Ichiro Kudaka

Observation of triply charged metal ion clusters by electrospray and laser spray

Studies of the gas phase ion chemistry of triply charged metal ions, M(3+) = Sc(3+), Y(3+), La(3+), Ce(3+), and Yb(3+), were made by electrospray and laser spray. Triply charged ion ligand complexes, M(3+)(ligand)(n) were produced in the gas phase by electrospray and laser spray for the following ligands; glucose; sucrose; raffinose; cyclodextrin; ginsenoside Rb(1); dimethyl sulfoxide (DMSO) and hexamethylphosphoramide (HMPA). The ion evaporation mechanism must be invoked to explain the transfer of more surface active ions (e.g., NH(4)(+)(H(2)O)(n)) in solution to the gas phase, while the transfer of low surface active ions (e.g., La(3+)(sucrose)(n)) may be explained by the charged residue model. In general, the laser spray gives stronger ion signals than electrospray for aqueous and water/methanol solutions. The laser spray is found to be more suitable for the observation of ions with larger solvation energies (e.g., Sc(3+)(DMSO)(n)). These results may be due to the enrichment of the sample concentration by the selective vaporization of the volatile solvent on the tip of the stainless steel capillary and also to the finer droplet formation caused by the laser irradiation. Copyright 1999 John Wiley & Sons, Ltd.

Gas-phase solvation of CH+5 with H2

Abstract Thermochemical data, Δ H 0 n−1,n and Δ S 0 n−1,n , for the clustering reactions CH + 5 (H 2 ) n−1 + 2H 2 = CH + 5 (H 2 ) n + H 2 with n = 1–4 were measured using a pulsed electron-beam mass spectrometer. The binding energies of the clusters CH + 2 (H 2 ) n were smaller than 2 kcal/mol. The cluster CH + 5 (H 2 ) n with n =2 was found to be slightly more stable than those with n ⩾3, in accord with the most stable C S structure of CH + 5 predicted by MP2/6-31 G** geometry optimizations.

A comparative study of laser spray and electrospray

A comparative study of electrospray and laser spray has been undertaken from various aspects. In general, laser spray gave stronger ion signals than electrospray, for solutions with the sample concentration of </=10(-5)M. For an aqueous solution of arginine, ion intensities of the cluster ions H(+)(arginine)(n) with larger n were observed by laser spray than by electrospray. This may be due to the enrichment of the sample concentration by the selective vaporization of the solvent from the meniscus of the sample solution effusing out of the stainless steel capillary by the laser irradiation. For an H(2)O/CH(3)OH (1:1, v/v) solution of 10(-5) M Arg-Lys-Arg-Ala-Arg-Lys-Glu, laser spray gave stronger ion signals than electrospray while the most highly charged ion observed was [M + 4H](4+) for laser spray and [M + 5H](5+) for electrospray. Laser spray was found to be the most suitable for the analyses of aqueous solutions. Copyright 2000 John Wiley & Sons, Ltd.

A charge transfer complex CH+3—Ar in the gas phase

Abstract The thermochemical data Δ H 0 n −1, n and Δ S 0 n −1, n for clustering reactions CH + 3 (Ar) n −1 + Ar⇌CH + 3 (Ar) n were determined with a pulsed electron beam high-pressure mass spectrometer. It was found that (1) the bond energy of CH + 3 (Ar) n with n = 1 (−Δ H 0 0,1 = 11.3 kcal/mol) is much higher than that with n = 2 (−ΔH 0 1,2 = 2.26 kcal/mol); (2) −Δ H 0 1,2 is slightly greater than −Δ H 0 2,3 (1.97 kcal/mol), and (3) the −Δ H 0 n −1, n values with n = 3−8 are almost n -independent. The structures of CH + 3 (Ar) n with n = 1−3 were determined by ab initio MO calculations. The theoretical calculations predict some participation of covalent bond (charge transfer) in CH + 3 (Ar) n with n = 1 and 2. The nature of bonding in the complex with n ⩾ 3 is almost entirely electrostatic.

Electric field assisted thermal desorption ionization using an infrared laser

A new technique has been developed for the formation of gas-phase electrons and ions by electric field assisted thermal desorption ionization at atmospheric pressure. Experiments were carried out using a sharp tungsten wire tip coated with a thin solid sample film which was irradiated by a 10.6 µm infrared laser. By applying a strong electric field on the laser-irradiated tungsten wire tip, abundant ions such as alkali ions, halide ions, and also multiply charged negative ions S(2)O(6)(2-) and S(2)O(8)(2-), were formed. Copyright 1999 John Wiley & Sons, Ltd.