Indirect Detection; Application Of External Pressure - Agilent Technologies 7100 Technical Note

Using the CE in Empower

Indirect detection

The indirect detection mode allows the application of indirect photometric
detection of non-UV absorbing analytes like inorganic cations, inorganic
anions and small carbohydrates.
To attain indirect photometric detection, an ionic compound with a high
UV absorbance intensity is used as the background electrolyte (BGE).
During the separation any non-absorbing analyte causes a reduction of the
high background signal, resulting in negative peaks.
Empower can record and calculate positive and negative signals. If most of
the analytes are non-absorbing, the detector signals for signal and
reference wavelength can be inverted, so that most of the peaks are
positive.

Application of external pressure

For some special applications using high viscosity buffer solution (e.g. a gel
matrix in the CGE and cIEF) the capillary can be conditioned using
external high pressure to ensure that the capillary is filled in adequate
time.
Two additional modes are available for configuration:


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CEC: Capillary Electrochromatography allows high pressure to be
applied on both electrolyte vials in the run during the high-voltage
application to prevent outgassing and bubble formation.
A connected external pressure supply is required for this mode. When
this mode is selected, additional pressure options are available in the
instrument method:
High pressure flush in Preconditioning, Injection and Postconditioning.

External pressure as method setpoint and timetable entry.

CE/p: additional external pressure connected
Agilent 7100 CE in Empower Environment