Spectrometer vs Spectrophotometer

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The spectrophotometer and spectrometer are two integral instruments in spectroscopy. The terms "spectrometer" and "spectrophotometer" are frequently used interchangeably, especially when discussing optical spectrometers. Both instruments can split light into constituent wavelengths and measure intensity at specific wavelengths. Typically, spectrophotometers are referred to more often in biological, life sciences and chemistry, where as spectrometer (or optical spectrometer) is the general term used in physical sciences.

One key difference between these instruments is in their working principles. In spectrophotometers, the diffraction grating, the component used to disperse split incoming light, rotates. As the grating rotates, different wavelengths are sequentially directed onto a single pixel detector.  However, spectrometers use a fixed diffraction grating, and an multi-pixel array detector, capable of distinguishing between wavelengths based on their position on the sensor. All the disperse light hits the detector at once, and the intensity of all wavelengths is measured simultaneously.

 Spectrophotometers tend to be large, enclosed units, containing many different components (for example, dispersion typically happens within a monochromator). A spectrometer can is much smaller and can be integrated with other optics components on an optical bench.

Spectrometer vs Spectrophotometer Definition

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"Spectrometer" is a general term for a piece of equipment that can separate and measure spectral components of a physical phenomenon. Spectrometers can be designed to measure various phenomena such as electromagnetic light, mass, or nuclear magnetic resonance. This includes many tools including mass spectrometers, NMR spectrometers and, in this definition, spectrophotometers. However in optical spectroscopy, the terms spectrometer is most often used referring to an optical spectrometer like the Ossila USB Spectrometer.

Our research shows that there is not one firm definition for a spectrophotometer, and its usage or purpose varies. Referring to both spectral ("spectro") and light ("photo") components, one common definition states that a spectrophotometer is an instrument used to measure the intensity of light absorbed by a sample. 

Spectrophotometer vs Spectrometer Components

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While spectrometers and spectrophotometers are both designed to measure light across different wavelengths, their internal components highlight their different functionalities and applications. Spectrometers and spectrophotometers typically consist of the following components:

	Spectrometer	Spectrophotometer
Components	Entrance slit Diffraction grating Multi-pixel sensor	Light source Adjustable slits Monochromator (including diffraction grating) Sample holder Single pixel detector
Diffraction Grating Type	Fixed	Rotating
Light Source Included?	No	Yes
Sensor Type	Multipixel array (CCD or CMOS)	Single-Pixel photodetector
Unit Size	Compact	Larger
Extra Components Needed for Measurement	Light source Sample holder Optical fibers	None
Measurement Acquisition	Entire spectrum at once	Intensity of transmitted light at specific wavelengths

Spectrometers can record an entire spectrum in a single acquisition, making them ideal for real-time monitoring. These are often compact systems (like the USB spectrometer), and integration into optical benches or experimental setups.

Alternatively, the spectrophotometer configuration enables precise measurements of absorbance or transmittance at discrete wavelengths, which is particularly useful in analytical chemistry and biological applications.

In essence, spectrometers are built for speed and compactness, while spectrophotometers are optimized for high-accuracy measurements at specific wavelengths.

Key Differences Between Spectrometer and Spectrophotometer

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• Design and Modularity

  Spectrophotometers are typically self-contained units with fixed components, with a light source and optical components included. In contrast, spectrometers are often modular and can be used in combination with a range of sample holders and light sources. Spectrometers, like our USB Spectrometer, are commonly part of modular setups where light sources are sold separately.

• Sample Handling

  Spectrophotometers are designed for specific purposes and samples, often requiring designated sample holders. They are usually designed to measure liquid samples in standard cuvettes like the Ossila Quartz cuvette. Spectrometers, on the other hand, can accommodate many different sample cells and configurations, allowing measurements under various conditions, including different temperatures.

Applications and Uses

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As stated, the term spectrometer can be used interchangeably with spectrophotometer. Some definitions describe a spectrophotometer as a spectrometer used for specific absorbance measurements specifically. Others say that spectrophotometry is the act of measuring a material with a spectrometer.

Spectrophotometers are often associated with life sciences, medicine, and biological applications. Specifically, they are used to measure absorbance or transmittance of light, either at specific wavelengths, particularly in biosensors, DNA analysis, and biological reaction studies, or over a range of wavelengths for molecular identification or other optical studies. By measuring these properties, spectrophotometers can determine the concentration or optical density of a material or a biological sample.

Benchtop spectrometers on the other hand, are used for quick and simple optical measurements. They can simultaneously measure the intensity of light at different wavelengths, providing valuable information about the distribution of wavelengths in a given sample or light source.

The term "spectrophotometer" is sometimes used to describe a handheld device specifically designed for color measurement. These spectrophotometers are used in a field of spectroscopy called colorimetry, which focuses on quantitatively measuring the color of light. Taking accurate color measurement is very important for various industries, such as in designing pigments and dyes, when characterizing LEDs and within the food industry.

Choosing the Right Instrument

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When selecting between a spectrometer and a spectrophotometer, consider the specific requirements of your application. If you are taking one measurement consistently, e.g., you are measuring absorbance or transmittance of light at specific wavelengths in biological samples, a spectrophotometer may be more suitable for your needs. For broader measurements of light intensity across various wavelengths or applications in chemistry and physics, a spectrometer would be a better choice.

Understanding the distinctions between spectrometers and spectrophotometers will help you make an informed decision and ensure that your instrument meets your research needs.

A spectrometer is a device that measures a continuous, non-discrete physical characteristic by separating it into a spectrum of its constituent components. The study of this data is known as spectroscopy. Different types of spectrometer measure different characteristics. The most common type of spectrometer, the optical spectrometer, measures the properties of light over a defined range of the electromagnetic spectrum.

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