Primary methods of measurement in chemical analysis

Abstract

Primary methods of measurement have a central function in metrology. They are an essential component in the realisation of the SI units and therefore are indispensable for establishing traceability of measurements of all kinds of physical quantities to the corresponding SI units. This is also true for chemical analysis. Gravimetry, titrimetry, coulometry, and isotope dilution mass spectrometry (IDMS) are evaluated with regard to their potential to be primary methods according to a general definition of primary methods recently given by the Comité Consultatif pour la Quantité de Matière (CCQM). Optical absorption spectrometry and methods based on colligative properties are also considered. A general scheme for establishing traceability of chemical measurements to the SI units using primary methods is discussed.

International Association of Geoanalysts' Protocol for the Certification of Geological and Environmental Reference Materials: A Supplement

“…Method of measurement: the logical sequence of operations described generically, used in the performance of measurements. (VIM (1995), section 2.4) Methods of measurement have often been classified as definitive/primary (Uriano and Gravatt 1977, ISO 1989, Richter 1997 or comparative, depending on whether measurements are made directly or indirectly in terms of base SI units, or whether measurements are based on comparison of the signal from the measured physical property between samples and calibration standards. The comparative method may, or may not be, a reference (or technical standard) method.…”

“…Note that the ISO Guide definition of definitive method differs somewhat from that given originally in the International Vocabulary of Basic and General Terms in Metrology (1984). Note also that the more recent terminology refers to such methods as primary methods (Papadakis et al 1997, Richter 1997. The most recent Comite Consultatif pour la Quantite de Matiere (CCQM) definition follows.…”

Zastosowanie metody ISM-SAM do oznaczania pierwiastków śladowych w oleju napędowym

“…Dla metody takiej zdefiniowano i udokumentowano wartości niepewności w odniesieniu do jednostek SI. Wyniki uzyskane za pomocą techniki pierwotnej są akceptowane bez konieczności zastosowania metody odniesienia [12,13]. Do metod pierwotnych zalicza się spektrometrię mas z plazmą indukcyjnie sprzężoną rozcieńczenia izotopowego (ID ICP MS).…”

ISO Best Practices in Reference Material Certification and Use in Geoanalysis

“…However, the absence of bias may be theoretical rather than actual (e.g., Fassett and Paulsen 1989). Even definitive methods (Heumann 1988, Richter 1997 can be carried out incorrectly unless great care is taken to avoid that possibility. In any such instances, the definitive method will produce biased results, despite the potential to produce the highest achievable metrological quality of the result.…”

“…Differences exist between results of different methods, because few methods are entirely free from any bias. Even primary or definitive methods (Papadakis et al 1997, Richter 1997) that can be theoretically bias-free often are applied incorrectly, so that bias nonetheless appears in the result. Chemical decomposition and separation may be incomplete; background and spectral interference corrections may either have been overlooked or may be incomplete.…”