What is the Difference Between Spectrophotometer and Spectrofluorometer

The key difference between spectrophotometer and spectrofluorometer is that spectrophotometer involves the measurement of absorption, whereas spectrofluorometer involves the transition of polyatomic fluorescent molecules from their higher energy level to a ground state by lowering their energy level through emission of photons.

A spectrophotometer is an analytical instrument that can measure the concentration of a sample by measuring light absorption. Spectrofluorometer is an analytical instrument in which fluorescent properties of some compounds are used in order to get information about the concentration and the chemical properties of the sample.

CONTENTS

1. Overview and Key Difference
2. What is a Spectrophotometer
3. What is a Spectrofluorometer 
4. Spectrophotometer vs Spectrofluorometer in Tabular Form
5. Summary – Spectrophotometer vs Spectrofluorometer 

What is a Spectrophotometer?

A spectrophotometer is an analytical instrument that can measure the concentration of a sample by measuring light absorption. It uses the reflection or transmission properties of a material as a function of wavelength. This instrument can operate at visible light, near UV, and near IR lights, as well. We use a cuvette to place the sample inside the instrument. Then a light beam passes through the sample and diffracts into a spectrum of wavelengths. Then the instrument measures the intensities via a charge-coupled device. Finally, we get the results of the analysis on the display device after passing the detector.

We can use this instrument to detect organic compounds as well. That is by determining the absorption maxima. Moreover, we can use it to determine the colour within a spectral range. Most importantly, we use it to measure the concentration of a component in a sample by determining the amount of light absorbed by that component.

What is Spectrofluorometer?

Spectrofluorometer is an analytical instrument in which fluorescent properties of some compounds are used in order to get information about the concentration and the chemical properties of the sample. In this instrument, we need to select a certain excitation wavelength. We can observe the emission at a single wavelength, or we can just scan the sample in order to record the intensity against the wavelength. This is also called an emission spectrum. We can use this instrument in fluorescence spectroscopy.

Typically, this instrument uses a high-intensity light source for the bombardment of a sample with a large number of photons. Therefore, it allows a maximum number of molecules to obtain an excited state at a certain point at a given time. In this process, the light may pass through a filter at a selected fixed wavelength. Or else, light can pass through a monochromator that can allow a wavelength to be selected, allowing it to be used the exciting light. In this instrument, the emission is collected in a direction that is perpendicular to the emitted light. Moreover, the emission can be passed through a filter or a monochromator before it is detected by a photomultiplier tube, photodiode, or charge-coupled device detector. Further, the signal is given as either a digital output or as an analog output.

There are many other options available in this instrument: polarizers, cryostats, cold finger dewars, LEDs for lifetimes, filter holders, manual slits, filter wheels, computer-controlled slits, integrating spheres, etc.

What is the Difference Between Spectrophotometer and Spectrofluorometer?

Spectrophotometer and spectrofluorometer are important analytical instruments. The key difference between spectrophotometer and spectrofluorometer is that spectrophotometer involves the measurement of absorption whereas spectrofluorometer involves the transition of polyatomic fluorescent molecules from their higher energy level to a ground state by lowering their energy level through emission of photons.

The below infographic presents the differences between spectrophotometer and spectrofluorometer in tabular form for side by side comparison.

Summary – Spectrophotometer vs Spectrofluorometer

Spectrophotometer and spectrofluorometer are important analytical instruments. The key difference between spectrophotometer and spectrofluorometer is that spectrophotometer involves the measurement of absorption, whereas spectrofluorometer involves the transition of polyatomic fluorescent molecules from their higher energy level to a ground state by lowering their energy level through emission of photons.

Reference:

1. “Fluorescence-Spectrophotometer.” Labcompare.

Image Courtesy:

1. “Spectrophotometer Model 1” By Viv Rolfe – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Schematic-diagram-of-the-arrangement-of-optical-components-in-a-typical Spectrofluorometer” By IOP Publishing Ltd – Changzheng Li and Yanan Yue, "Fluorescence spectroscopy of graphene quantum dots: temperature effect at different excitation wavelengths, IOP Publishing Ltd, Nanotechnology, Volume 25, Number 43 , 2014 (CC BY-SA 3.0) via Commons Wikimedia