title: The Kjeldahl method as a primary reference procedure for total protein in certified reference materials used in clinical chemistry. II. Selection of direct Kjeldahl analysis and its preliminary performance parameters.
abstract: To select a Kjeldahl procedure suitable for the determination of total protein in reference materials used in laboratory medicine, we reviewed in our previous article Kjeldahl methods adopted by clinical chemistry and found an indirect two-step analysis by total Kjeldahl nitrogen corrected for its nonprotein nitrogen and a direct analysis made on isolated protein precipitates. In this article, we compare both procedures on various reference materials. An indirect Kjeldahl method gave falsely lower results than a direct analysis. Preliminary performance parameters qualify the direct Kjeldahl analysis as a suitable primary reference procedure for the certification of total protein in reference laboratories.
authors.affiliation: a Department of Chemistry, Faculty of Science , Masaryk University , Brno , Czech Republic.
authors.forename: Bára
authors.initials: B
authors.lastname: Vinklárková
authors.forename: Vratislav
authors.initials: V
authors.lastname: Chromý
authors.forename: Luděk
authors.initials: L
authors.lastname: Šprongl
authors.forename: Miroslava
authors.initials: M
authors.lastname: Bittová
authors.forename: Milena
authors.initials: M
authors.lastname: Rikanová
authors.forename: Ivana
authors.initials: I
authors.lastname: Ohnútková
authors.forename: Lenka
authors.initials: L
authors.lastname: Žaludová
mesh_terms: D002624:Chemistry, Clinical / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D011506:Proteins / Q000737:chemistry*; D012016:Reference Values
chemical_list: D011506:Proteins
keywords: Kjeldahl method; serum-based reference materials; total protein