The isotope ratio measurement techniquestotal evaporation (TE), modified total evaporation (MTE), and conventional-used for characterization measurements of certified reference materials by thermal ionization mass spectrometer instruments are compared. The advantages of each method, the fractionation profiles resulting from the measurement techniques, and factors affecting systematic components of bias in the isotope ratio measurements are discussed. The TE and MTE techniques yield major ratios and the conventional and MTE techniques yield minor ratios of comparable quality (in terms of precision and accuracy).