Thermo Scientific HESI-II Probe, User Manual

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1
Introduction
4 HESI-II Probe User Guide Thermo Scientific
Organic solvents, such as methanol, acetonitrile, and isopropyl alcohol, are superior to water
for H-ESI. Volatile acids and bases are good, but salts above 10 mM concentration and strong
acids and bases are extremely detrimental.
Follow these rules for achieving a good electrospray:
• Keep salts out of the solvent system.
• Use organic/aqueous solvent systems and volatile acids and bases.
• Optimize the pH of the solvent system.
Table 1 shows initial heated electrospray settings for different liquid flow rates for a 50 percent
aqueous solution. These initial settings provide a starting point for optimizing system
performance. The optimal settings for your application depend on the compounds of interest,
the solvent matrix, and the chromatographic conditions. For information on optimizing these
settings, refer to the getting started guide for your mass spectrometer.
For an LTQ Series mass spectrometer, the allowable range for the auxiliary gas flow depends
on the version of the instrument control software and the vaporizer temperature setting:
• For LTQ 2.5.0 or lower, the allowable range for the auxiliary gas flow is 5 to 60 units.
• For LTQ 2.5.5 or higher, the allowable range for the auxiliary gas flow is 0 to 60 units for
vaporizer temperatures up to 100.00 °C. For vaporizer temperatures above 100.00 °C, the
minimum auxiliary gas flow is 5 units.
For a TSQ Series mass spectrometer, you can set the auxiliary gas flow from 0 to 60 units.
Tip For best results, avoid operating the HESI-II probe at elevated temperatures without
solvent flow from the LC system or the syringe pump. Allowing the HESI-II probe to run
dry at elevated temperatures can cause blockage of the replaceable metal needle (see
“Replacing the Needle Insert” on page 20 ).
Tip For best results, set the auxiliary gas flow to a minimum of 5 units for vaporizer
temperatures above 100.00 °C.
Table 1. Initial heated electrospray settings
Liquid
flow rate
(μL/min)
Ion transfer
tube
temperature
(°C) H-ESI
vaporizer
temperature
(°C)
Sheath gas
pressure
(psi) Auxiliary gas
flow
(arbitrary units)
Spray voltage
(V)
Typical
nitrogen gas
consumption
(L/min)
5 240 Off to 50 5 0 +3000 (-2500)
*
<1
200 350 250 to 350 35 10 +3000 (-2500
)
8
500 380 300 to 500 60 20 +3000 (-2500
)
13
1000 400 500 75 20 +3000 (-2500
)
17
*
Negative ion mode