# Colorimeter principle and procedure

A colorimeter is a light-sensitive tool used to measure the absorption and transmission of light passing through a sample solution. A colorimetric device works according to Beer Lambert's law. The photoelectric colorimeter is a sensitive device intended for use in various colorimetric analyzes such as analysis of soil components, building materials, analysis of water, food ingredients, textile products, additives and used in different manufacturing processes.

 ContentsWhat is the colorimeter?Principle of the colorimeterPrinciple of operation of the colorimeterType of colorimeterColorimeter procedureApplications of the colorimeterAdvantages of the colorimeterDisadvantages of the colorimeter

## Principle of the colorimeter:

Colorimetry is a sensitive tool used to determine the intensity and concentration of a sample at a given wavelength. Two types of colorimeters are commonly used: spectrophotometers and tristimulus colorimeters. The principle of the colorimeter works according to the Beer-Lambert law. This rule states that the absorption of light passing through a medium is directly proportional to the intermediate convergence. When using a colorimeter, there is a beam of light where a certain wavelength is directed at a liquid sample. When introducing a sample solution, the light beam passes through a series of different lenses and the microprocessor is used to determine the absorption or emission of light through the liquid sample. If the sample concentration is high, more light will be absorbed and if the sample has a low concentration, more light will be transmitted.

You can determine colorimetric reactions with a colorimeter or a spectrophotometer. Both measure the intensity of light passing through a liquid sample and convert the intensity of that light to a concentration based on a specific calibration curve.

The colorimetry follows the principles of the Beer-Lambert law and is expressed by:

A = Ɛxbxc

A is the absorbance of the sample component

Ɛ is a wavelength-dependent absorption coefficient

b is the cell path length

c is the concentration of the analyte

## Principle of operation of the colorimeter:

The principle of operation of the colorimeter depends on the Beer-Lambert law which states that the amount of light absorbed by a sample corresponds to the concentration of the sample solution and the length of the light path through the solution. A low voltage lamp which is illuminated by a constant voltage is the light source. This happens through a color filter and a liquid sample in the detector. Then the current generated by the photocell is converted into voltage to display the result on the screen. The current generated by the photocell will then be converted into voltage to display the result of an absorbance or a transmission on the screen.

## Type of colorimeter:

Tristimulus colorimeter and spectrophotometer are the types of colorimeter used for color measurement.

Tristimulus colorimeter: The trichromatic colorimeter is generally used for quality control, being suitable for color variations and determination of resistance. The tristimulus method measures the light reflected from the object to have similar sensitivity using three separate sensors.

Spectrophotometer : A spectrophotometer is a device that can determine the intensity of light based on the color, or more specifically, the wavelength of light and other liquid samples. This detects both the full UV spectrum in the 200-400nm range and the 400-800nm ​​visible range. It provides accurate data by providing the wavelength of absorbance or transmittance properties of the sample using wavelength spectral analysis. A spectrophotometer is simple and quick to use and is most often used to measure light absorption.

## Colorimeter procedure:

Before starting a colorimetric analysis, one must recognize the different parts that are essential to carry out the process.

Light source: A tungsten or xenon lamp is usually used to produce the light.

Filtered: It is made of colored glass and is used to detect narrow wavelength light.

Plateau: It is used to hold the sample solution. Monochromatic light passes through the sample solution placed in a cuvette. Cuvettes are made of quartz or special glass.

Detector or photocell: is used to detect light transmitted through the sample. It is the photosensitive component that transforms light energy into electrical energy.

### Colorimeter experimental procedure:

• A colorimeter requires initial calibration using standard solutions of the specified solute concentration to be measured in a test sample.
• Prepare the samples according to the procedure.
• Turn on the instrument and let it warm up for 10-15 minutes.
• Choose the right filter.
• Select the appropriate mode, i.e. % transmittance or absorbance.
• Insert the test tube containing the "Empty" or "Reference" solution.
• Autozero with blank solution.
• Remove the test tube containing the blank solution and introduce the sample solution.
• Note the reading in %T or optical density mode.

## Applications of the colorimeter:

• Used to confirm fabric and paint color quality and consistency
• Colorimeter applications have qualitative and quantitative analysis of samples.
• The food industry uses it to guarantee product quality.
• It is used to determine the quality of food, to ensure that it does not spoil by determining its particular color.
• It can also be used to calculate the path of a reaction by evaluating the rate of formation and disappearance of light-absorbing analytes in the visible light spectrum range.
• Water quality is measured by colorimetry.
• It is used by manufacturers of paints, pharmaceuticals and textiles.
• Colorimetry is frequently used to determine sample concentration by determining the transmittance, optical density, or absorbance of the sample.
• By determining the absorption spectrum in the visible range, the component can be identified.

## The advantages of the colorimeter are as follows.

• It's cost effective, fast and easy to use.
• Compared to volumetric or gravimetric methods, it is a fast and comfortable technique.
• No expert is required to manage it.
• Using the process of colorimetry, chemicals in water can be identified.
• He subjected colored compounds to quantitative analysis.
• It can be used in the quantitative analysis of colored compounds.
• Another advantage of the colorimeter is that it is a portable system that is easy to transport.

## The disadvantages of the colorimeter are as follows.

• Not analyzing colorless compounds is the main disadvantage of colorimetry.
• Requires larger amounts of samples for analysis.
• It requires the preparation of the standard solution.
• It has a lower sensitivity than other techniques.
• Colorimetry does not work in UV and IR regions.
• The precise bandwidth of wavelengths can be essential for more precise analysis of molecules.

### The most frequently asked questions about the colorimeter are as follows.

What is a colorimeter?

A colorimeter is a light-sensitive tool used to determine the emission and absorption of light passing through a sample solution.

What are the types of colorimeters?

Two types of analysis are used in colorimetry: the spectrophotometer and the tristimulus colorimeter.

What light source is used in the colorimeter?

Generally, a tungsten or xenon lamp is used as the light source in colorimetry.

What is the main advantage of the colorimeter?

The main advantage of the colorimeter is that it is cheap, fast and easy to use.

What is the main difference between spectrophotometer and colorimeter?

The main difference between a spectrophotometer and a colorimeter is that the spectrophotometer determines absorbance, or transmittance as a function of wavelength, and can operate over a range of wavelengths, i.e. UV or VIS, while a colorimeter is a tool that determines the absorption of particular particles. colors at a fixed wavelength.

What is the main difference between absorbance and transmittance?

The main difference between absorbance and transmittance is that absorbance determines the amount of light absorbed by the analyte when a light beam passes through it. While transmittance is the amount of light transmitted by the analyte when a beam of light passes through it.

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