Microplate Readers vs. Spectrophotometers

Microplate readers and spectrophotometers are two valuable yet often misunderstood instruments in a lab. Both can help you analyze how light interacts with a sample by measuring the intensity and wavelength of the light that passes through a sample.

However, spectrophotometers and microplate readers are each geared toward a different purpose, with specific strengths and weaknesses. With subtle design differences, one is ideal for high-throughput operations, while the other is best for high-precision, single-sample analysis.

Their variations can affect your measurements, workflow and throughput, so choosing the right one for your lab and application is essential. To help you decide, we'll compare spectrophotometers and microplate readers and review some common questions.

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What Is a Spectrophotometer?

To measure optical characteristics, a spectrophotometer fires a beam of light through a sample and detects it on the other side. The intensity and wavelength of this beam allow the instrument to determine how the light interacted with the sample. For instance, it might measure how much light the sample absorbed or transmitted.

You can find spectrophotometers that operate on the ultraviolet-visible (UV-Vis) or infrared (IR) spectrums. The wavelengths in the UV-Vis spectrum range from about 185-700 nanometers, while an IR range spans 700-150,000 nanometers.

Spectrophotometers typically have four primary components:

  • A light source
  • A monochromator that selects the appropriate wavelength
  • A sample holder
  • A detector

Spectrophotometers can typically only measure one sample at a time in a cuvette. Still, they're highly precise, and you can find them in many different types of labs, from those in the pharmaceutical industry to food production and environmental testing. They support quantitative analysis in nearly every discipline, including chemistry, biology, material engineering and clinical applications.

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What Is a Microplate Reader?

What Is a Microplate Reader?

As a specialized type of spectrophotometer, a microplate reader also aims to measure how light interacts with a sample. Plate readers can take a wide range of measurements, such as absorbance, fluorescence, luminescence and time-resolved fluorescence, and the samples are held in a microplate, a flat tray filled with small wells. 

Microplates typically contain 96-384 wells, but some large models can support over 1,000 or even 9,600 wells. This size gives it the advantage of providing higher throughput and speed, a must-have for some analysis or production tasks.

The microplate's design also creates one big caveat — the instrument is very sensitive to sample sizes, which should be exactly the same in each well. Inconsistent sample sizes can cause inaccurate measurements. To avoid this, most labs use manual or automatic liquid handling systems to distribute the samples evenly. Some instruments include shaking features to help remove bubbles and improve consistency.

One of the most prominent uses for microplate readers is enzyme-linked immunosorbent assay (ELISA) testing. ELISA testing is primarily used in immunology to detect and measure antibodies, proteins, antigens and glycoproteins in biological samples. It's a popular diagnostic tool well-suited to the high-throughput and various detection modes of plate readers.

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What Is the Difference Between a Microplate Reader and a Spectrophotometer?

Both instruments aim to measure light and typically use either a monochromator system or filter-based optics, but they differ in the number and size of samples, precision levels and the direction of the light beam. A spectrophotometer offers higher dynamic range and precision and is less sensitive to inconsistencies in sample sizes, but a microplate reader supports more samples at once, making it crucial for high-throughput operations.

Sample Sizes

One of the most noticeable differences between these two instruments is the larger number of wells in the microplate reader. A spectrophotometer only supports one sample at a time, typically about 1-2 microliters. In comparison, a microplate reader can accommodate much larger sample sizes and read hundreds of samples at once.

The higher throughput of a plate reader is ideal for production tasks and narrowing down a large collection of samples. For example, if you're looking for a specific measurement, you might run a plate reader with many samples. Then, whichever one meets your criteria can move on to the spectrophotometer for more detailed analysis.

The plate reader is also good for comparing samples and duplicating results. In labs with fewer or more sporadic demands, a spectrophotometer might be more cost-effective.

The Direction of Light Beams

These instruments also use different methods of measuring light.

A spectrophotometer passes the beam through the sample horizontally, and the cuvette essentially standardizes the path the light must travel to about 1 centimeter. This design contributes to the instrument's high precision, but it can also lead to artifacts and other elements that could make it harder to understand the results. Sophisticated software can help clear things up.

In comparison, microplate readers send the light beam vertically and don't have the same standardization a cuvette offers. Because the design passes through multiple wells, the volume of the sample in each well will affect the path of the light, necessitating careful liquid handling techniques.

Automation and liquid handling systems can help achieve this high level of consistency and precision, but they add to the complexity of the plate reader. Labs also must consider the need for washing and maintaining these components and how it might affect the workflow.

Is a Microplate Reader a Spectrophotometer?

Yes, a microplate reader is a type of spectrophotometer. It's a specialized model designed for handling multiple samples, mainly when using ELISA techniques. With the design variations we've just mentioned, however, the two aren't entirely interchangeable.

Is a Spectrophotometer More Accurate Than a Plate Reader?

A spectrophotometer can generally achieve a higher dynamic range than a microplate reader, but many variables are at play with both instruments. Because the cuvette of a spectrophotometer helps to standardize the sample size, it's easier to achieve consistent results with one. Even if the sample volume varies from test to test, the light still only crosses the same length of the cuvette, producing reliable measurements.

Although microplate readers are quite reliable, the sample sizes must be exact in every well. If the volume varies, the light beam might pass through more or less material. The need for automatic or manual liquid handling systems adds more variables that can contribute to inconsistencies. In short, there's more opportunity for error in a plate reader.

Get the Instrument You Need From New Life Scientific

Get the Instrument You Need From New Life Scientific

Depending on your application, either a spectrophotometer or a microplate reader could be right for your lab. Really, you might even need both! At New Life Scientific, our large selection of used instruments allows you to find the right one for your lab and move your science forward. Our trusted team is ready to help you with your selection and set you up with ready-to-ship equipment backed by a 120-day warranty.

Shop our spectrophotometers and microplate readers online, or reach out to us for assistance!