Liquid Chromatography Detectors - The Fluorescence Detector > The Single Wavelength Excitation Fluorescence Detector > Page 57

The Single Wavelength Excitation Fluorescence Detector

The single wavelength excitation fluorescence detector is probably the most sensitive LC detector that is available, but is achieved by forfeiting versatility. A diagram of a simple form of the fluorescence detector is shown in figure 36.

The excitation light is normally provided by a low pressure mercury lamp which is comparatively inexpensive and provides relatively high intensity UV light at 253.7 nm. Many substances that fluoresce will be excited by light of this wavelength.



Figure 36. The Single Wavelength Excitation Fluorescent Detector

The excitation light is focused by a quartz lens through the cell. A second lens, set normal to the incident light, focuses the fluorescent light onto a photo cell. A fixed wavelength fluorescence detector will have a sensitivity (minimum detectable concentration at an excitation wavelength of 254 nm) of about 1 x 10-9 g/ml and a linear dynamic range of about 500 with a response index of 0.96 < r <1.04.