Difference Between Flame Photometer and Spectrophotometer

The key difference between flame photometer and spectrophotometer is that the flame photometer uses a controlled flame test whereas the spectrophotometer uses the absorption of light by the components in a sample.

Both the flame photometer and spectrophotometer are analytical instruments that we use to analyze inorganic samples. Both these techniques can measure the concentrations of desired components in a given sample.

CONTENTS

1. Overview and Key Difference
2. What is Flame Photometer
3. What is Spectrophotometer
4. Side by Side Comparison – Flame Photometer vs Spectrophotometer in Tabular Form
5. Summary

What is Flame Photometer?

Flame photometer is an analytical instrument in which we use a controlled flame test. There, we use the intensity of a flame in order to determine the concentration of the metal present in a sample. Thus, we can quantify the intensity of the flame colour using photoelectric circuitry. This intensity depends on the amount of energy absorbed by the atoms in producing a flame via vaporizing them.

More importantly, we should introduce the sample to the flame at a constant rate. There are filters that can select the flame colour. These filters can exclude the interferences coming from other atoms or ions. However, we need to calibrate the instrument before using it. For this calibration, we can use a series of standard solutions of the ion that we are going to test. Moreover, the major chemical elements that we can easily quantify using this instrument include sodium, potassium, lithium and calcium. Most of the times, group 1 and group 2 elements are very sensitive to this test since they have low excitation energies.

Parts of a flame photometer:

• Source of flame – A burner that produces the flame.
• Nebulizer and mixing chamber – Transports the sample to the flame at a constant rate.
• Optical system – Act as the filter.
• Photo detector – Detects the emitted light and quantify the intensity of the flame colour.

What is Spectrophotometer?

A spectrophotometer is an analytical instrument that can measure the concentration of a sample via measuring the 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 and 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 the Difference Between Flame Photometer and Spectrophotometer?

The flame photometer is an analytical instrument in which we use a controlled flame test. There we use a controlled flame test and measures the intensity of a flame produces by a sample and quantifies that intensity. Spectrophotometer, on the other hand, is an analytical instrument which can measure the concentration of a sample via measuring the light absorption. That is, this technique uses the absorption of light by the components in a sample. This is the key difference between flame photometer and spectrophotometer. Moreover, flame photometer works at the visible range of wavelengths while the spectrophotometer works at visible light, near UV, and near IR light range as well.

The below infographic presents a detailed comparison of the difference between flame photometer and spectrophotometer in tabular form.

Summary – Flame Photometer vs Spectrophotometer

Both flame photometer and spectrophotometer are analytical instruments that we use to measure the concentration of components in samples via optical techniques. The main difference between flame photometer and spectrophotometer is that the flame photometer uses a controlled flame test whereas the spectrophotometer uses the absorption of light by the components in a sample.

Reference:

1. “Photoelectric Flame Photometer.” Wikipedia, Wikimedia Foundation, 10 Apr. 2018. Available here  
2. AMASM Follow. “Spectrophotometer.” LinkedIn SlideShare, 15 Apr. 2009. Available here

Image Courtesy:

1.”Auto Flapho FP8800″ By A.KRÜSS Optronic (CC BY-SA 3.0 de) via Commons Wikimedia  
2.”7152514131″ by Vivien Rolfe (CC BY-SA 2.0) via Flickr