Mass spectrometric characterization of different norandrosterone derivatives by low-cost mass spectrometric detectors using electron ionization and chemical ionization.

The abuse of nortestosterone in sport is an important problem in doping-control analysis. In order to detect the main urinary metabolite of nortestosterone, norandrosterone (NA), sensitive and specific methodology is necessary. In this context the use of a low-cost mass spectrometric detector such as the Finnigan MAT ion-trap detector (ITD) was studied. The electron ionization (EI) and positive-ion chemical ionization (PICI) mass spectra of the methoxime-trimethylsilyl, trimethylsilyl-enol trimethylsilyl ether and pentafluoropropionic ester derivatives of NA are described. The limits of detection of these derivatives are compared with those obtained by the Hewlett-Packard mass selective detector (MSD), another low-cost mass spectrometric detector and operating only in the EI mode. For the derivatives of the reference standard of NA the ITD has in the EI mode the same limit of detection, in the range of 0.5 to 1 ng injected on the column, as the MSD. However, under these conditions the ITD provides more spectrometric information, because it gives full scan data. Moreover, with the same or even improved limits of detection the ITD can operate in the PICI mode. On the other hand, for the analysis of NA isolated from urine samples, the performance of the MSD was better than that of the ITD. The ion trapping technique is probably limited when the chemical background is high.