Electrospray Ionization - Variants

Variants

The electrosprays operated at low flow rates generate much smaller initial droplets, which ensure improved ionization efficiency. In 1994, two research groups coined the name micro-electrospray (microspray) for electrosprays working at low flow rates. Emmett and Caprioli demonstrated improved performance for HPLC-MS analyses when the electrospray was operated at 300–800 nL/min. Wilm and Mann demonstrated that a capillary flow of ~ 25 nL/min can sustain an electrospray at the tip of emitters fabricated by pulling glass capillaries to a few micrometers. The latter was renamed nano-electrospray (nanospray) in 1996. Currently the name nanospray is also in use for electrosprays fed by pumps at low flow rates, not only for self-fed electrosprays. Although there may not be a well-defined flow rate range for electrospray, microspray, and nano-electrospray, studied "changes in analyte partition during droplet fission prior to ion release" . In this paper, they compare results obtained by three other groups. and then measure the signal intensity ratio / at different flow rates.

Cold spray ionization is a form of electrospray in which the solution containing the sample is forced through a small cold capillary (10-80 °C) into an electric field to create a fine mist of cold charged droplets. Applications of this method include the analysis of fragile molecules and guest-host interactions that cannot be studied using regular electrospray ionization.