ESI Mass Spectrometer: ESI, APCI, Photodissociation, Positive/Negative Ionization
The mass spectrometer best suited for drug screening using the GPC spin column ESI-MS technique should be the most sensitive with reasonable resolution so that the low levels of compounds can be detected for the weakest binders. Modern Tof mass spectrometers are ideal for screening since they integrate the ion intensities for maximum sensitivity with reasonable resolution. Scanning instruments such as ion traps and quadrupole mass spectrometers have been used as well but are less sensitive and have lower resolving powers. Despite the fact that most reported work has utilized electrospray ionization, since most drug like materials are quite polar, APCI and photodissociation sources can be used as well for less polar materials. Detection in both the positive and negative ionization modes is ideal and automatic switching between modes is possible. However, multiple ionization modes consume more protein and sample throughput is reduced versus a single ionization mode. Most reported work to date has been in the positive electrospray ionization mode.
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