Identification of Metal Cations, Metal Complexes, and Anions by Electrospray Mass Spectrometry in the Negative Ion Mode

Self Cite

M(NO 3 ) xϪ ions are generated by electrospray ionization (ESI) of metal solutions in nitric acid in negative ion mode. Collision-induced reactions of these ions are monitored in a tandem mass spectrometer (MS) of quadrupole-octopole-quadrupole (QoQ) geometry. For Group 1and 2 elements, the M(NO 3 ) x Ϫ ions dissociate into NO 3 Ϫ and neutral metal nitrate molecules. These elements also form some M x (NO 3 ) xϩ1 Ϫ clusters, especially Li ϩ . Metal nitrate ions from transition elements and Group 13 elements fragment into oxo products and also undergo internal electron transfer to leave the M atom in a lower oxidation state. To calibrate the collision energy, the dissociation energy of O-NO 2 Ϫ is found to be 5.55 eV, about 0.76 eV lower than a value derived from thermochemistry. Most studies of small inorganic ions have been done in positive ion mode [14 -18]. Many metal-solvent clusters, e.g., M xϩ (H 2 O) n , n ϭ 1 to 6, are typically formed under "soft" ion extraction conditions [7,17,18]. Highly charged metal ions tend to react with solvent molecules to yield hydroxy or methoxy ions when energetic collision conditions are used to remove solvent during ion extraction. Preserving the original form of the metal ion in positive mode generally requires element-specific optimization of ion extraction conditions and leads to a variety of ion-solvent clusters.Previous work from our group [19] showed that an excess of nitric acid can be used to produce M(NO 3 ) x Ϫ ions in negative ion mode. A single set of ion extraction conditions yields these ions for many elements. This early work was done with only one stage of MS. The present work reports collision-induced dissociation (CID) reactions of these M(NO 3 ) x Ϫ ions in a triple "quadrupole" MS, actually a QoQ instrument. Experimental Samples and Sample PreparationConcentrated nitric acid was purchased from J. T. Baker (Phillipsburg, NJ) and used without further purification. Aliquots of the concentrated acid were mixed with HPLC grade methanol and deionized water (18 M⍀, Barnstead Nanopure, Newton, MA) to form a solvent of 0.05% nitric acid in 25% water:75% methanol. Aliquots of aqueous, acidic metal stock solutions (1000 ppm, Spex Certiprep, Metuchen, NJ ) were diluted with solvent to the desired concentrations.

Section: Ms and Cid Of Nitrate Complexes Of Group 1 And 2 Metalssupporting

confidence: 68%

Section: M(no 3 ) Xmentioning

confidence: 99%

mentioning

confidence: 99%

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Tandem mass spectrometry of metal nitrate negative ions produced by electrospray ionization

Byers

Houk

2003

Self Cite

“…Alkali and transition-metal cations are known to form complexes with nitrate when an excess of NO 3 Ϫ is present in solution [42,43]. Generally, these complexes are of the form [(UO 2 )(NO 3 ) m ] Ϫ (m ϭ 1-3), although the formation of oxo-nitrate ([(UO 2 )(O)(NO 3 ) m ] Ϫ (m ϭ 1-2) and hydroxy-nitrate ([(UO 2 )(OH) n (NO 3 ) m ] Ϫ (n ϭ 1-2, m ϭ 0 -1) products are also observed [43].…”

Section: Negative Ions Containing Uranyl and Nitrate Generated By Esimentioning

confidence: 99%

Ions generated from uranyl nitrate solutions by electrospray ionization (ESI) and detected with fourier transform ion-cyclotron resonance (FT-ICR) mass spectrometry

Pasilis

Somogyi

Herrmann

et al. 2006

Electrospray ionization (ESI) of uranyl nitrate solutions generates a wide variety of positively and negatively charged ions, including complex adducts of uranyl ions with methoxy, hydroxy, and nitrate ligands. In the positive ion mode, ions detected by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry are sensitive to instrumental tuning parameters such as quadrupole operating frequency and trapping time. Positive ions correspond to oligomeric uranyl nitrate species that can be characterized as having a general formula of

“…Moreover, negative ionization is more susceptible to corona discharge [21,22]. Therefore, negative-ion mode MS detection of noncovalent anion-receptor complexes is less common than positive-ion mode, with the examples reported [23][24][25][26][27][28] for the detection of organic explosives. APCI presents some advantages compared with ESI in quantitative analysis such as higher dynamic range, and is considered rugged, easy to operate, and more tolerant of higher buffer concentrations (fewer matrix effects) [31].…”

mentioning

confidence: 99%

Identification of Anionic Supramolecular Complexes of Sulfonamide Receptors with Cl⁻, NO₃⁻, Br⁻, and I⁻ by APCI-MS

Kavallieratos

Sabucedo

Pau

et al. 2005

As part of a mass spectrometric investigation of the binding properties of sulfonamide anion receptors, an atmospheric pressure chemical ionization mass spectrometric (APCI-MS) method involving direct infusion followed by thermal desorption was employed for identification of anionic supramolecular complexes in dichloromethane (CH 2 Cl 2 ). Specifically, the dansylamide derivative of tris(2-aminoethyl)amine (tren) (1), the chiral 1,3-benzenesulfonamide derivatives of (1R,2S)-(ϩ)-cis-1-amino-2-indanol (2), and (R)-(ϩ)-bornylamine, (3), were shown to bind halide and nitrate ions in the presence of (nϪBu) Solutions of receptors and anions in CH 2 Cl 2 were combined to form the anionic supramolecular complexes, which were subsequently introduced into the mass spectrometer via direct infusion followed by thermal desorption. The anionic supramolecular complexes Inorganic ions with small mass-to-charge ratios are typically analyzed by other techniques, such as ion chromatography and capillary electrophoresis, because under normal MS ionization conditions many compounds can produce small ions that can interfere with their detection. There are, however, some notable examples [7,8] that demonstrate the potential of soft ionization methods [9], such as atmospheric pressure chemical ionization mass spectrometry (APCI-MS) and electrospray ionization mass spectrometry (ESI-MS)[10] for analysis of inorganic ions, and ion pairs, such as ammonium nitrate [11].Increased sensitivity for MS analysis of inorganic ions has been achieved by a relatively new and promising strategy, which bridges the fields of mass spectrometry and supramolecular chemistry [12][13][14]. This approach is based on selective host molecules for specific cationic or anionic guests, which can form ionic adducts with higher molecular mass. Most of the supramolecular complexes investigated by MS involve macrocycles, such as crown ethers and cryptands, which form cationic metal-receptor complexes detectable in positive ion mode [15][16][17][18][19]. Anion supramolecular chemistry [20] is relatively less well developed and oftentimes anion receptors are not as strong as cation receptors in terms of thermodynamic binding constants. Moreover, negative ionization is more susceptible to corona discharge [21,22]. Therefore, negative-ion mode MS detection of noncovalent anion-receptor complexes is less common than positive-ion mode, with the examples reported [23][24][25][26][27][28] for the detection of organic explosives. APCI presents some advantages compared with ESI in quantitative analysis such as higher dynamic range, and is considered rugged, easy to operate, and more tolerant of higher buffer concentrations (fewer matrix effects) [31]. Multiply charged species are typically not observed in APCI-MS spectra [1]. Even though APCI is considered a soft ionization method, it has not found the same application in anion supramolecular chemistry as ESI because the larger supramolecular ions are generally not observed. Therefore, successful identification of noncova...