Diode laser-based detection in liquid chromatography and capillary electrophoresis

Detection techniques involving diode lasers are increasingly of interest in separation science. Diode lasers are small and inexpensive and have a very stable output. However, diode lasers emitting at wavelengths shorter than 635 nm are not commercially available. This seriously limits the applicability of direct detection, since few analytes absorb at such long wavelengths. Because devices that emit at much shorter wavelengths are not expected to become available in the near future, indirect detection schemes involving diode lasers are being developed. These are often based on derivatization with redabsorbing labels and subsequent separation of the label and the various derivatized analytes using either liquid chromatography (LC) or capillary electrophoresis (CE). The application of diode-laser-based detection in CE is of particular interest because the usual detection methods, e.g., absorption detection, do not have the sensitivity required for many applications.