Final report on CCQM-K91: Key comparison on pH of an unknown phthalate buffer

Spitzer, Petra; Bastkowski, Frank; Adel, Beatrice; Dimitrova, Lyudmila; Gonzaga, Fabiano Barbieri; Jakobsen, Pt; Fisicaro, Paola; Stoica, Daniela; Asakai, Toshiaki; Maksimov, I; Szilágyi, Z N; Reyes, A. L.; Monroy, Mario Rodríguez; Canaza, G T; Kozlowski, Wladyslaw; Pawlina, Monika; Kutovoy, Viatcheslav; Vyskočil, L; Mathiasová, Anna; Nongluck, T; Ficicioglu, F; Gavrilkin, Vladimir; Pratt, Kenneth W.

doi:10.1088/0026-1394/50/1a/08016

Cited by 2 publications

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“…The recently completed CCQM-K91 (phthalate) [14] is the first KC of the second cycle and is not included in this study. CCQM-K91 and the other pH studies currently in progress or planned are designed as fresh root comparisons rather than maintaining linkages to the earlier studies.…”

Section: Sourcesmentioning

confidence: 99%

“Degrees of equivalence” for chemical measurement capabilities: primary pH

Duewer

Pratt

Cherdchu³

et al. 2014

Accred Qual Assur

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The key comparison (KC) studies of the Consultative Committee for Amount of Substance-Metrology in Chemistry help ensure the reliability of chemical and biochemical measurements relevant to international trade and environmental-, health-, and safety-related decision making. The traditional final evaluation of each measurement result reported by a KC participant is a ''degree of equivalence'' (DEq) that quantitatively specifies how consistent each individual result is relative to a reference value. Recognizing the impossibility of conducting separate KCs for all important analytes in all important sample matrices at all important analyte levels, emphasis is now shifting to documenting broadly applicable critical or ''core'' measurement competencies elicited through a series of studies. To better accomplish the necessary synthesis of results, data analysis and display tools must be developed for objectively and quantitatively combining individual DEqs. The information detailed in the 11 KCs of primary method pH measurements publically available as of 2013 provides an excellent ''best case'' prototype for such analysis. We here propose tools that enable documenting the expected primary pH measurement performance of individual participants between pH 1 and pH 11 and from 15°C to 37°C. These tools may prove useful for other areas where the uncertainty of measurement is a predictable function of the measured quantity, such as the stable gases. That results for relatively simple measurement processes can be combined using relatively simple analysis and display methods does not ensure that similarly meaningful summaries can be devised for less well understood and controlled systems, but it provides the incentive to attempt to do so.

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Section: Sourcesmentioning

confidence: 99%

“Degrees of equivalence” for chemical measurement capabilities: primary pH

Duewer

Pratt

Cherdchu³

et al. 2014

Accred Qual Assur

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Longitudinal meta-analysis of NIST pH Standard Reference Materials®: a complement to pH key comparisons

Pratt

2014

Anal Bioanal Chem

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This meta-analysis assesses the long-term (up to 70 years) within-laboratory variation of the NIST pH Standard Reference Material® (SRM) tetroxalate, phthalate, phosphate, borate, and carbonate buffers. Values of ΔpH(S), the difference between the certified pH value, pH(S), of each SRM issue and the mean of all pH(S) values for the given SRM at that Celsius temperature, t, are graphed as a function of the SRM issue and t. In most cases, |ΔpH(S)| < 0.004. Deviations from the nominal base:acid amount (mole) ratio of a buffer yield t-independent, constant shifts in ΔpH(S). The mean ΔpH(S) characterizes such deviations. The corresponding mole fraction of impurity in the conjugate buffer component is generally <0.3 %. Changes in the equipment, personnel, materials, and methodology of the pH(S) measurement yield t-dependent variations. The standard deviation of ΔpH(S) characterizes such changes. Standard deviations of ΔpH(S) are generally 0.0015 or less. The results provide a long-term, single-institution complement to the time-specific, multi-institution results of pH key comparisons administered by the Consultative Committee for Metrology in Chemistry and Biology (CCQM).

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Final report on CCQM-K91: Key comparison on pH of an unknown phthalate buffer

Cited by 2 publications

References 0 publications

“Degrees of equivalence” for chemical measurement capabilities: primary pH

“Degrees of equivalence” for chemical measurement capabilities: primary pH

Longitudinal meta-analysis of NIST pH Standard Reference Materials®: a complement to pH key comparisons

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