Ion spray is an approach to liquid chromatography/mass spectrometry which includes features common to the electrospray and ion evaporation interfaces. Thermospray is a liquid chromatographic/mass spectrometric technique which utilizes heat and electrolytes in the mobile phase to generate sample ions. In this paper the operation of these two techniques at atmospheric pressure are compared with respect to the effects of solvent composition and electrolyte ion concentration for the production of ions from compounds that are ionized in solution (safranin orange, acid black 1 and testosterone sulfate) and un-ionized in solution (methyl red, adenosine and diethylstilbestrol). The results indicate that at atmospheric pressure ion spray produces ions by the ion evaporation mechanism while thermospray produces ions by both gas-phase chemical ionization and ion evaporation processes.
MATERIALS
Chemicals
The compounds studied are listed in Fig. 1 along with their corresponding structures and relative molecular mass (RMM). Diethylstilbestrol (DES) and adenosine were obtained from Sigma Chemical Co. (St Louis, Missouri, USA). Testosterone sulfate was purchased from Steraloids (Wilton, New Hampshire, USA). Methyl red and safranin orange were generously provided by J. P. Gale and B. L. Bentz of RCA Laboratories (Princeton, New Jersey, USA). Acid black 1 was provided by the US Environmental Protection Agency as part of a project for mass spectrometry of sulfonated azo dyes.'* All other solvents and reagents were high-performance liquid chromatography (HPLC) grade.