DETERMINAÇÃO DA INCERTEZA EXPANDIDA ASSOCIADA À ANÁLISE DE AÇÚCARES REDUTORES PELO MÉTODO DE LANEEYNON / DETERMINING THE UNCERTAINTY ASSOCIATED WITH THE EXPANDED ANALYSIS BY THE METHOD OF REDUCING SUGARS LANEEYNON

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

From the scientific viewpoint, the word uncertainty expresses doubt about an analytic result. The implementation of the concept of uncertainty of measurement is a crucial step that the Brazilian laboratories must take in the process for obtaining the certification of the ability to perform essays in accordance with the Brazilian technical norm ABNT NBR ISO/IEC 17025. Regardless the technical area of application, the determination of the uncertainty of measurement associated with the result of an analysis is extremely important, especially in the food industry. The expanded uncertainty is related with the degree of reliability of an analytical result, and by means of this information it is possible to evaluate if the result of an analysis is consistent, i.e., if the uncertainty associated to the measurement remains inside an acceptable range. When the percentage of uncertainty exceeds a threshold, it is necessary to find the process variables that more intensely contribute to increasing the uncertainty and, in the sequence, to take corrective actions in order to minimize the impact caused for those variables over the uncertainty of measurement. The aim of this study was to detect the uncertainty of measurement associated with the analysis of total reducing sugars (TRS) by the Lane-Eynon method. The equipments used were analytical and semi analytical balances, burettes with 10mL and 25mL, and the food matrix studied was wild honey. To perform the calculations of the standard uncertainty, u, information about the uncertainty of the laboratory materials used in the analysis obtained from the certificate of calibration. The combined uncertainty, uc, was obtained by deriving the influence factors and considering, if necessary, the effective degree of freedom, υeff, as stated in the Welch-Satterthwaite equation. The expanded uncertainty, U, was obtained by multiplying uc by the appropriate coverage factor, k = 2 (at level of confidence of 95,45%). The results showed that the expanded uncertainty obtained for the analysis of TRS was less than 2,0% when the analytical balance was used. The process variable having the greatest impact was the volume (close to 80,0%), followed by the title (close to 20,0%). The analysis of the expanded uncertainty obtained for the analysis of TRS when the semi analytical balance, and 10mL as well as 25mL burettes were used provided reliable results. However, care must be taken in such a combination of equipments, especially when using the 25mL burettes, since the percentage of uncertainty was great than 3,5%, too close to the limit established by the Codex Alimentarius, 4,0%. It was observed that, in this case, the variable having the greatest impact on the uncertainty was the title, with 79,82% (10mL burettes), and 87,10% (25mL burettes).

ASSUNTO(S)

açúcares redutores totais (art) incerteza expandida e confiabilidade. ciencia e tecnologia de alimentos total reducing sugars (trs) expanded uncertainty and reliability.

ACESSO AO ARTIGO

Documentos Relacionados