Technical data

20 Agilent 6200 Series TOF and 6500 Series Q-TOF LC/MS System Concepts Guide
1Overview
Electrospray ionization (ESI) and Dual ESI
• Adjust solvent pH according to the polarity of ions desired
and the pH of the sample.
• To enhance ion desorption, use solvents that have low heats
of vaporization and low surface tensions.
• Select solvents that do not neutralize ions through gas-phase
reactions such as proton transfer or ion pair reactions.
• To reduce the buildup of salts in the ion source, select more
volatile buffers.
Multiple charging
Electrospray is especially useful for analyzing large
biomolecules such as proteins, peptides, and oligonucleotides,
but can also analyze smaller molecules like drugs and
environmental contaminants. Large molecules often acquire
more than one charge. Because of this multiple charging, you
can use electrospray to analyze molecules as large as 150,000 u
even though the mass range (or more accurately mass-to-charge
range) for a typical quadrupole LC/MS instrument is around
3000 m/z. For example:
100,000 u / 10 z = 1,000 m/z
The optional Agilent MassHunter
BioConfirm Software performs the
calculations to accomplish
deconvolution.
When a large molecule acquires many charges, a mathematical
process called deconvolution is used to determine the actual
molecular weight of the analyte.