Unraveling the measurement in chemical analysis: 2. Traceability of Measurement

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

Palavras-chave: Traceability, measurement uncertainty, standard operating procedure, statistical process control, method validation.

Resumo: Since the adoption of the guidelines of the ABNT NBR ISO/IEC 17025, the term traceability of results has been used by accreditation bodies as part of the requirements inherent demonstrable during an auditing. For metrology physical the demonstration of traceability can be easily made by the nature of the measure, already for chemical metrology, this demonstration is not so simple, because the chemical tests, as a rule, are indirect measures, ie, results the concentration of the component in the sample is obtained by measuring other quantities / units from the different units expressed in reports. In addition the transformation of the measuring unit, another characteristic of chemical testing is the use of a set of equipment used in various steps in a single assay. Thus, the traceability of a test chemical can be represented by the standard operating procedure used and the intrinsic uncertainty of the process, not just for the traceability in its orthodox concept to the SI. This work, second of the series, aims to discuss the contribution of uncertainty concerning the traceability of equipment used in comparison to the uncertainty concerning the traceability of driving operating procedure, and shows the strong dependence of the nature of the sample (matrix effect) and its impact the uncertainty of results when a sample is applied to a non adequate procedure. The results suggest that an operational procedure produced of a validated method with controls performance established a priori and implemented during driving tests represents the traceability test.

Referências Bibliográficas

1. Bahia Filho O, Prada PR, Meneghesso C, Lanças FM. Desvendando a medição nos ensaios químicos: 1. A curva analítica ou de calibração. Scientia Chromatographica 2011; 3(3):251-261. http://dx.doi. org/10.4322/sc.2011.015

2. Instituto Nacional de Metrologia, Qualidade e Tecnologia – INMETRO. Vocabulário Internacional de Metrologia: conceitos fundamentais e gerais e termos associados (VIM 2012). Luso-Brasileira. Duque de Caxias: INMETRO, 2012.

3. Valcarcel M, Rios A. Traceability in chemical measurements for the end users. Trac-Trends in Analytical Chemistry 1999; 18(9-10.

4. King B. Meeting ISO/IEC 17025 traceability requirements – A new guide with worked examples. Accreditation and Quality Assurance 2003; 8(7-8):380‑382.

5. Armishaw P, King B, Millar RG. Achieving traceability in chemical measurement – a metrological approach to proficiency testing. Accreditation and Quality Assurance 2003; 8(5).

6. Priel M, Amarouche S, Fisicaro P. Metrological traceability is not always a straight line. Accreditation and Quality Assurance 2009; 14(11):593-599. http:// dx.doi.org/10.1007/s00769-009-0540-9

7. Thompson M. Traceability in perspective. Accreditation and Quality Assurance 2012; 17(3):353‑354. http:// dx.doi.org/10.1007/s00769-011-0866-y

8. Koeber R, Linsinger TPJ, Emons H. An approach for more precise statements of metrological traceability on reference material certificates. Accreditation and Quality Assurance 2010; 15(4):255-262. http://dx.doi. org/10.1007/s00769-010-0644-2

9. Bich W. Interdependence between measurement uncertainty and metrological traceability. Accreditation and Quality Assurance 2009; 14(11):581-586. http:// dx.doi.org/10.1007/s00769-009-0500-4

10. De Bievre P. Traceability is not meant to reduce uncertainty. Accreditation and Quality Assurance 2003; 8(11):497-497. http://dx.doi. org/10.1007/s00769-003-0704-y

11. Barros Neto BB, Scarminio IS, Bruns RE. Planejamento e otimização de experimentos. Campinas: Unicamp; 1995. 278 p. PMid:7584822.

12. Kaarls R, Milton MJT. Metrology in chemistry: considerations, approaches and developments on the applicability of methods of ‘higher order’. Comptes Rendus Physique 2004; 5(8):907-920.

13. 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.

14. Agência Nacional de Vigilância Sanitária – ANVISA. Resolução RE nº 899, de 29 de maio de 2003. Guia para validação de métodos analíticos e bioanalíticos. Diário Oficial da República Federativa do Brasil, Brasília, DF, 02 jun. 2003.

15. Bahia Filho O, Prada PR, Xavier C, Lancas FM. O significado da estimativa da incerteza na determinação de resíduos usando métodos cromatográficos. In: Livro de resumos do Simpósio Brasileiro de Cromatografia e Técnicas Afins – SIMCRO; 2010; Campos do Jordão. Campos do Jordão; 2010.