What Is a Colorimeter?
The colorimeter is a device used for colorimetry. It measures the absorbance and transmittance of light waves through a liquid sample. The amount of light transmitted or absorbed by the sample gives the concentration of a known solute in a test solution based on Beer-Lambert’s law.
Figure: The diagram of a colorimeter.
The main components of a colorimeter are:
- Illuminant: It’s a fixed light source that passes through the object during the experiment.
- Photocell: It detects the amount of light passing through the sample.
- Cuvette: It’s a cubical-shaped sample holder in which samples are kept for analysis.
- Standard observer: It’s a two-degree, small, and specific field of view.
- Tristimulus absorption filter: This filter isolates specific wavelengths to be applied to a sample.
- Detector: It converts the transmitted light into an electrical signal once it passes the sample container or cuvette.
Figure: The detailed diagram of all parts of a colorimeter.
Types of Colorimeters
1. Based on Size
- Benchtop colorimeter: It’s a big machine requiring a benchtop for its setup. It’s highly accurate and comes in the wavelength range of 420-660 nm. The device is most suitable for lab experiments.
- Portable/handheld colorimeter: This compact device can be carried anywhere and is mainly for outdoor settings for food and water sample analysis.
2. Based on Filters
- Tristimulus colorimeters: It’s one of the commonest filters in colorimeters. It has three filters for measuring the intensity of three primary colors: red, green, and blue.
- Spectrophotometer colorimeters: They are used to measure the spectral distribution of light sources. It has a prism that breaks the light into a spectrum of colors.
- Densitometer colorimeters: They contain a single filter to measure the color intensity of a specific light. It’s mainly used for yeast and bacterial growth studies.
3. Based on Display
- Analog colorimeter: It has an upper number scale to show transmittance and a lower number scale for absorbance.
- Digital colorimeter: The digital device has an LED screen that displays absorbance and % transmittance in digits. It’s preferable by researchers over analog colorimeters.
Applications of Colorimeter
Colorimeters have wide applications in pharmaceutical, food and beverage, and clinical industries and labs. These are:
- Used in clinical labs for urine, serum, cerebrospinal fluid, and plasma analysis for biochemical studies.
- In the food industry, the device can measure the concentrations of harmful toxins and preservatives in food and beverage samples.
- Densitocalorimeter is used in microbiology labs to study the growth density of yeast and bacterial cultures.
- Used to analyze the spectrum of colors in the paint and textile industries.
- The device has major applications in quality control. It’s widely used to test the quality of water samples in water supply areas and drugs manufactured by pharma companies.
- Forensic labs use colorimeters to analyze different samples.
- In agriculture, the device has applications in measuring soil nutrients and their fortification level.
- The colorimeter is also used in the quantitative analysis of glucose, proteins, and other biochemical compounds.
- Used in the determination of hemoglobin in blood samples.
Factors To Consider When Buying a Colorimeter
Here’re some factors to consider if you want to purchase the right colorimeter design for your lab:
- Application and Lab Space: It’s essential to consider the purpose you want the device for and its portability. Benchtop calorimeter is best for lab applications, while portable devices are perfect for industrial visits and quick analysis of different samples.
Figure: Portable Colorimeter.
- Color Quality Control: Different industries have different requirements for color difference accuracy, and colorimeter devices have different values. For example, handheld colorimeters have a high accuracy, when the ΔE*ab is within 0.08.
- Budget: Many colorimeter designs are available with a spectrum of features. Thus, it’s essential to consider your budget while buying a device with features matching your lab requirements.
- Analog or Digital: Based on the frequency of experiments performed in the lab and your budget, you can choose which one suits best for your lab. The digital instrument might be more expensive than analog, however, it offers more ease to researchers.
What Is a Spectrophotometer?
The spectrophotometer is an instrument for performing quantitative analysis of a test sample based on the amount of light absorbed by its colored compounds.
By measuring how much light is absorbed by a sample when a light beam passes through it, we can determine the concentration of a particular molecule or compound.
Figure: An illustrative diagram of the principle of the spectrophotometer.
The main components of a spectrophotometer include:
- Spectrometer: It produces light of a particular wavelength.
- Photometer: It measures the intensity of light when a light beam is passed through the sample.
- Light Source: It produces light of various wavelengths required for the experiments.
- Sample Chamber: It holds the sample container.
- Monochromator: It refracts light into a single spectrum, dispersing polychromatic light into its essential wavelengths.
- Detector: When the light beam is passed through the sample, the photometer detects the intensity, and the signal galvanometer displays the values.
- Digital Display: It shows the amount of light absorbed by the sample or any other information captured by the machine.
Types of Spectrophotometer
- VIS spectrophotometer: It measures absorbance and conducts quantitative analysis at visible wavelengths (400 ~ 760nm).
- UV-VIS spectrophotometer: It measures absorbance and performs quantitative analyses of material at visible and ultraviolet wavelengths (200 ~ 760nm)
- Infrared spectrophotometer: The device measures the absorbance of the sample in the infrared spectrum, a wavelength >760 nm.
- Fluorescence spectrophotometer: An instrument that scans the fluorescence spectrum generated by liquid fluorescent labels. It’s mostly used in food testing, scientific research, and clinical tests.
- Atomic absorption spectrophotometer: It analyzes metal elements by measuring the characteristic radiation absorption of their atomic vapors.
Applications of Spectrophotometers
Spectrophotometers have applications in industrial and commercial sectors, such as:
- It’s used for many biochemical experiments, including the isolation of DNA, RNA, and proteins, enzyme kinetics, and biochemical analysis.
- For quality control testing on raw materials, intermediates, and final products. It helps to validate the purity of the compound and find any impurities present in it.
- Commonly used to analyze water quality, clarity, and purity. The measurement of water quality has many important uses, such as detecting heavy metals in drinking water, measuring pollution levels in wastewater, and verifying water purity for laboratory tests.
- To determine the formation and disappearance rates of light-absorbing compounds in the visible and UV spectrums. Also, it identifies compounds based on their absorption spectrums in the visible and UV regions of the electromagnetic spectrum.
Factors to Consider When Buying a Spectrophotometer
- Applications: You need to select the right spectrophotometer depending on your applications. For example, different experiments require different wavelengths for sample analysis.
- Specifications: Determine what features you need in your instrument, including detection limits, wavelength range, and custom options.
- Budget: How much are you willing to spend on your instrument? Compare the prices of different manufacturers and look for financing options they have to offer their customers.
- Space Requirement: Spectrophotometers are available in portable and a spectrum of benchtop designs. Thus, based on your applications and lab space, buy the instrument that best fits it.
Difference Between a Spectrophotometer and a Colorimeter — Which Is Better to Purchase?
Though colorimeters and spectrophotometers operate similarly, many differences exist between them. Here’s how they differ:
It measures how much light is absorbed by a particular solution.
Light intensity is measured by transmittance based on color or wavelength
It offers psychophysical analysis
It provides results by physical analysis
Less complex design, lightweight, and rugged
Heavy machine and more complex design
In colorimetric data, tristimulus values XYZ, G, b, d, etc. are directly read and displayed
Spectrophotometers can indirectly determine psychophysical characteristics
Works only with visible light
The device works with visible light, as well as infrared and ultraviolet light.
Considering the difference, choose the device that better matches your applications and requirements.
Colorimeters and spectrophotometers are instruments used to analyze test samples by passing a light beam of a particular wavelength through the samples. Both instruments have a spectrum of applications in labs, industries, and clinical areas to analyze water, blood, nucleic acid, and other similar compounds.
Even with similar operations, both instruments have many differences in terms of applications, wavelength function, and design. Thus, while choosing a spectrometer or colorimeter, one needs to consider many factors like design, purpose, space, and budget.
Check out our advanced benchtop spectrophotometer if you’re looking for the best.
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