Introduction; Chapter 1 Introduction - Thermo Scientific HESI-II Probe User Manual

1

Introduction

Heated-electrospray ionization (H-ESI) transforms ions in solution into ions in the gas phase
by using electrospray ionization (ESI) in combination with heated auxiliary gas. You can use
H-ESI to analyze any polar compound that makes a preformed ion in solution.
+
Basic compounds (for example amines) can form a protonated molecule [M + H] , and acidic
-
compounds (for example sulphonic acids) can form a deprotonated molecule [M – H] . In the
positive ion polarity mode, the protonated molecule produces a peak at an m/z value of
M + 1, where M equals the mass of the original molecule. In the negative ion polarity mode,
the deprotonated molecule produces a peak at an m/z value of M – 1, where M equals the
mass of the original molecule.
Because solution chemistry is the primary factor affecting mass spectra in ESI, other common
+ + +
adducts include sodium ions (Na ), yielding an m/z value of [M + 23] ; potassium ions (K ),
+ +
yielding an m/z value of [M + 39] ; and ammonium ions (NH ), yielding an m/z value of
4
+
[M + 18] .
This chapter describes the principles of the heated-electrospray ionization technique through
use of the HESI-II probe (see Figure 1) and a Thermo Scientific mass spectrometer.
Figure 1. HESI-II probe
Thermo Scientific HESI-II Probe User Guide 1