Light Pipe
Definition and meaning of Light Pipe in chemistry.
A light pipe is an optical device used to guide and transmit electromagnetic radiation from a source to a detector or reaction vessel with minimal loss of intensity.
In more detail
In analytical chemistry, light pipes are commonly used in instrumentation such as Fourier transform infrared (FTIR) spectroscopy, particularly when interfacing gas chromatography with FTIR (GC-FTIR). They rely on internal reflection to keep the light beam focused along the length of the tube, even if the pipe is curved or bent. The interior surface of the pipe is highly polished or coated with highly reflective materials like gold to maximize transmission efficiency of the infrared beam. Minimizing the volume of the light pipe is also critical to prevent broadening of the chromatographic peaks.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Internal Coating | Gold or silver |
| Application | GC-FTIR interfaces |
In a GC-FTIR system, a gold-coated light pipe acts as the gas flow cell where the gaseous effluent from the chromatograph is irradiated by the infrared beam to collect absorption spectra.
Frequently asked questions
Why is gold used to coat light pipes in FTIR?
Gold provides excellent reflectivity for infrared radiation and is chemically inert to most GC effluents.
Can optical fibers act as light pipes?
Yes, fiber optics are a type of solid light pipe that use total internal reflection to guide ultraviolet, visible, or near-infrared light.