What Is a Colorimeter?
Colorimeter is a generic term for measurement instruments in which the colorimetric method is used.
Spectrophotometers that measure transmittance and absorption of light at a certain wavelength are commonly used. Colorimetry is a method of measuring concentration by adding a special reagent to various test samples, causing them to develop a color, and comparing the change in the color itself and the intensity of the color.
In water quality research, this method is used to measure residual chlorine concentration, pH, turbidity, residual nitrogen, and oxygen concentration. In the field of scientific research, it can also be used to determine the precise concentration of a sample.
Uses of Colorimeters
In general water quality testing, the following items are used for precise measurement by adding special reagents to the collected water and causing it to develop a color.
- Residual chlorine concentration measurement
- pH measurement
- Turbidity measurement
- Residual nitrogen measurement
- Oxygen concentration measurement
In air pollution surveys, nitrogen oxide and carbon dioxide concentrations can be measured by washing the test probe with a certain amount of aqueous solution after exposure to air and then performing a colorimetric test on the solution.
Colorimeter assays are used for a variety of water quality studies and air pollution investigations, and with the proper selection of the wavelength of incident light, it is also possible to determine the concentration and amount of specific substances in a sample.
Principle of Colorimeters
A Colorimeter is designed to measure the intensity of light transmitted through a sample by incident light. The transmitted light intensity of the solution to be used as the standard sample is measured in advance, and then the sample is measured.
The ratio of the transmitted light intensities of the two samples is taken as the measurement value, and the Colorimeter can be used to measure the transmittance, turbidity, and absorbance of the sample.
Structure of Colorimeter
A spectrophotometer, one of the most widely used Colorimeters, consists of the following components:
- Light source
- Slit
- Condenser lens
- Monochromator
- Sample holder
- Photodetector
- Measuring instrument
- PC
For large instruments such as those used for research, dedicated analysis software may be used.
Types of Colorimeters
1. Types of Colorimeters
This instrument is used to measure the absorption or reflection spectrum of a substance. Light from a light source is absorbed or reflected by a substance and the resulting spectrum is measured. This allows us to analyze the color and chemical properties of a substance.
2. Color Meter
An instrument that uses light of a specific wavelength to measure the color of a substance. It quantifies the color of a substance based on whether it absorbs or reflects light.
Also called a colorimeter, chromimeter, or color difference meter, it is suitable for making relatively simple measurements and is often used in the fields of education and quality control.
3. RGB Colorimeter
Designed based on the human visual system, Colorimeters use sensors with sensitivity similar to that of the human eye to measure the color of a substance. This allows the calculation of key color characteristics such as RGB values and CIE chromaticity coordinates.
4. PH Colorimeter
This Colorimeter uses a dedicated test solution to measure pH in terms of the color developed. Some meters can measure pH with the same accuracy as a glass electrode pH meter. They are often used to measure the pH of soil and water.
5. Portable Colorimeter
Portable Colorimeters are compact, lightweight, and portable. They can be carried to a variety of locations, making them versatile and useful. Their low price and high convenience make them ideal for on-site work.
On the other hand, its small size may result in inferior measurement accuracy and a narrow measurement range. Also, when used outdoors, ambient light is likely to affect measurement values.
Other Information on Colorimeters
Beer-Lambert Law
Colorimeters irradiate light onto a sample and measure the intensity of the transmitted light. The measured intensity can be calculated using the Beer-Lambert formula to obtain absorbance, a dimensionless quantity that represents light intensity.
Beer-Lambert’s formula: A = – log10 (I1/I0) = ECl = εcl
- Absorbance: A
- Intensity of incident light: I0
- Intensity of transmitted light: I1
- Specific absorbance: E
- Concentration: C
- Length of medium: l
- Molar absorbance: ε
- Molar concentration of the medium: c