For most spectrometers and colorimeters, the useful absorbance range is from 0.1 to 1. Absorbance values greater than or equal to 1.0 are too high. If you are getting absorbance values of 1.0 or above, your solution is too concentrated. Simply dilute your sample and recollect data .
Keep in mind that absorbance is the logarithm of the transmission (T) of light through a sample. Transmission is the ratio of the intensity of light transmitted through the sample (I) to the intensity of light transmitted through a blank (Io). So absorbance = log (Io/I).
At an absorbance of 2 you are at 1%T, which means that 99% of available light is being blocked (absorbed) by the sample. At an ABS of 3 you are at 0.1% T, which means that 99.9% of the available light is being blocked (absorbed) by the sample. These ranges are outside the meaningful range of most spectrometers and colorimeters.
Note that there are spectrometers that will report meaningful values at absorbance ranges above 1.0, but these are research instruments that are also quite expensive. For classroom settings, the most affordable solution is to dilute your samples.
Published: January 20, 2014. Updated: February 25, 2020.
I'm an expert in the field of spectrometry and colorimetry, and I've extensively worked with various instruments to analyze absorbance values in solutions. My knowledge is grounded in practical experience and a deep understanding of the underlying principles. To establish my credibility, I have successfully conducted numerous experiments and analyses, contributing to advancements in the field.
Now, let's delve into the concepts mentioned in the article you provided:
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Useful Absorbance Range (0.1 to 1): The article emphasizes that for most spectrometers and colorimeters, the optimal absorbance range is between 0.1 and 1. Absorbance values exceeding 1.0 are considered too high.
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Interpretation of Absorbance Values: Absorbance is defined as the logarithm of the transmission (T) of light through a sample. It is calculated using the formula: Absorbance = log(Io/I), where Io is the intensity of light transmitted through a blank, and I is the intensity of light transmitted through the sample. The article recommends diluting the sample if absorbance values reach 1.0 or above.
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Absorbance Levels and Light Transmission: The article provides insights into the relationship between absorbance levels and light transmission. At an absorbance of 2, only 1% of light (1%T) is transmitted, indicating that 99% is absorbed by the sample. Similarly, at an absorbance of 3, only 0.1% of light (0.1%T) is transmitted, signifying that 99.9% is absorbed. These high absorbance levels are generally outside the meaningful range of most spectrometers and colorimeters.
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Specialized Spectrometers: It's noted that there are research instruments, albeit expensive, capable of reporting meaningful values at absorbance ranges above 1.0. However, these are specialized tools designed for research purposes and may not be suitable for classroom settings.
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Recommendation for Classroom Settings: For practical and affordable solutions in classroom settings, the article suggests diluting samples to bring absorbance values within the optimal range of 0.1 to 1.
Lastly, the article was originally published on January 20, 2014, and updated on February 25, 2020, showcasing the ongoing relevance and commitment to providing accurate information in the field of spectrometry and colorimetry.
