Loading in 2 Seconds...
Loading in 2 Seconds...
Investigation of Oxidative and Conjugative Metabolism Reactions with Liquid Chromatography / AccurateMass High Resolution Mass Spectrometry Maciej Bromirski Thermo Fisher Scientific (Bremen, Germany) Denver, June 8, 2011
Why? • In metabolic studies, the identification of metabolites in blood or urine samples as well as liver microsome incubations is relatively easy, but the detection of reactive species turns out to be tricky • Trapping experiments deliver only indirect proof of identitiy • Electrochemical simulations of metabolic processes, coupled to high performance liquid chromatography (HPLC), have been shown to be a simple and fast alternative to classical approaches • Combination of electrochemistry with high resolution accurate mass (HRAM) mass spectrometry may deliver enhanced sensitivity and confidence in metabolite detection, especially for reactive metabolites
Experimental Setup • For the shown experiments a ROXY™ potentiostat equipped with a Reactor Cell™ thin layer flowcell from Antec B. V. (Zoeterwoude, The Netherlands) was used, coupled to a Thermo Scientific Exactive Benchtop Orbitrap mass spectrometer • Analyte solutions were provided in water / acetonitrile 1:1 with 0.1% formic acid • Protein solutions for conjugation experiments were provided in 10 mM ammonium formiate solution, adjusted to pH 7.8
Infusion experiments for Phase I and Phase II studies only analyte passing EC cell is analysed Phase I studies conjugation of reaction products with protein after EC cell Phase II studies
Setup with chromatographic separation reaction products are trapped in injection loop content of injection loop is passed to column
Exactive™ - specification • Resolution • 100,000 at 1 scan per second • 10,000 at 10 scans per second • Mass accuracy • ppm mass accuracy • Sensitivity • 500 fg Buspirone > 10:1 • Dynamic Range • >4000 within a spectrum • Scan speed • Up to 10 scans per second • Mass Range • m/z 50 - 4000 • Polarity switching • Yes, 1 full cycle <1 sec
Reaction products of Thiamethoxam C8H11ON4ClS Thiamethoxam C8H10O3N5ClS C8H12O3N4S C7H13O5N3 C8H12O1N5ClS C8H10O2N5ClS C8H10O2N4S -H2? +O C8H10O4N5ClS C8H11O5N5S
Voltammogram of selected reaction products Thiamethoxam M1 m/z 308 M2 m/z 290 M3 m/z 276 M4 m/z 262 M5 m/z 247 M6 m/z 245 M7 m/z 230
... but what else is it??? • Dehydrogenated Thiamethoxam: C8H8O3N5ClS • exact mass 290.01091 • Measured mass: 290.05487 • on an Exactive, this is a clear mismatch • Proposed elemental composition: C8H11O5N5S • Proposed structure:
Reaction products of Ticlopidin 0.0 V EC potential 2.5 V EC potential
Metabolites confirmed by microsome incubation1 • 264.0594: Ticlopidin • 262.0441: Ticlopidin – 2H • 260.0290: Ticlopidin – 4H • 278.0390: Ticlopidin – 2H + O • 280.0544: Ticlopidin + O 1 Davie et al., DMD 32:49–57, 2004
A closer look on the oxygenation products C14H12ONClS Ticlopidin – 2H +O Δm 1.3 ppm C14H14ONClS Ticlopidin +O Δm 1.1 ppm
Summary • Metabolites can be detected with high sensitivity and specificity • Ultra high resolution provides clear separation from interferences • Unique scan-to-scan mass accuracy provides clear distinction of false positives from correct signals • High confidence in identification is provided
Acknowlegements • Antec B. V., Zouterwoude, The Netherlands • Agnieszka Kraj • University of Muenster, Germany • Uwe Karst • Anne Baumann • Thorsten Vielhaber • Thermo Fisher Scientific, Germany • Olaf Scheibner