Mass spectrometer-target collection

Vapor pressures of phases in these systems were measured by the Knudsen effusion technique. Use of mass spectrometer-target collection apparatus to perform thermodynamic studies is discussed. The prominent sublimation reactions for these phases below 2000 K was shown to involve formation of elemental plutonium vapor. Thermodynamic properties determined in this study were correlated with corresponding values obtained from theoretical predictions and from previous measurements on analogous intermetallics. 

Equilibrium vapor pressures were measured in this study by means of a mass spectrometer/target collection apparatus. Analysis of the temperature dependence of the pressure of each intermetallic yielded heats and entropies of sublimation. Combination of these measured values with corresponding parameters for sublimation of elemental Pu enabled calculation of thermodynamic properties of formation of each condensed phase. Previ ly reported results on the subornation of the PuRu phase and the Pu-Pt and Pu-Ru systems are correlated with current research on the PuOs and Pulr compounds. Thermodynamic properties determined for these Pu-intermetallics are compared to analogous parameters of other actinide compounds in order to establish bonding trends and to test theoretical predictions. 

Vapor pressures were determined by using the Knudsen effusion technique. Effusion rates through and orifice contained in each sample cell were measured as a function of temperature by use of a mass spectrometer/target collection... 

Mass spectrometer-target collection technique, measurement of... 

Measurement of the very low pressures associated with many of the Pu-intermetallics requires the high sensitivity afforded by target collection. To identify the gas phase species which are in the effusates, a mass spectrometer is needed. The excellent agreement between the mass spectrometric and target collection results confirms the predominance of the Pu gaseous species in the sublimation of these intermetallics. 

Target collection technique, mass spectrometer, and measurement... 

Another interface commonly used for connecting HPLC to a mass spectrometer is not a true in-line interface. It is a robotically controlled spotter plate system for collecting samples from the HPLC to be injected into the MALDI time-of-flight laser ionization mass spectrometer for analyzing proteins and large peptides. The effluent sample dropped in the plate well is mixed with an ionization matrix already present, solvent and volatile reagents are evaporated, and the plate is then placed into the injector target and blasted with a pulsed laser to volatilize and ionize sample into the atmosphere of the interface where it can be drawn into the mass spectrometer. 

To make sure the target is clean, we spot matrix onto the target and then collect data in the mass spectrometer to see whether any sample contamination appears. 

The headspace method, less sensitive compared to the P T method, in which the sample is placed in a sealed container, such as a vial, and left at a constant temperature until the gas and liquid phases are in equilibrium. The target substances in the gas phase (headspace) are collected by gas tight syringe, and injected into the gas chromatograph-mass spectrometer. 

Mass spectrometer is a powerful tool for the identification of analytes however, a direct free connection between liquid chromatography and mass spectrometry is not permitted. At the very least, inorganic salts should be ehmi-nated before the use of a mass spectrometer. One approach is to collect the target fraction in a small trapped column, and then wash off the unwanted components before introduction to the mass spectrometer. Even if one uses a small column with a volatile salt, one must wash the mass chamber very often to maintain its sensitivity. 

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