In accomplishing successful electrospray ionization analyses, it is imperative to have an understanding of the effects of variables such as analyte structure, instrumental parameters, and solution composition. Here, we review some fundamental studies of the ESI process that are relevant to these issues. We discuss how analyte chargeability and surface activity are related to ESI response, and how accessible parameters such as nonpolar surface area and reversed phase HPLC retention time can be used to predict relative ESI response. Also presented is a description of how derivitizing agents can be used to maximize or enable ESI response by improving the chargeability or hydrophobicity of ESI analytes. Limiting factors in the ESI calibration curve are discussed. At high concentrations, these factors include droplet surface area and excess charge concentration, whereas at low concentrations ion transmission becomes an issue, and chemical interference can also be limiting. Stable and reproducible non-pneumatic ESI operation depends on the ability to balance a number of parameters, including applied voltage and solution surface tension, flow rate, and conductivity. We discuss how changing these parameters can shift the mode of ESI operation from stable to unstable, and how current-voltage curves can be used to characterize the mode of ESI operation. Finally, the characteristics of the ideal ESI solvent, including surface tension and conductivity requirements, are discussed. Analysis in the positive ion mode can be accomplished with acidified methanol/water solutions, but negative ion mode analysis necessitates special constituents that suppress corona discharge and facilitate the production of stable negative ions.

Practical implications of some recent studies in electrospray ionization fundamentals.

Electrospray ionization mass spectrometry has been used to study protein interactions driven by noncovalent forces The gentleness of the electrospray ionization process allows intact protein complexes to be directly detected by mass spectrometry Evidence from the growing body of literature suggests that the ESI-MS observations for these weakly bound systems reflect, to some extent, the nature of the interaction found in the condensed phase Stoichiometry of the complex can be easily obtained from the resulting mass spectrum because the molecular weight of the complex is directly measured For the study of protein interactions, ESI-MS is complementary to other biophysical methods, such as NMR and analytical ultracentrifugation However, mass spectrometry offers advantages in speed and sensitivity The experimental variables that play a role in the outcome of ESI-MS studies of noncovalently bound complexes are reviewed Several applications of ESI-MS are discussed, including protein interactions with metal ions and nucleic acids and subunit protein structures (quaternary structure)

Studying noncovalent protein complexes by electrospray ionization mass spectrometry

This article describes hybrid materials and systems in which the core integrity of inorganic nanobuilding blocks (NBBs) is preserved and reviews the main synthetic procedures presented in the literature. The relation between the NBB and the resulting hybrid networks is discussed for several striking examples:  silicon and tin oxo clusters, polyoxometalates, and transition metal−oxo-based clusters. This approach is extended to nanoparticule-based hybrids. The chemical strategies offered by the coupling of soft chemistry processes and this approach based on functional NBBs allows, through an intelligent and tuned coding, to develop a new vectorial chemistry that is able to direct the assembly of a large variety of structurally well-defined clusters or nanoparticles into complex architectures.

Designed Hybrid Organic−Inorganic Nanocomposites from Functional Nanobuilding Blocks

Molecular and ionic mimicry and the transport of toxic metals.

Photoprocesses of Copper Complexes That Bind to DNA

Electrospray mass spectrometry applied to inorganic and organometallic chemistry

Synthesis, structure and reactions of [(BuSn)12O14(OH)6]Cl2 · 2H2O: Solution studies using 119Sn NMR and electrospray mass spectrometry

The application of electrospray mass spectrometry to ionic inorganic and organometallic systems

The reactions of manganese carbonyl with the ditertiary phosphorus ligand bis(diphenylphosphino)-methane, dpm, and its arsenic analogue, dam, have been investigated. The major products are of the types Mn2(CO)8(L-L), [(L-L) = dpm or dam], Mn2(CO)6(dpm)2 and Mn2(CO)5(dpm)2.    Mn2(CO)5(dpm)2 displays a carbonyl stretch at the extremely low frequency of 1645 cm-1. It has been shown that the molecule contains a carbonyl group bridging between the manganese atoms in a previously unknown manner.

Derivatives of manganese carbonyl with Bis(diphenylphosphino)methane and Bis(diphenylarsino)methane

Electrospray mass spectra have been obtained from dichloromethane/methanol for cationic species existing in solutions of copper(I)tetrahydroborate derivatives containing phosphine- and phenanthroline-type ligands. Complexes of the type (L-L)Cu(PPh 3 )(BH 4 (L-L=phenanthroline ligand) exist in solution as cationic [(L-L)Cu(PPh 3 )] + species which are easily observed by electrospray mass spectrometry (ESMS).

Copper(I) tetrahydroborate derivatives containing phosphine and phenanthroline ligands : an electrospray mass spectrometric study of species in solution

Ray Colton

Papers

Electrospray mass spectrometry applied to inorganic and organometallic chemistry

Synthesis, structure and reactions of [(BuSn)12O14(OH)6]Cl2 · 2H2O: Solution studies using 119Sn NMR and electrospray mass spectrometry

The application of electrospray mass spectrometry to ionic inorganic and organometallic systems

Derivatives of manganese carbonyl with Bis(diphenylphosphino)methane and Bis(diphenylarsino)methane

Copper(I) tetrahydroborate derivatives containing phosphine and phenanthroline ligands : an electrospray mass spectrometric study of species in solution