Utilizing the inherent electrolysis in a chip-based nanoelectrospray emitter system to facilitate selective ionization and mass spectrometric analysis of metallo alkylporphyrins

AbstractA commercially available chip-based infusion nanoelectrospray ionization system was used to ionize metallo alkylporphyrins for mass spectrometric detection and structure elucidation by mass spectrometry. Different ionic forms of model compounds (nickel (II), vanadyl (II), copper (II), and cobalt (II) octaethylporphyrin) were created by using two different types of conductive pipette tips supplied with the device. These pipette tips provide the conductive contact to solution at which the electrolysis process inherent to electrospray takes places in the device. The original unmodified, bare carbon-impregnated plastic pipette tips were exploited to intentionally electrochemically oxidize (ionize) the porphyrins to form molecular radical cations for detection. Use of modified pipette tips, with a surface coating devised to inhibit analyte mass transport to the surface or slow the kinetics of the analyte electrochemical reactions, was shown to limit the ionic species observed in the mass spectra of these porphyrins largely, but not exclusively, to the protonated molecule. Under the conditions of these experiments, the effective upper potential limit for oxidation with the uncoated pipette tip was 1.1 V or less, and the coated pipette tips effectively prevented the oxidation of analytes with redox potentials greater than about 0.25 V. Product ion spectra of either molecular ionic species could be used to determine the alkyl chain length on the porphyrin macrocycle. The utility of this electrochemical ionization approach for the analysis of naturally occurring samples was demonstrated using nickel geoporphyrin fractions isolated from Gilsonite bitumen. Acquiring neutral loss spectra as a means to improve the specificity of detection in these complex natural samples was also illustrated. FigureCross sectional view of the chip-based nanoESI device used for selective ionization of metallo alkylporphyrins

[1]  G. V. Van Berkel,et al.  Redox buffering in an electrospray ion source using a copper capillary emitter. , 2001, Journal of mass spectrometry : JMS.

[2]  D. Heath,et al.  Determination of carotenoids and all-trans-retinol in fish eggs by liquid chromatography-electrospray ionization-tandem mass spectrometry. , 2005, Journal of chromatography. B, Analytical technologies in the biomedical and life sciences.

[3]  G. Glish,et al.  Electrochemical Origin of Radical Cations Observed in Electrospray Ionization Mass Spectra , 1992 .

[4]  G. J. Berkel,et al.  Observation of gas-phase molecular dications formed from neutral organics in solution via the controlled-current electrolytic process inherent to electrospray , 1996, Journal of the American Society for Mass Spectrometry.

[5]  H. Girault,et al.  Functional electrospray emitters. , 2009, The Analyst.

[6]  R. Martínez‐Álvarez,et al.  Electrospray mass spectra of group 6 (Fischer) carbenes in the presence of electron-donor compounds. , 2003, Journal of mass spectrometry : JMS.

[7]  H. Girault,et al.  On-line cysteine modification for protein analysis: new probes for electrochemical tagging nanospray mass spectrometry , 2004 .

[8]  G. J. Berkel,et al.  Electrospray as a controlled-current electrolytic cell: Electrochemical ionization of neutral analytes for detection by electrospray mass spectrometry , 1995 .

[9]  H. Girault,et al.  On‐line counting of cysteine residues in peptides during electrospray ionization by electrogenerated tags and their application to protein identification , 2005, Electrophoresis.

[10]  H. Girault,et al.  Mechanistic aspects of on-line electrochemical tagging of free L-cysteine residues during electrospray ionisation for mass spectrometry in protein analysis. , 2003, Chemphyschem : a European journal of chemical physics and physical chemistry.

[11]  Colleen K Van Pelt,et al.  Automated chip‐based nanoelectrospray‐mass spectrometry for rapid identification of proteins separated by two‐dimensional gel electrophoresis , 2003, Electrophoresis.

[12]  J. Josserand,et al.  Electrochemical multi-tagging of cysteinyl peptides during microspray mass spectrometry: numerical simulation of consecutive reactions in a microchannel. , 2005, Physical chemistry chemical physics : PCCP.

[13]  G. Eglinton,et al.  Petroporphyrins. I - Preliminary characterization of the porphyrins of gilsonite , 1979 .

[14]  P. Schnier,et al.  Electrochemical processes in a wire-in-a-capillary bulk-loaded, nano-electrospray emitter , 2001, Journal of the American Society for Mass Spectrometry.

[15]  E. Hoffmann.  Tandem mass spectrometry: A primer , 1996 .

[16]  R. Yost,et al.  Studies on high carbon number geoporphyrins by tandem mass spectrometry , 1989 .

[17]  J. Rossier,et al.  On-line electrochemical tagging of cysteines in proteins during nanospray , 2002 .

[18]  Liang Qiao,et al.  Electrochemical aspects of electrospray and laser desorption/ionization for mass spectrometry. , 2010, Annual review of analytical chemistry.

[19]  J. Quirke,et al.  Petroporphyrins—III: Characterisation of a c32 aetioporphyrin from gilsonite as the bis[porphyrinato-mercury(II) acetato]mercury(II) complex. Origin and significance , 1980 .

[20]  B. Stimpson,et al.  Electrohydrodynamic ionization mass spectrometry of biochemical materials. , 1978, Biomedical mass spectrometry.

[21]  P. Vainiotalo,et al.  Laccase-catalyzed mediated oxidation of benzyl alcohol: the role of TEMPO and formation of products including benzonitrile studied by nanoelectrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. , 2004, Journal of mass spectrometry : JMS.

[22]  R. Yost,et al.  Tandem mass spectrometry for characterization of high-carbon-number geoporphyrins , 1986 .

[23]  G. Eglinton,et al.  Petroporphyrins IV. Nuclear overhauser enhancement 1H NMR studies of deoxophylloerythroetio porphyrins from gilsonite , 1980 .

[24]  J. Josserand,et al.  Generation of mass tags by the inherent electrochemistry of electrospray for protein mass spectrometry , 2004, Journal of the American Society for Mass Spectrometry.

[25]  T. Covey,et al.  Automated nanospray using chip-based emitters for the quantitative analysis of pharmaceutical compounds , 2005, Journal of the American Society for Mass Spectrometry.

[26]  Pio Colepicolo,et al.  Balance of xanthophylls molecular and protonated molecular ions in electrospray ionization. , 2005, Journal of mass spectrometry : JMS.

[27]  D. Simons,et al.  Electrohydrodynamic ionization mass spectrometry - the ionization of liquid glycerol and non-volatile organic solutes , 1974 .

[28]  H. Girault,et al.  Probing cysteine reactivity in proteins by mass spectrometric EC-tagging. , 2006, Journal of proteome research.

[29]  G. V. Van Berkel,et al.  Using the electrochemistry of the electrospray ion source. , 2007, Analytical chemistry.

[30]  G. V. Berkel,et al.  Tabulation of exact masses and comparison of isotope patterns expected for geoporphyrin molecular ions in electron ionization mass spectra , 1991 .

[31]  P. Gates,et al.  New chemical evidence for the ability to generate radical molecular ions of polyenes from ESI and HR-MALDI mass spectrometry. , 2004, The Analyst.

[32]  J. Sugihara,et al.  Porphyrins in Gilsonite , 1957 .

[33]  G. Eglinton,et al.  Petroporphyrins. 1. Preliminary characterization of the porphyrins of gilsonite , 1979 .

[34]  V. Kertész,et al.  Electrochemistry of the Electrospray Ion Source , 2012 .

[35]  G. V. Van Berkel,et al.  Expanded electrochemical capabilities of the electrospray ion source using porous flow-through electrodes as the upstream ground and emitter high-voltage contact. , 2005, Analytical chemistry.

[36]  J. Klassen,et al.  Influence of solution and gas phase processes on protein-carbohydrate binding affinities determined by nanoelectrospray Fourier transform ion cyclotron resonance mass spectrometry. , 2003, Analytical chemistry.

[37]  H. Girault,et al.  Study of peptide on-line complexation with transition-metal ions generated from sacrificial electrodes in thin-chip polymer microsprays. , 2005, Rapid communications in mass spectrometry : RCM.

[38]  G. Siuzdak,et al.  Electrospray and MALDI mass spectrometry in the identification of spermicides in criminal investigations. , 1999, Journal of forensic sciences.

[39]  M L Hagmann,et al.  Characterization of the F(ab')2 fragment of a murine monoclonal antibody using capillary isoelectric focusing and electrospray ionization mass spectrometry. , 1998, Journal of chromatography. A.