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Optimization protocol 6-9
Ultrasound plus vacuum
Ultrasonic agitation combined with vacuum degasses solvent very quickly.
This technique is less likely to change the composition of mixed solvents than
vacuum alone because the mixed solvents are held under vacuum for only a
short time (less than a minute is usually sufficient).
Optimization protocol
You must select the appropriate application operating parameters to obtain
the best performance from your detector. Nebulizer gas flow rate, nebulizer
temperature, and drift tube temperature must all be optimized for the best
results.
Nebulizer gas pressure
Increased nebulizer gas flow rate causes a decreased signal response because
of the resulting formation of smaller droplets that scatter less light. Lower gas
flow rates tend to be more favorable because less gas is consumed and a better
sensitivity is achieved. However, at some point this benefit is offset by an
increase in baseline noise from the inefficient nebulization of the eluent,
resulting in large droplets. The particle size of these droplets results in
complex scattering mechanisms and poor detector performance. If you reduce
the eluent flow, you must also reduce the nebulizer gas flow rate to maintain
the optimum nebulized droplet size. Never decrease the nitrogen flow rate
below 170 kPa (1.7 bar, 25 psi).
Nebulizer temperature
Note:
Setting the nebulizer temperature high enough to boil the solvent can
cause excessive baseline noise.
The detector starts more quickly when you decrease the temperature of the
nebulizer chamber. The cooling option was added to effect faster equilibration.
Warning:
Do not apply vacuum to the brown glass bottles in which
solvent is shipped. There is a high risk of implosion under these
conditions. Use a thick-walled container designed for vacuum
applications.