The utility of field desorption mass spectrometry for quantitative metal cation analysis in forensic sciences is demonstrated by the determination of a lethal thallium level in the brain tissue of an experimental animal. Stable isotope dilution and accumulation of the electrically recorded field desorption ion currents with a multi-channel analyzer allowed a direct estimation of thallium in homogenized tissue samples without further pretreatment. Experiments with standard solutions revealed the limit of detection for thallium to be about 10pg of the metal cation.
Quantitative ultratrace analysis (10 nmol to 10 /cmol/1) of cesium in biological samples such as human body fluids and animal tissues is performed without any prior purification or concentration steps. The normal level of cesium ions in heart cells was determined. After poisoning these cells with high concentrations of the alkali cation much higher levels were found inside the cells then had been suggested previously. It is demonstrated that field desorption mass spectrometry is a unique tool for the qualitative and quantitative investigations of metal cations in biological material.
Field Desorption Mass Spectrometry, a-Amino Acid Methionine The fragmentation of methionine in field desorption mass spectrometry has been studied. Decomposition mechanisms are described which are based on stable isotope labelling, low and high resolution field desorption, and the application of field desorption kinetics. The combined use of these techniques for the study of some fundamental fragmentations in field desorption is demonstrated successfully. Further, a comparison with the fragmentation pattern of methionine under electron impact, chemical ionization and Curie point pyrolysis is given.