title: Sensitivity and selectivity of switchable reagent ion soft chemical ionization mass spectrometry for the detection of picric acid.
abstract: We have investigated the reactions of NO(+), H3O(+), O2(+), and Kr(+) with picric acid (2,4,6 trinitrophenol, C6H3N3O7, PiA) using a time-of-flight mass spectrometer with a switchable reagent ion source. NO(+) forms a simple adduct ion PiA·NO(+), while H3O(+) reacts with PiA via nondissociative proton transfer to form PiAH(+). In contrast, both O2(+) and Kr(+) react with PiA by nondissociative charge transfer to produce PiA(+). For Kr(+), we also observe dissociation of PiA, producing NO2(+) with a branching percentage of approximately 40%. For the reagent ions H3O(+) and O2(+) (and operating the drift tube with normal laboratory air), we find that the intensities of the PiAH(+) and PiA(+) ions both exhibit a peak at a given drift-tube voltage (which is humidity dependent). This unusual behavior implies a peak in the detection sensitivity of PiA as a function of the drift-tube voltage (and hence E/N). Aided by electronic-structure calculations and our previous studies of trinitrotoluene and trinitrobenzene, we provide a possible explanation for the observed peak in the detection sensitivity of PiA.
authors.affiliation: IONICON Analytik Gesellschaft m.b.H. , Eduard-Bodem-Gasse 3, A-6020 Innsbruck, Austria.
authors.forename: Bishu
authors.initials: B
authors.lastname: Agarwal
authors.forename: Ramón
authors.initials: R
authors.lastname: González-Méndez
authors.forename: Matteo
authors.initials: M
authors.lastname: Lanza
authors.forename: Philipp
authors.initials: P
authors.lastname: Sulzer
authors.forename: Tilmann D
authors.initials: TD
authors.lastname: Märk
authors.forename: Neil
authors.initials: N
authors.lastname: Thomas
authors.forename: Chris A
authors.initials: CA
authors.lastname: Mayhew
mesh_terms: D007202:Indicators and Reagents / Q000737:chemistry; D007726:Krypton / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D009569:Nitric Oxide / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D010851:Picrates / Q000032:analysis* / Q000737:chemistry; D011789:Quantum Theory; D014867:Water / Q000737:chemistry
chemical_list: D007202:Indicators and Reagents; D010851:Picrates; D014867:Water; D009569:Nitric Oxide; D007726:Krypton; C005858:picric acid; D010100:Oxygen