Double Beam Spectrophotometer: Instrumentation, Working, Advantages, and Disadvantages


Spectrophotometers are an example of an optical device that uses a characteristic of light rays to determine a specific wavelength.

Two different kinds of beam spectrophotometer, Single-beam spectrophotometer, and Double Beam Spectrophotometerer, do exist in the market.

Based on their chemical structures, concentrations, etc., the analyte present in biological specimens absorbs a particular wavelength of light rays, which enables scientists to establish the presence of chemical species there.

This equipment accurately measures the absorption characteristics. In the research and scientific lab, visible instruments are used in a wide range of settings.

However, Mass Spectrometry is also a powerful analytical technique that provides precise molecular weight information and molecular structure identification, revolutionizing the fields of chemistry and biology.

Principle of A Double Beam UV-Visible Spectrophotometer

The wavelength range of a double-beam Uv-Vis spectrophotometer is 185 to 1000 nm. This device divides the monochromator’s light output into two beams.

Both the reference beam and the sample reading beam are employed.

Different areas of the two light beams are illuminated and radiated. The entire set of samples is radiated from the second part, while the first part illuminates the reference

It removes the inaccuracy that results from variations in the light output and the detector’s sensitivity.

Reference Beam

This beam is used to measure lamp energy by passing through the reference standard.

Sample Beam

To reflect sample absorption, this beam travels through the sample.

Double beam spectrophotometer

Before they reach a single monochromator device connected to the optical instrument, the light beams may be merged again following excitation.

Two monochromators are employed in spectrophotometry under particular circumstances. The dispersion, reflection, and refraction of light are the fundamental concepts behind a standard double-beam spectrophotometer.

Using these techniques, one can calculate the findings of analytes present in a biological sample based on their absorption properties.

Using a Double Beam Spectrophotometer to Analyze Organic Compounds

A substantial amount of radiation must be absorbed by the atom in the double-beam UV-visible spectrophotometer before it can move from the ground state to an excited state and proceed to higher excited states.

In the context of spectrophotometry, the term “absorption” refers to the actual physical act of absorbing light, whereas “absorbance” refers to a sample’s capacity to do so. In single-beam and double-beam spectrophotometers, it may also detect the attenuation of the instrument’s lens, which is brought on by absorption.

The wavelength of the primary incident light affects the diffraction angles in this device. The apparatus has disks that aid in the formation of the diffraction angles. As a result, measurements of the biochemical components in the sample can be made more accurately.

Double beam spectrophotometer-

Through the specimens, light diffraction takes place. The refraction of light improves the reproducibility of the spectrophotometry procedure.

A fraction of the mixed wavelengths are absorbed when white light passes through the sample and is reflected by a colored substance. The complementary hue to the wavelength of the light that was absorbed will be assumed for the remaining light beam.

The color spectrum serves as evidence for this phenomenon.

Double Beam Spectrophotometer: Advantages and Disadvantages

✅ It speeds up scanning across a broad
wavelength range.
It costs a lot.
✅ Adjusting the transmittance between
0% and 100% at each wavelength is
not necessary.
A double-beam spectrophotometer is
challenging to use.
✅ It concurrently displays the intensity
ratio of the sample and reference
✅ Radiation source fluctuations are kept
to a minimum

Price Range of Double Beam Spectrophotometer

The price range of a double-beam spectrophotometer can vary greatly depending on factors such as the manufacturer, specifications, and features. On average, a basic model can cost anywhere from $5,000 to $15,000, while high-end models can cost upwards of $50,000 or more. It is important to carefully consider the specific requirements for your application and to compare multiple products from different manufacturers to determine the best value for your budget.


In summary, a double beam UV-Visible spectrophotometer is a scientific instrument used to measure the absorption of light by a sample. It works by dividing the light output from a monochromator into two beams – the reference beam and the sample reading beam. The reference beam measures lamp energy while the sample beam reflects the sample’s absorption. The two beams are merged again before reaching a single monochromator device, allowing scientists to calculate the presence of analytes in a biological sample based on their absorption properties. The device uses the concepts of dispersion, reflection, and refraction of light to accurately measure the absorption characteristics. The double-beam spectrophotometer can be used to analyze organic compounds by determining their ability to absorb radiation.


What is a double-beam spectrophotometer?

A double-beam spectrophotometer is an optical device that measures the absorption characteristics of light by dividing the monochromator’s light output into two beams – the reference beam and the sample beam.

What is the wavelength range of a double-beam spectrophotometer?

The wavelength range of a double-beam UV-Vis spectrophotometer is 185 to 1000 nm.

What is the purpose of the reference beam and sample beam in a double-beam spectrophotometer?

The reference beam is used to measure lamp energy by passing through the reference standard, while the sample beam travels through the sample to reflect its absorption.

How does a double-beam spectrophotometer improve accuracy?

A double-beam spectrophotometer removes inaccuracies that result from variations in light output and detector sensitivity by illuminating different areas of the two beams

How is a double-beam spectrophotometer used to analyze organic compounds?

A double-beam spectrophotometer analyzes organic compounds by calculating their absorption properties, using the concepts of dispersion, reflection, and refraction of light. A substantial amount of radiation must be absorbed before the atom can move from the ground state to an excited state.

The Benefits of Double Beam Spectrophotometer in Industrial Settings

A double-beam spectrophotometer analyzes grains, liquids, powders, pellets, and opaque solids and provides a quick and accurate spectrophotometric result. Excellent sample volume capacity, a wide dynamic range, and lifetime use are all features of a high-quality double-beam spectrophotometer. The following materials and others are frequently examined using double beam spectrophotometers:

• Foodstuffs and drinks
• Pharmacological substances
• Clinical test specimens
• DNA examination
• Scanning for wavelengths
• Protein evaluation
• Quantitative examination of kinetics


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