Application of a diode‐array detector in capillary electrophoresis

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Abstract
In the last decade diode‐array detection has proved to be extremely useful in high performance liquid chromatography in recording UV‐visible spectra directly and on‐line in the column effluent. In capillary electrophoresis (CE) only fast‐scanning detectors with long scan times (up to 2 s) are commercially available. A home‐made CE instrument with a diode‐array detector (DAD) was built and compared with a commercial fast‐scanning detector. It is shown that the fast‐scanning detector is advantageous when less than eight wavelengths are monitored. Due to the high data collection rate the DAD is superior if high resolution UV‐visible spectra are acquired or if several spectra of a narrow peak (usual peak width in CE below 5 s) are needed for peak purity control. It is shown that DAD detection can help to develop separation methods, to identify peaks according to their UV‐visible spectra, and to check peak purity.