Technical Note | ABSOR.B™
The modern and affordable solution to measure absorbance at specific wavelengths
by Dimitria Camasão,
Application Scientists, Rheolution Inc.
Absorbance is a crucial concept in the field of spectrophotometry, a technique used to measure the amount of light absorbed by a substance over a large range of wavelengths. It is a dimensionless quantity derived from the logarithm of the ratio of incident light to transmitted light through a sample. The absorbance spectrum, often represented as a graph, reveals the wavelengths at which a substance absorbs light most strongly (Figure 1). This information is useful in various scientific fields such as biology, chemistry, biochemistry, molecular biology for identifying and quantifying specific compounds or molecules in a sample.
Figure 1: Absorbance spectrum of the methylene blue solution.
The ABSOR.B™ is part of Rheolution’s CASCAD.S™ family of optical instruments. This modern instrument measures the light absorbed by a substance at discrete wavelengths using interchangeable optical cartridges emitting monochromatic lights. Values of absorbance at a particular wavelength are widely used in chemical and biochemical analysis to quantify the concentration of a substance in solution or to monitor reactions over time. The different emission cartridges (such as Emitt.405, Emitt.520, Emitt.635, Emitt.850) allow the user to select the proper wavelength for the given substance. In addition, measurements can be continuously collected and stored in the Soft Matter Analytics™ App which can control multiple ABSOR.B™ units.
Absorbance and transmittance of methylene blue at discrete wavelengths with ABSOR.B™
Methylene blue is a salt used as medication in clinics and as a dye in laboratory for hematology, immunohematology and clinical microbiology to stain cells and genetic material. Its peak absorption is at 668 and 609 nm (Merck Index). Different concentrations of methylene blue in deionized water were tested in the ABSOR.B™ using 1-mL clear glass vials and the Emitt.405, Emitt.520, Emitt.635, Emitt.850 cartridges.
Figure 2 shows average results ± standard deviation (three different samples per concentration tested, n=3). As expected from the spectrum (arrows on Figure 1), the red light (635 nm) was strongly absorbed followed by a slight absorption of the green light (520 nm). Violet-blue (405 nm) and infra-red (850 nm) lights had nearly zero absorption over the range of concentrations studied.
The relationship between absorbance and concentration is linear according to the Beer-Lambert Law, assuming that the solution is not too concentrated and that the incident light is monochromatic. The linear relationship obtained with the red light can be used to determine the concentration of methylene blue in an unknown solution.
In accordance with the absorbance results, the transmittance of the red light (635 nm) decreased as the concentration of methylene blue in solution increased. At 10 mg/L, less than 10% of light was transmitted. The transmission had a slight decrease for the green (520 nm), violet-blue (405 nm) and infrared (850 nm) lights (always higher than 85 %).
Figure 2: Absorbance and transmittance of methylene blue as a function of concentration (in mg/L) using the Emitt.405, Emitt.520, Emitt.635, and Emitt.850 optical cartridges in the ABSOR.B™ (n=3, error bars included but not visible).
These results also illustrate the high repeatability of the measurements (error bars included but not visible) with standard deviations always lower than 5 %. Overall, ABSOR.B™ is a modern and affordable instrument to precisely determine the concentration of different solutes using the proper wavelength.
KEY TAKEAWAYS
- The versatility of the ABSOR.B™ allows the user to use the same instrument to measure the absorbance and transmittance of different solutions by selecting the proper wavelength through the variety of available cartridges.
- Calibration curves from standard samples can be stored into the Tablet App for a quick determination of the solution’s concentration.
- The modularity of the ABSOR.B™ allows the user to expand their testing platform as the needs evolve with multiple units, different cartridges for light emission and reception, and sample holders.
$7,500 per system
Absorbance is a crucial concept in the field of spectrophotometry, a technique used to measure the amount of light absorbed by a substance over a large range of wavelengths. It is a dimensionless quantity derived from the logarithm of the ratio of incident light to transmitted light through a sample. The absorbance spectrum, often represented as a graph, reveals the wavelengths at which a substance absorbs light most strongly (Figure 1). This information is useful in various scientific fields such as biology, chemistry, biochemistry, molecular biology for identifying and quantifying specific compounds or molecules in a sample.
Figure 1: Absorbance spectrum of the methylene blue solution.
The ABSOR.B™ is part of Rheolution’s CASCAD.S™ family of optical instruments. This modern instrument measures the light absorbed by a substance at discrete wavelengths using interchangeable optical cartridges emitting monochromatic lights. Values of absorbance at a particular wavelength are widely used in chemical and biochemical analysis to quantify the concentration of a substance in solution or to monitor reactions over time. The different emission cartridges (such as Emitt.405, Emitt.520, Emitt.635, Emitt.850) allow the user to select the proper wavelength for the given substance. In addition, measurements can be continuously collected and stored in the Soft Matter Analytics™ App which can control multiple ABSOR.B™ units.
Absorbance and transmittance of methylene blue at discrete wavelengths with ABSOR.B™
Methylene blue is a salt used as medication in clinics and as a dye in laboratory for hematology, immunohematology and clinical microbiology to stain cells and genetic material. Its peak absorption is at 668 and 609 nm (Merck Index). Different concentrations of methylene blue in deionized water were tested in the ABSOR.B™ using 1-mL clear glass vials and the Emitt.405, Emitt.520, Emitt.635, Emitt.850 cartridges.
Figure 2 shows average results ± standard deviation (three different samples per concentration tested, n=3). As expected from the spectrum (arrows on Figure 1), the red light (635 nm) was strongly absorbed followed by a slight absorption of the green light (520 nm). Violet-blue (405 nm) and infra-red (850 nm) lights had nearly zero absorption over the range of concentrations studied.
The relationship between absorbance and concentration is linear according to the Beer-Lambert Law, assuming that the solution is not too concentrated and that the incident light is monochromatic. The linear relationship obtained with the red light can be used to determine the concentration of methylene blue in an unknown solution.
In accordance with the absorbance results, the transmittance of the red light (635 nm) decreased as the concentration of methylene blue in solution increased. At 10 mg/L, less than 10% of light was transmitted. The transmission had a slight decrease for the green (520 nm), violet-blue (405 nm) and infrared (850 nm) lights (always higher than 85 %).
Figure 2: Absorbance and transmittance of methylene blue as a function of concentration (in mg/L) using the Emitt.405, Emitt.520, Emitt.635, and Emitt.850 optical cartridges in the ABSOR.B™ (n=3, error bars included but not visible).
These results also illustrate the high repeatability of the measurements (error bars included but not visible) with standard deviations always lower than 5 %. Overall, ABSOR.B™ is a modern and affordable instrument to precisely determine the concentration of different solutes using the proper wavelength.
KEY TAKEAWAYS
- The versatility of the ABSOR.B™ allows the user to use the same instrument to measure the absorbance and transmittance of different solutions by selecting the proper wavelength through the variety of available cartridges.
- Calibration curves from standard samples can be stored into the Tablet App for a quick determination of the solution’s concentration.
- The modularity of the ABSOR.B™ allows the user to expand their testing platform as the needs evolve with multiple units, different cartridges for light emission and reception, and sample holders.
$7,500 per system
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