Single-Beam Spectrophotometer; Instrumentation, Working, Advantages, and Disadvantages


Spectrophotometers determine the wavelength distribution of light by reporting the percentage of reflectance from an item and identifying the sample’s color.

The two different kinds of beam spectrophotometers do exist in the market

  • Single-beam spectrophotometer
  • Double-beam spectrophotometer

When determining which of these devices is suitable for your laboratory, you should look at their main distinctions.

single beam spectrophotometer

What is a Single-Beam Spectrophotometer and How Does It Work?

An analytical device known as a single-beam spectrophotometer allows all of the light waves emanating from the light source to pass through the sample. Since light intensity changes as it goes through the sample, measurements are made as it does. 

A spectrophotometer must first be calibrated by using standard solutions with the solute of known concentration in the test solution. For this, the Cuvettes are filled with the standard solutions and set in the Cuvette holder of the spectrophotometer.

Single-beam spectrophotometers use a single light beam from a light source to illuminate both the sample and the reference sites. The light wavelength that is employed in this situation is chosen by the monochromator.

single-beam spectrophotometer

A single-beam spectrophotometer can precisely quantify Nucleic acid and purified proteins in the same UV region. It counts how much of a radioactive analyte is present in a sample. This is accomplished by calculating the number of light beams absorbed by that component within the specimen.

In this case, the Beer-Lambert Law can be used to measure the light beam. This law states that the absorbance factor in the samples is directly proportional to the concentration of an analyte in the samples.

The Basics of Single-Beam Spectrophotometer Instrumentation

Three separate light sources are frequently utilized to create light with various wavelengths in spectrophotometers. A tungsten lamp is the most typical type of light source used in spectrophotometers for the visible spectrum.

Familiar sources of ultraviolet radiation include the deuterium lamp and the hydrogen lamp. The best sources of infrared (IR) radiation are Nernst filaments or globals.

The monochromatic light that enters the Cuvette is partially reflected, partially absorbed by the solution, and partly transmitted through the solution before striking the photodetector system. The transmitted light intensity is calculated by the photodetector system and converted into electrical impulses.

These electrical impulses are measured by the galvanometer, which then digitally displays the results. The solution under analysis has an absorbance or optical density, which is a digital representation of the electrical impulses.

More light will be absorbed with a higher absorption rate, and more light will be transmitted through a solution with a lower absorption rate. It influences the galvanometer reading and reflects the solute concentration in the solution.

single-beam spectrophotometer

Single Beam Spectrophotometer: Understanding the Advantages and Disadvantages


  1. Improved efficiency
  2. High sensitivity for detection
  3. More affordable
  4. Simplistic in its design
  5. Convenient to use
  1. It does not account for errors like voltage fluctuations that affect the outcomes
  2. Only counts the absorbance of either the sample or the reference blank at one time


A single-beam spectrophotometer is a type of analytical instrument that is used to measure the absorption of light by a sample. It consists of a light source, a monochromator to select the desired wavelength of light, a sample holder, and a detector to measure the intensity of the light after it passes through the sample.

The sample is placed in the sample holder and the spectrophotometer measures the amount of light that is absorbed by the sample at a specific wavelength. The result is typically expressed as the absorbance of the sample, which is a measure of how much the sample absorbs light at a particular wavelength.

A single light beam with a wavelength of between 325 nm and 1000 nm is employed. The test solution and blank are read in the same direction since the light can only move in one direction. It is ideal for measuring light transmittance or absorbance at a particular wavelength. It is not for full-band spectrum scanning. Because it demands an increased light source and detector stability.

Single-beam spectrophotometers are commonly used in a variety of applications, including chemical analysis, biomedical research, and environmental monitoring.


What is absorbance and how is it measured?

Absorbance is a measure of how much a substance absorbs light. It is measured by comparing the intensity of the light before it passes through the sample to the intensity of the light after it passes through the sample. The absorbance is then calculated using the Beer-Lambert Law, which states that the absorbance of a substance is directly proportional to the concentration of the substance and the path length of the light through the sample.

What are the advantages of using a single beam spectrophotometer?

One advantage of using a single beam spectrophotometer is that it is relatively simple and easy to use. It is also less expensive than other types of spectrophotometers, such as double beam spectrophotometers. Additionally, single beam spectrophotometers can be used to measure a wide range of wavelengths, making them versatile for a variety of applications.

What are some common applications of single beam spectrophotometers?

Single beam spectrophotometers are commonly used in a variety of fields, including chemistry, biology, and environmental science. Some common applications include analyzing the concentration of chemical compounds in solutions, studying the purity of drugs, and measuring the pH of a sample. They are also used to analyze the composition of food and beverages, such as wine and beer.

What is difference between single beam and double beam spectrophotometer?

The main difference between a single beam and a double beam spectrophotometer is the way that they measure the absorbance of a sample. A single beam spectrophotometer measures the absorbance of a sample by comparing the intensity of the light before it passes through the sample to the intensity of the light after it passes through the sample. A double beam spectrophotometer, on the other hand, uses two separate light beams: one that passes through the sample and one that does not. The absorbance of the sample is then calculated by comparing the intensities of the two beams.


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