What Is a Fluorometer?

Ray Hawk

A fluorometer is a special type of optical device usually used in laboratory settings, which is capable of measuring the fluorescent quality of biological or mineral samples. Fluorescence occurs when a substance emits visible light and appears to glow after it has been exposed to some type of radiation, whether visible light itself or high-energy radiation such as from x-rays. This property is similar to phosphorescence, which is a low-temperature light emission of a build up of energy or radiation from a substance. The fluorometer can be either a handheld device or a tabletop unit, and its sensitivity can be tuned to specific wavelengths of light using filters and depending on what is being studied.

Scientist with beakers
Scientist with beakers

The design of any typical fluorometer has several key components. It has an input source for ordinary visible light, and this light is passed through an excitation filter that allows only specific wavelengths of it to impact onto a sample cell of the material being studied. When this material, whether organic or inorganic, is bombarded by these controlled wavelengths of light, it fluoresces, emitting characteristic light of its own that is then passed through an emission filter. The emissions are read by a light detector which produces a readout for the observer to know how the sample is reacting and what its contents are.

Though fluorometer detection is based on fundamental universal principles for fluorescence, there are several unique applications and adaptations for the devices. One of the main uses is as a chlorophyll fluorometer, which is calibrated to measure the ambient fluorescent quality of plants. Plants do not absorb all of the light that they receive from the sun, and reflect some of this back out into the surrounding environment through the green chlorophyll pigment contained in their cell structures. Measuring this fluorescence can be useful in determining the health of plants, and is instrumental in agricultural and botany research.

Handheld fluorometer devices are also common to medicine and biological research. Liquid samples can be given trace bacterial enzymes that cause chemical reactions and fluorescence in the solution, for detecting the presence of other bacteria at the initial reproductive colony level in a matter of minutes. The same devices can be used to detect fluorescent inorganic molecules such as lead down to as little as one part per trillion. Some doctors recommend using them to detect similar minerals such as zinc protoporphyrin (ZPP), which can indicate an iron deficiency in patients. Fluorometer detection is also common to geological research, such as in analyzing samples to determine if uranium deposits are in high enough concentrations for mining operations to take place.

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