Unraveling measurement in chemical analysis: 1. The analytical or calibration curve

Bahia Filho, Oscar; Prada, Patricia Regina; Meneghesso, Carla; Lanças, Fernando M.

Palavras-chave: Measurement uncertainty, analytical or calibration curve, HPLC, LC-MS/MS, quality system management, ISO 17025, GLP guidelines.

Resumo:  In a typical quantitative chemical analysis, the mathematical model used for the quantification process is responsible for the transformation of a measured unit into the quantity of interest. Once dealing with a series of operations, the possibility of propagation of errors is a real concern; the trustworthiness of all these operations must be well established and be known. The present work, the first one of a series, aims to present and discuss the contribution of the stage of construction of the analytical or calibration curve in the process of the assay by estimating its uncertainty based upon the ISO 17025 and GLP guidelines. The application of these concepts culminated in the elaboration of an operational procedure that was applied to the determination of fluazuron in animal tissues using liquid chromatography coupled to mass spectrometer (LC-MS/MS).

Referências Bibliográficas

1. Bahia Filho O. A importância da metrologia química nos resultados das análises de resíduos. Scientia Chromatographica 2009; 1(4):49-54.

2. González FJE, Torres MEH, Frenich AC, Vidal JLM, Campana AMC. Internal quality-control and laboratory-management tool for enhancing the stability of results in pesticide multi-residue analytical methods. Trends in Analytical Chemistry 2004; 23.(5):361-369.

3. International Laboratory Accreditation Cooperation – ILAC. ILAC-P14:12/2010: ILAC policy for uncertainty in calibration. ILAC, 2010.

4. Associação Brasileira de Normas Técnicas – ABNT. NBR ISO/IEC 17025: Requisitos gerais para a competência de laboratórios de ensaio e calibração. Rio de Janeiro: ABNT, 2005.

5. Associação Brasileira de Normas Técnicas – ABNT. NBR ISO 9001:2008: Sistemas de gestão da qualidade – Requisitos. Rio de Janeiro: ABNT, 2009.

6. Instituto Nacional de Metrologia, Normalização e Qualidade Industrial – INMETRO. NIT-DICLA-035: Requisitos gerais para laboratórios segundo os princípios das boas práticas de laboratório (BPL). INMETRO, 2009. Revisão 01.

7. González AG, Herrador MA. A pratical guide to analytical method validation, including measurement uncertainty and accuracy profiles. Trends in Analytical Chemistry 2007; 26(3):227-238.

8. Instituto Nacional de Metrologia, Normalização e Qualidade Industrial – INMETRO. DOQ-CGCRE-008: Orientação sobre validação de métodos analíticos. INMETRO, 2011. Revisão 04.

9. Thompson M, Wood R. Harmonized guidelines for internal quality control in analytical chemistry laboratories (Technical Report). Pure and Applied Chemistry. 1995; 67(4):649-666. http://dx.doi. org/10.1351/pac199567040649

10. Meyer VR. Measurement uncertainty. Journal of Chromatography A 2007; 1158(1-2):15-24. http:// dx.doi.org/10.1016/j.chroma.2007.02.082

11. Ratola N, Santos L, Herbert P, Alves A. Uncertainty associated to the analysis of organochloride pesticides in water by solid-phase microextraction/ gás chromatography-electron capture detection – Evaluation using two different approaches. Analytica Chimica Acta 2006; 573-574:202-208. http://dx.doi. org/10.1016/j.aca.2006.03.065