Different Types of Lamps in UV-Vis Spectrophotometer


An ultraviolet-visible spectrophotometer can measure the wavelength of light near UV and near Infrared range i.e. from 190 nm to 1100 nm. It is used in the quantitative determination of concentrations of the absorber in the solutions of transition metal ions and highly conjugated organic compounds.

The UV/VIS spectrophotometer has a different specific sample cell (sample chamber), and cuvette (sample tube) and also have different types of light sources. The different light sources that are used in spectrophotometer are deuterium light source, halogen light source, deuterium-halogen light source, xenon light source, tungsten light source. Today the spectrophotometer comes with different light sources that change its wavelength automatically for optimized and interruption-free operation.

The choice of a light source in the spectrophotometer depends on various factors. The desirable features for light sources are:

•    Uniform light output over a specified wavelength range

•    Stability of response over extended time periods

•    Long usage lifespan

•    Low cost

Various light sources used in UV/VIS spectrophotometer are described below:

Deuterium Light Source

Deuterium Lamps are the most common light sources for the UV region (160-375nm). The lifespan of the typical deuterium lamp is around 1000 hours. The gas envelope and windows in the lamp are made of quartz. These lamps are superior over other lamps but it is necessary to warm-up the lamp to the sufficient time and stable power supply for maintaining a constant temperature and current during operation.

Deuterium-HalogenLight Source

The deuterium-halogen light source is an integrated composite light source for the UV-VIS-IR wavelength (190-2500 nm). Thus it covers the entire UV and visible light wavelength. It has an integrated shutter that opens and closes using a switch or external light path. The light source has stable power output due to the high-quality bulb, stable current control, and efficient heat dissipation because of the presence of fan and heat sink.

Tungsten-Halogen Light Source

Halogen lamps are also known as tungsten or quartz lamp. The wavelength range of halogen lamps lies in the visible region (320 nm to 1100 nm). The lifespan of a halogen lamp is 2000 hours.

Tungsten lamp alone can measure the light in the wavelength of 350-2200 nm. The constant voltage should be employed while operating a lamp to get a stable response.

Tungsten-halogen lamps consist of quartz envelope filled with inert gas and halogen (iodine). Iodine and tungsten from tungsten iodide, that is volatile in nature. Tungsten-halogen lamps bring the output closer to the UV region (240-2500 nm) and it also extends the lamp life to almost double of a normal tungsten lamp.

Xenon Light Sources

Xenon source covers the entire range of UV-visible and even beyond (160-2000 nm). They are less stable than deuterium lamps. Pulsed Xenon lamps are beneficial as they generate less heat, have a longer life due to the slow decay of sample.

Mercury-Xenon Light Sources

It uses a mixture of mercury vapours and xenon gas. Such lamps emit broad spectrum and include sharp peaks in both UV and visible region. The lamp has high utility over xenon lamps due to high output intensity, stability, and longer useful life. 

Make a judicious choice of the lamp on the basis of the wavelength range, intensity requirement, stability, and lifespan of the lamp.



Location: Australia

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