An isotopically labeled internal standard liquid chromatography-tandem mass spectrometry method for determination of ephedrine alkaloids and synephrine in dietary supplements.

We report a simplified analytical procedure for determination of ephedrine alkaloids and synephrine in dietary supplements. Cleanup by simple filtration, when combined with tandem mass spectrometry (MS/MS) detection, provided results comparable to our published method with solid phase extraction (SPE) cleanup and single-stage MS detection with in-source fragmentation. We also compared three mass spectrometric experimental configurations: electrospray (ESI) and atmospheric pressure chemical ionization (APCI) with MS/MS and APCI-MS with fragmentation provided by increasing cone voltage. Because these methods used one isotopically labeled internal standard to determine several different analytes, quantitation errors may arise from susceptibility to ionization suppression caused by the matrix. We therefore compared the results obtained by ESI and APCI ionization.