Selenium speciation by HPLC with tandem mass spectrometric detection

• Published in: Analytical and bioanalytical chemistry 2002-02, Vol.372 (3), p.486-490
• Main Authors: Lindemann, Torsten, Hintelmann, Holger
• Format: Article
• Language: English
• Subjects: Chromatography, High Pressure Liquid; Organoselenium Compounds - analysis; Spectrometry, Mass, Electrospray Ionization
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-001-1113-x

An HPLC/MS-MS method was developed for the analysis of selenium species. Tandem mass spectrometry (MS-MS) was chosen as a detector to provide structural and molecular information allowing the identification of species, which are not commercially available as standards. A new separation method for selenium species was developed, based on porous graphitic carbon (PGC) as the stationary phase. The applicability of the optimized HPLC/MS-MS system was demonstrated by the analysis of a mixture containing Se-methyl-selenocysteine, selenomethionine, selenocystine, selenoethionine and selenocystamine. All peaks were baseline-resolved and eluted within 16 min. Positive ionization led to higher intensities than negative ionization. Signal suppression tests showed that electrospray ionization (ESI) is a more effective ionization method than atmospheric pressure chemical ionization (APCI) for selenium species in a matrix containing pentafluoropropionic acid, heptafluorobutyric acid or ammonium formate. Comparative experiments with a triple quadrupole mass spectrometer (Quattro LC) and a time-of-flight instrument (Q-Tof-2) showed a 20 fold higher mass resolution of the latter mass spectrometer (m/Am= 5000) and significantly lower intensities for analyte signals as well as background noise compared to the triple quadrupole instrument. MS-MS spectra of the investigated selenium species including characteristic fragmentation patterns are presented.