1. Application and optimization of thermospray HPLC/MS with direct electrical heating of the capillary vaporizer. 2. A moving belt transport detector for HPLC based on thermospray vaporization

This dissertation is composed of two parts. In Part 1, the new version of thermospray high performance liquid chromatography/mass spectrometry (HPLC/MS) with direct electrical heating of the capillary vaporizer is described and applied to real on-line HPLC/MS analyses. The effect of fundamental parameters, such as vaporizer temperature, jet temperature, solvent composition, mobile phase flow rate, and electrolyte concentration are reported. Effects of these parameters on thermospray performances are discussed as well as the thermospray ionization mechanism. A new technique for calibration of the mass axis under thermospray operating conditions is described. The results show that polyglycols make excellent calibration standards. The thermospray HPLC/MS analysis of a drug mixture under reversed phase gradient elution conditions is reported. Reproducible spectra from each component of the sample eluted from the HPLC column are obtained with molecular ion species as base peaks in all cases. Detection limits are determined as 10 nanograms or less in the full scan mode. Comparison of chromatograms detected by on-line UV absorption and by mass spectrometry shows that chromatographic fidelity is preserved in the thermospray interface. A profile of a biological fluid, water soluble metabolites extracted from guinea pig urine, is obtained with the thermospray HPLC/MS. One of the styrene oxide metabolites, a methylsulfonium ion, is tentatively identified by comparison with synthetic compounds. In Part 2, a moving belt transport detector for HPLC is described which employs thermospray deposition of the sample onto a moving stainless steel belt with subsequent vaporization or pyrolysis into a flowing gas stream for detection in a conventional GC detector. This detector is superficially similar to earlier transport devices in that a moving surface is required and the sample is detected after the solvent is removed. The major unique feature of the new approach is that the solvent is vaporized and removed without being deposited as liquid on the moving surface. The performance of this new transport detector is evaluated by coupling it to a photoionization detector (PID), using amino acids and peptides as test samples. Thermospray deposition efficiency is as high as 69% for phenylalanine in aqueous solution. Detection limits of this thermospray transport PID are typical in the 10-400 pmol range. The system performs satisfactorily with both aqueous and nonaqueous solvents at flow rates typical for HPLC. Performance of the thermospray transport system with electron capture detector (ECD) is also reported using chlorinated pesticides as test samples.