title: Zero Volt Paper Spray Ionization and Its Mechanism.
abstract: The analytical performance and a suggested mechanism for zero volt paper spray using chromatography paper are presented. A spray is generated by the action of the pneumatic force of the mass spectrometer (MS) vacuum at the inlet. Positive and negative ion signals are observed, and comparisons are made with standard kV paper spray (PS) ionization and nanoelectrospray ionization (nESI). While the range of analytes to which zero volt PS is applicable is very similar to kV PS and nESI, differences in the mass spectra of mixtures are interpreted in terms of the more significant effects of analyte surface activity in the gentler zero volt experiment than in the other methods due to the significantly lower charge. The signal intensity of zero volt PS is also lower than in the other methods. A Monte Carlo simulation based on statistical fluctuation of positive and negative ions in solution has been implemented to explain the production of ions from initially uncharged droplets. Uncharged droplets first break up due to aerodynamics forces until they are in the 2-4 μm size range and then undergo Coulombic fission. A model involving statistical charge fluctuations in both phases predicts detection limits similar to those observed experimentally and explains the effects of binary mixture components on relative ionization efficiencies. The proposed mechanism may also play a role in ionization by other voltage-free methods.
authors.affiliation: †Department of Chemistry and Center for Analytical Instrumentation Development, Purdue University, West Lafayette, Indiana 47907, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Wleklinski
authors.affiliation: †Department of Chemistry and Center for Analytical Instrumentation Development, Purdue University, West Lafayette, Indiana 47907, United States.
authors.forename: Yafeng
authors.initials: Y
authors.lastname: Li
authors.affiliation: †Department of Chemistry and Center for Analytical Instrumentation Development, Purdue University, West Lafayette, Indiana 47907, United States.
authors.forename: Soumabha
authors.initials: S
authors.lastname: Bag
authors.affiliation: ‡DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600 036, India.
authors.forename: Depanjan
authors.initials: D
authors.lastname: Sarkar
authors.affiliation: ‡DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600 036, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Narayanan
authors.affiliation: ‡DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600 036, India.
authors.forename: T
authors.initials: T
authors.lastname: Pradeep
authors.affiliation: †Department of Chemistry and Center for Analytical Instrumentation Development, Purdue University, West Lafayette, Indiana 47907, United States.
authors.forename: R Graham
authors.initials: RG
authors.lastname: Cooks