Mass of an ion or molecule calculated using the mass of the most abundant isotope of each element rounded to the nearest integer value and equivalent to the sum of the mass numbers of all constituent atoms

An atomic or molecular species having a net positive or negative electric charge

An ion formed with an internal energy higher than the dissociation threshold but with a sufficient lifetime that it can exit the source and enter the mass spectrometer where it dissociates

One of several forms of an element having the same atomic number but differing atomic masses

The most intense peak in the spectrum

The sum of all the separate ion currents contributing to the spectrum

The current of a specified m/z ion current

In a mass spectrum, the observed mass divided by the difference between two masses that can be separated: m/Am. The procedure by which Am was obtained and the mass at which the measurement was made should be reported.

Means that a mass spectrometer is able to differentiate two peaks (generally the isotopes) distant of 1 m/z unit

Smallest mass difference (Am) between two equal magnitude peaks so that the valley between them is a specified fraction of the peak height

An ion containing no unpaired electrons in its ground electronic state

An ion containing unpaired electrons in its ground state Electron impact ionization Positive chemical ionization Negative chemical ionization

Atmospheric pressure ionization: generic term for ionization techniques occurring at atmospheric pressure

Electrospray ionization: most commercial systems operate with pneumatically assisted electrospray (originally defined as ion spray)

Table 1.6 (continued) Nano-ESI

APCI APPI MALDI Mass analyzer

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