Measurement of trimethylamine and trimethylamine N-oxide independently in urine by fast atom bombardment mass spectrometry

We report a method based upon fast atom bombardment mass spectrometry (FAB- MS) and stable isotope dilution techniques for the measurement of urinary t rimethylamine (TMA) and trimethylamine N-oxide (TMAOx). TA is extracted fro m urine that was spiked with N-15-labeled TMA. The extracted TMA isotopomer s are quaternized with trideuteromethyl iodide and analyzed in FAB-MS with hexaethylene glycol as matrix. TMAOx is measured by evaporation of another sample of the urine spiked with N-15-labeled TMAOx on the FAB probe and ana lyzed as for the TMA. The method allows the ready and simple distinguishing of controls and patients with TMAuria, and is useful in monitoring patient s with the disorder. We give examples of its use in determining normal cont rol ranges for these metabolites and in evaluating patients. (C) 1999 Acade mic Press.