[en] The Pickup and Mc Pherson isotope dilution theory has been applied to the twin-ion mass fragmentometric quantification of 5α-androstanediol di-trimethylsilyl ethers. The influence of the interference between the natural and the labeled compounds at the selected masses is discussed for four examples using different ²H synthesized molecules. It appears that the carrier-internal standard and the sample interferences are critical. In a reference method where high accuracy is required, the functions of internal standard and carrier must be allocated to two different molecules: a labeled analog (carrier) and a non labeled homolog (internal standard), so that the quantification of a well-defined sample may be carried out by single ion detection. (Auth,.)