Capability, dissolving ionization

The objective of the preceding discussion of CdS electrodes has been to point out the possible role of two types of identifiable surface states one a state intrinsic to the CdS surface, presumably associated with Cd, which is eventually ionized by reaction with a hole and dissolved into solution the other is a sulfide ion deposited on the CdS surface from solution. By considering these as surface states capable of inelastic... 

Multi-element determination of dissolved metals at ultratrace level may be performed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). U.S. EPA s Methods 200.8 and 1638 present a methodology for measuring trace elements in waters and wastes by the above technique. Sample is acid digested and the solution is introduced by pneumatic nebulization into a radio-frequency plasma. The elements in the compounds are atomized and ionized. The ions are extracted from the plasma through a differentially pumped vacuum interface and separated by a quadrupole mass spectrometer by their mass to charge ratios. The mass spectrometer must have a resolution capability of 1 amu peak width at 5% peak height. 

The only gases that dissolve appreciably in water are those that are capable of hydrogen bonding (such as HF), those that ionize (such as HCl, HBr, and HI), and those that react with water (such as CO2). 

In 1981, Barber and co-workers at the University of Manchester Institute of Science and Technology introduced fast atom bombardment (FAB), which produced a continuous source of ions from nonvolatile molecules dissolved in a liquid matrix. Such sources were easily retrofitted to existing sector and quadrupole mass spectrometers, and they profoundly improved capabilities for the structural analysis of peptides, carbohydrates, and other biological molecules. In addition, a continuous flow FAB interface was later introduced that enabled online interfacing with hi ih-performance liquid chromatography (HPLC). Thus, this powerful, new ionization technique continued to reinforce the preeminence of sector and quadrupole mass spectrometers, and did little to advance either the technology or the popularity of time-of-flight instruments. 

Pioneering laser desorption (LD) capabilities (Posthumus et al. 1978) have been greatly extended (Karas and Hillenkamp 1988) by dissolving the sample in a solid matrix that is a highly efficient absorber of the laser radiation, so as to ionize molecules as large as 300 kDa (Hillenkamp et al. 1991). The absence of matrix effects and mass measuring errors of 0.01%-0.1% make LD a particularly promising method for protein mixtures (Chait et al. 1990). 

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