Fitness for purpose in relation to specification limits

• Published in: Accreditation and quality assurance 2012-02, Vol.17 (1), p.27-34
• Main Authors: Alvarez-Prieto, Manuel, Jiménez-Chacón, Juan
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Biochemistry; Chemistry; Chemistry and Materials Science; Commercial Law; Compliance; Drinking water; Ecotoxicology; Fitness; Food Science; General Paper; Laboratories; Marketing; Mathematical analysis; Probability; Specifications; Uncertainty
• ISSN: 0949-1775; 1432-0517
• DOI: 10.1007/s00769-011-0825-7

Frequently, the ultimate goal of an analytical measurement is to assess compliance in respect to a specification limit. So, the necessary requirement is to make a correct decision on the grounds of the measurement result. It is suggested a practical methodology to attain fitness for purpose results when specification limits are established for compliance assessment. It is based on a comparison between fitness for purpose uncertainty functions that define a high probability of conclusive correct decisions and a characteristic uncertainty function which describes the performance of the analytical system along concentration in a given condition of measurement. To attain fitness for purpose results, different replication programs are applied. Determinations of Zn, Mn and Cd in potable water are discussed as case studies. They represent different cases concerning relative position of detection and specification limits. A definition of fitness for purpose when specification limits are relevant is given. Quality of analytical results and analytical procedures should be associated with the concept of fitness for purpose.