Upon separation by LC, the components can be detected using optical properties such as ultraviolet-visible (UV-VIS), fluorescence, refractive index, evaporative light scattering or electrical conductivity based on the analytes' properties. Figure 2 shows the various detectors for LC. When the analyte passed through the detector, a change (e.g. increase or decrease) in the optical property will be observed and recorded.
Chromatograms obtained using these optical detectors primarily identify or qualify substances based on the retention time and quantitate substances based on the peak area and intensity. The LC chromatogram (Figure 3, in red) shows an example of a typical chromatogram obtained using these optical detectors. LC coupled with optical detection offers great quantitative accuracy for analytes that can be chromatographically resolved, where a detected peak comprises only a single component. However, achieving required resolution is challenging for complex samples where multiple components elute approximately at the same time.