title: An application of gas chromatography mass spectrometry to the quantitation of substances and their labelled variants.
abstract: A method is proposed for the quantitative estimation of a substance and its labelled analogue using the selected ion monitoring technique of gas chromatography mass spectrometry, in which estimation is achieved without a third labelled analogue as internal standard. In a first measurement the ratio of natural to labelled substance is established. Then a known amount of either labelled or natural compound is added, the isotope ratio is determined a second time and from these two measurements the mass amounts can be calculated. When applied to the heptafluorobutyrates of androstenedione and progesterone about 10 pg of 14C labeled compounds can be determined in the presence of 1 ng of the natural substances.
mesh_terms: D000735:Androstenedione / Q000032:analysis; D002849:Chromatography, Gas; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D011374:Progesterone / Q000032:analysis; D011868:Radioisotopes / Q000032:analysis*
chemical_list: D011868:Radioisotopes; D000735:Androstenedione; D011374:Progesterone