|Inorganic Mass Spectrometry|
The ability to measure trace and ultra- trace levels of elements in environmental and biomedical samples is critical with the present need for mechanistic studies in environmental remediation and therapeutic drug metabolism research. Inductively coupled plasma mass spectrometry (ICP/MS) is a forefront technique for measuring elements at the part-per-billion to part-per-trillion levels (equivalent to 1 needle in 106 haystacks!). In this research we are trying to develop a mechanistic understanding of the interactions of very small particles (< 20 nm) with high temperature (6,000-10,000 K) argon plasmas and thereby attempting to develop more accurate and more versatile measurements.
Liquid Chromatography/Mass Spectrometry
Our research group has developed a new aerosol-based interface for liquid chromatography/mass spectrometry, the Particle Beam Interface (PB-LC/MS). This patented device has been developed commercially and over four hundred instruments are currently in use in university, government and industrial laboratories worldwide. Our current research aims to gain a better understanding of the mechanisms of aerosol formation, solvent evaporation, particle transport and particle vaporization in the interface, in order to improve linearity and detection limits. We are also studying laser desorption (cw Ar ion and pulsed CO2) ionization techniques for on- line PB-LC/MS.
Inductively Coupled RF Plasma (ICPAES) and Microwave Plasma (u-AES) Atomic Emission Spectrometry
We have for a number of years developed techniques for sample introduction into various plasmas for atomic emission spectrometry. We are especially interested in the ability to use these plasmas as detectors for liquid chromatography, in order to provide speciation information (i.e. identifying the metal by its organic ligand) on the nature of many organometallic compounds, both naturally occurring and synthetic. Present work includes studies with a low pressure (10 torr) microwave plasma as an LC atomic emission detector.
Aerosols form a major part of much of our research efforts. They are used as intermediaries between the condensed phase of sample solutions and the vapor phase of measured atoms and ions, both at atmospheric pressure (ICPAES) and at reduced pressure (ICP/MS and PB- LC/MS). We are presently studying mechanisms of aerosol formation processes and also collisional and gas dynamic processes which follow formation. Techniques used for characterizing aerosols in the 100 nm to 50 um size range include laser Fraunhofer scattering and Scanning Electron Microscopy for particle sizing, and laser Doppler velocimetry for directional particle velocity measurements, up to sonic velocities.