Validação do método modificado de Monier Williams para quantificação de Sulfito por titulometria na matriz de Caranguejo: método usado no Laboratório de Inspecção de pescado de Quelimane

Abstract

The application of any new method in laboratory analysis must undergo a validation to better be sure of the results. Unfortunately in the Fish Inspection Laboratory of Quelimane uses the nonstandard method and not validated for the qualification of sulphate in crab matrix, thus not guaranteeing the quality of the results of its analyzes, hence the present work aims to Validate the Modified Method of Monier Williams Used for Qualification of Sulphite in the Crab Matrix. For the purpose it was directly evaluated the method demonstrated the accuracy and indirectly the method demonstrating specificity/sensitivity; linearity; sensitivity; limits detention and quantification; precision and robustness. The Accuracy of the method was estimated from the recovery of the sulfite in fortified samples analyzed by analysts other than 25, 75 e 150ppm, where at all points recovered within the acceptable limit of 70 to 110%; Specificities/Selectivity was estimated from the analyte in the stress sample (HCl, NaOH, H2O2, fluorescence and temperature), where it showed results of recovery of the analyte within the acceptable limit in sample in all stress media conserved in the freezer and stress with HCl in the glacier as well as the freezer; the Linearity of the method was determined by the determination of sulphite in the fortified samples in six points (25,50, 75, 100, 125, 150ppm) where showed R=0.9974 there was great correlation; the Sensitivity of the method corresponds to the coefficient angle of straight, was determined together with the linearity, where, b=0.8825 corresponding to the angle of 41.46o.indicating optimal slope of the line; the Limits of Detention and Quantification of the method were determined from the concentration regression of 25ppm up to 17.5ppm, where the detention limit was 15ppm and the limit of quantification was 22.76ppm; the Precision of the method was determined together with the accuracy of the method, in which the repeatability was verified by presenting results followed by the same analysts smaller than the repeatability and reprodutybility because it did not present variation in its means and variance in the results of the two analysts; robustness was determined by the acceptable recovery of sulphite even by varying the sulfite flow time, demonstrating that the increased sulphite flow time did not influence the result of the analysis. The Modified Monier Williams Method used in de Quelimane Fish Inspection Laboratory is valid for quantification of sulphite by titration in the crab matrix.