being the most common. DADs are increasingly preferred because of their
ability to monitor at multiple selected wavelengths and the complete spectral
information provided. The detector cell is normally a portion of the capillary
itself, sometimes enlarged (bubble cell) or bent so as to increase the optical path
and hence the sensitivity. Table 3summarizes the characteristics of the more
important detectors.Table 3. Characteristics of CE and CEC detectors.
Detector Sensitivity Sensitivity Characteristics
mass (moles) concentration
(molar)
UV-visible absorbance 10 -^13 –10-^1610 -^5 –10-^8 Good sensitivity, most widely
used. DADs are versatile and
give spectral information.
Fluorescence 10 -^15 –10-^1710 -^7 –10-^9 Sensitive, but many solutes
need to be derivatized.
Laser-induced fluorescence 10-^18 –10-^2010 -^14 –10-^16 Extremely sensitive, but many
solutes need to be
derivatized. Expensive.
Electrochemical Sensitive, require special
Amperometric 10 -^18 –10-^1910 -^10 –10-^11 electronics and capillary
Conductometric 10 -^15 –10-^1610 -^7 –10-^8 modification. Conductometric
almost universal.These aspects of CE and CEC closely parallel those described for GC and HPLC
(Topics D4 and D6). Additional instrument parameters to be set and monitored
or controlled include:● applied potential and run-time;
● temperature (heat dissipation);
● hydrodynamic and electrokinetic sample-injection.Instrument
control and data
processing
D8 – Electrophoresis and electrochromatography 181