Thomas A. Bellar

Investigation of enhanced ion abundances from a carrier process in high-performance liquid chromatography particle beam mass spectrometry

Enhancements in ion abundances in high-performance liquid chromatography (HPLC) particle beam (PB) mass spectrometry were observed during coelution or when certain substances (e.g., ammonium acetate) were added to the mobile phase during a reverse-phase gradient elution HPLC separation. These enhancements were observed with two commercial PB interfaces and a variety of compounds generally not amenable to separation by gas chromatography. The enhancements are attributed to both improved chromatographic efficiency and a PB carrier process.

Mass transport and calibration in liquid chromatography particle beam mass spectrometry.

Differences in the designs of two liquid chromatography particle beam mass spectrometry systems result in differences in the transport of ammonium acetate and differences in ion abundance-enhancing carrier effects. The effect of mobile phase composition, especially the proportion of water in the mobile phase, on transport efficiency is described. Instrument detection limits for 12 compounds with two different interface designs are presented. The calibrations are generally nonlinear explained in terms of mass transport effects and supported by experiments with isotopically labeled species that coelute with the native species. Summary results of a small multilaboratory study are presented. Calibration with isotopitally labeled internal standards is recommended for real-world environmental samples.

Investigation of the effect of a dc glow discharge on the performance of a particle beam liquid chromatography/mass spectrometry interface

A low voltage (180-V) dc glow discharge device was inserted just below the pneumatic nebulizer in a particle beam interface of a high performance liquid chromatography/mass spectrometry system. The discharge in a helium atmosphere increased the signal produced by 12 test compounds by factors of about 2–6. The increases in signal were probably produced by an increase in the efficiency of solute transmission through the interface. The signal increases caused by the glow discharge were compared to somewhat larger increases caused by 0.01-M ammonium acetate in the mobile phase. The combination of glow discharge and ammonium acetate provided no meaningful advantage over the individual techniques. The mechanism of improved transport efficiency is not proven, but the neutralization of charged particles is a viable hypothesis.