Module
UV-VIS detector module
Absorbance detection for GPC/SEC. A selective concentration detector based on a pulsed xenon source.
A UV-VIS absorbance detector for GPC/SEC, based on pulsed xenon technology. It responds to samples that absorb light, and it can be used alongside the other detectors in the array.
Haiku Instruments is developing this module now. Specifications are not published yet.
About the UV-VIS detector
What a UV-VIS detector measures
A UV-VIS detector measures absorbance. Light passes through the flow cell, and the detector records how much of it the sample absorbs. Only molecules with a chromophore absorb in this range, so the detector is selective. That sets it apart from the RI detector, which is universal.
Absorbance is proportional to concentration, so the UV-VIS detector is a concentration detector, like the RI detector. It needs a sample that absorbs light in the 200 to 900 nm range. Whether a given polymer can be seen depends on its chemistry and on the solvent, since many solvents absorb in the ultraviolet as well.
What a pulsed xenon source is
The light source in a UV-VIS detector is usually a lamp that burns continuously, such as a deuterium lamp for the ultraviolet or a tungsten lamp for the visible. A pulsed xenon lamp works differently. It produces short, intense flashes of light instead of a steady beam.
Pulsed xenon lamps are generally described as giving a broad spectrum that reaches from the ultraviolet through the visible. Because the lamp is on only during the flashes, the detector reads the light from each flash rather than from a steady beam.
Where the UV-VIS detector fits among the detectors
The UV-VIS detector is a concentration detector. It can stand in for the RI detector when the sample absorbs, and it can be used with the RI detector when both are available. It does not replace the light scattering detector or the viscometer, which supply molecular weight and structure. The detectors used for each type of calibration are:
- Conventional: RI or UV
- Absolute: RI and light scattering
- Universal: RI or UV, and a viscometer
- Triple: RI, light scattering and a viscometer
- Quad: RI, UV, light scattering and a viscometer