title: Complementary molecular and elemental detection of speciated thioarsenicals using ESI-MS in combination with a xenon-based collision-cell ICP-MS with application to fortified NIST freeze-dried urine.
abstract: The simultaneous detection of arsenic and sulfur in thioarsenicals was achieved using xenon-based collision-cell inductively coupled plasma (ICP) mass spectrometry (MS) in combination with high-performance liquid chromatography. In an attempt to minimize the (16)O(16)O(+) interference at m/z 32, both sample introduction and collision-cell experimental parameters were optimized. Low flow rates (0.25 mL/min) and a high methanol concentration (8%) in the mobile phase produced a fourfold decrease in the m/z 32 background. A plasma sampling depth change from 3 to 7 mm produced a twofold decrease in background at m/z 32, with a corresponding fourfold increase in the signal associated with a high ionization surrogate for sulfur. The quadrupole bias and the octopole bias were used as a kinetic energy discriminator between background and analyte ions, but a variety of tuning conditions produced similar (less than twofold change) detection limits for sulfur ((32)S). A 34-fold improvement in the (32)S detection limit was achieved using xenon instead of helium as a collision gas. The optimized xenon-based collision cell ICP mass spectrometer was then used with electrospray ionization MS to provide elemental and molecular-based information for the analysis of a fortified sample of NIST freeze-dried urine. The 3sigma detection limits, based on peak height for dimethylthioarsinic acid (DMTA) and trimethylarsine sulfide (TMAS), were 15 and 12 ng/g, respectively. Finally, the peak area reproducibilities (percentage relative standard deviation) of a 5-ppm fortified sample of NIST freeze dried urine for DMTA and TMAS were 7.4 and 5.4%, respectively.
authors.affiliation: Chemistry Department, University of Cincinnati, Cincinnati, OH 45221, USA.
authors.forename: Jenny L
authors.initials: JL
authors.lastname: Ellis
authors.forename: Sean D
authors.initials: SD
authors.lastname: Conklin
authors.forename: Christina M
authors.initials: CM
authors.lastname: Gallawa
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Kubachka
authors.forename: Andrea R
authors.initials: AR
authors.lastname: Young
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Creed
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Caruso
authors.forename: John T
authors.initials: JT
authors.lastname: Creed
mesh_terms: D001148:Arsenamide / Q000032:analysis*; D001151:Arsenic / Q000032:analysis; D001152:Arsenicals / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods; D005612:Freeze Drying; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods*; D013455:Sulfur / Q000032:analysis; D014556:Urine / Q000737:chemistry*; D014978:Xenon / Q000737:chemistry*
chemical_list: D001152:Arsenicals; D014978:Xenon; D013455:Sulfur; C009572:trimethylarsine; D001151:Arsenic; D001148:Arsenamide