In targeted mass spectrometry, a transition pairs the mass-to-charge ratio of a precursor ion with that of one of its fragments. An unrelated compound can produce signal in the same channel if its ions match the monitored masses.
Braun and colleagues screened more than 150 pharmaceuticals and metabolites in a multisteroid LC–MS/MS method. They found that a naturally occurring heavier form of alpha-hydroxytriazolam, a triazolam metabolite, produced signals in transitions monitored for aldosterone. They also identified paroxetine as an interferent for a different steroid measurement.
The overlap occurred under the reported method conditions. Reviewing the chromatography, peak retention and the monitored transitions can help determine whether a suspicious signal belongs to the target compound. A method-specific interference warrants investigating the chromatogram and validation data before interpreting the reported hormone result.
Braun et al., study of nonsteroidal interferences in a multisteroid LC–MS/MS assay (full text) · DOI