Development of a conductivity-based photothermal absorbance detector for capillary separations

A contactless conductivity-based absorbance detector has been developed for use with capillary separations. Detection is based on a photothermal process. As analytes pass through the detector they absorb light, producing a thermal perturbation. This thermal event results in a change in the solution conductivity. The measured change in conductivity is directly related to the absorption of light. The major advantage to this type of detector is that the measured absorbance is, to a first approximation, independent of optical path length, allowing small-diameter capillaries to be used. This approach combines the optical simplicity of traditional transmission-based instruments with the path length independence of similar refraction-based photothermal detectors. In addition to the initial development and characterization of the photothermal absorbance detector, multiphysical modeling of the heat transfer within the conductivity cell was performed.