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Software by NIST for compression of structure with mass spectra. The program seeks to find mechanisms and their rates for all fragmentation types (EI, Tandem positive and negative mode) and correlates mass spectral peaks to a probable origin structure. It contains an isotope calculator and other features and on-line help.
In positive ion mode, DART produces predominantly protonated molecules [M+H] + and in negative-ion mode deprotonated molecules [M-H] −. Both negative and positive modes of DART provides relatively simple mass spectra. Depending on the type of analyte, other species may be formed, such as multiple charged adducts. DART is categorized as a soft ...
The mass range is the range of m/z amenable to analysis by a given analyzer. The linear dynamic range is the range over which ion signal is linear with analyte concentration. Speed refers to the time frame of the experiment and ultimately is used to determine the number of spectra per unit time that can be generated.
When a surface is immersed in a solution containing electrolytes, it develops a net surface charge.This is often because of ionic adsorption. Aqueous solutions universally contain positive and negative ions (cations and anions, respectively), which interact with partial charges on the surface, adsorbing to and thus ionizing the surface and creating a net surface charge. [9]
The total number of cations (positive ions) should be equal to the total number of anions (negative ions), so that the overall electrical charge is neutral. However, routine tests do not measure all types of ions. The anion gap is representative of how many ions are not accounted for by the lab measurements used in the calculation. These ...
The above table simplifies the dopant process. In fact, there may be extensive ion-molecule chemistry between dopant and solvent before the analyte becomes ionized. APPI can also produce negative ions by creating a high abundance of thermal electrons from dopant or solvent ionization or by photons striking metal surfaces in the ionization source.
In the negative mode, [M−H] − ions are produced by either proton abstraction, or [M+X] − ions are produced by anion attachment. Most work on the APCI-MS analysis has been in positive mode. In the positive mode, when the discharge current of corona discharge is 1-5 μA on the nebulized solvent, N 2 gas molecules are excited and ionized ...
The greater the positive charge placed on the gate, the more positive the applied gate voltage, and the more holes that leave the semiconductor surface, enlarging the depletion region. (In this device there is a limit to how wide the depletion width may become.