A high-accuracy method of analysis of 19-norandrosterone in human urine as utilised for the international laboratory intercomparison CCQM-P68

A high-accuracy exact-matching isotope dilution mass spectrometry (IDMS) method for 19-norandrosterone (19-NA) in human urine was developed at NMIA for the certification of a freeze-dried human urine reference material (CRM NMIA MX002). The method utilised GC/HRMS analysis following hydrolysis, solvent extraction, HPLC fractionation and derivatisation. The method development included investigation of all potential analytical biases for the different stages of the method and included development of a confirmatory LC/MS/MS method. The measurement uncertainty of the reference method was rigorously investigated with the achieved expanded uncertainty being less than 4% at the 95% level of confidence. The method was used in the Comité Consultatif pour la Quantité de Matière (CCQM) pilot study CCQM-P68 which was an interlaboratory intercomparison for the analysis of 19-NA in human urine in which four national metrology institutes (NMIs) participated in. The agreement in the results from the NMIA method with those from the other NMIs was excellent.