performed. The operation of cooling towers and the legislation, which is subject to the iron determination in these types of samples, is briefly described. Theoretical principle of spectrophotometry is explained and operation and general parts of a UV/Vis spectrophotometer are given. Analyte, matrix types and validation criteria are described, establishing acceptability ranges before the experimentation. Linearity, selectivity, repeatability, intermediate precision, trueness and robustness are studied; detection and quantification limits are calculated and the uncertainty is estimated. Tests are performed using surrogate samples with a certified standard, calculating the recoveries. In this way, we take into account a possible matrix effect on the analyte determination. Selectivity of the method is demonstrated by observing the UV/Vis absorption spectra of the reactant and indicator product, with maximum absorption wavelengths sufficiently separated. A possible chemical interferences are indicated, which we consider when working with surrogate samples calculating the recoveries. A good linearity in the selected work range, as well as, limits of detection and quantification more than enough for our purpose, are determined. Precision and trueness of the method satisfy the pre-established acceptance criteria, finding better precisions in the high concentration range. Method robustness is studied by introducing changes in the stipulated reaction time, not finding significant differences by performing an F-test and a t-test. The uncertainty estimation also satisfies the preset requirements, finding a higher uncertainty for the low concentration range.
Repositori URV