Understanding Absorbance Values in UV Spectroscopy

In summary, the speaker is experiencing difficulties with their experiment due to obtaining an absorbance value of 6.0, which is above the recommended range for reliable results. This is because accurately measuring such a high absorbance is challenging. To solve this issue, the speaker is advised to dilute their sample to obtain a more reliable absorbance value within the range of 0.1-1.0.
  • #1
kokololo
1
0
Hi guys, please can you kindly help me. I am getting an absorbance of over 6.0Abs for my experiment. However, when I am reading posts they mention that an absorbance above 1 is not reliable. Please can you explain so that I can understand. Thanks
 
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  • #2
What it is that you don't understand here? It is hard to help on a dry facts not knowing why you have problems with them.

Generally speaking to measure that high absorbance you would need to be able to accurately measure intensity of radiation over 6 orders of magnitude, that's not trivial.
 
  • #3
An abosorbance value of 6.0 means that if you shine a light through the solution, only 0.0001% of the light passes through. Because it's difficult to accurately measure such a tiny amount of light, the absorbance values are not very reliable. To measure the absorbance of the solution, you should first dilute your sample so that the absorbance falls within a reliable range (generally ~ 0.1-1.0).
 

1. What is absorbance in UV spectroscopy?

Absorbance in UV spectroscopy is a measure of how much light is absorbed by a sample at a particular wavelength. It is related to the concentration and extinction coefficient of the sample.

2. How is absorbance measured in UV spectroscopy?

Absorbance is measured by passing a beam of UV light through a sample and measuring the amount of light that is transmitted through the sample. The amount of light absorbed is then calculated using the Beer-Lambert law.

3. What is the relationship between absorbance and concentration in UV spectroscopy?

The relationship between absorbance and concentration in UV spectroscopy is linear, following the Beer-Lambert law. This means that as the concentration of a sample increases, the absorbance also increases proportionally.

4. What is the purpose of using a reference cuvette in UV spectroscopy?

A reference cuvette is used in UV spectroscopy to calibrate the instrument and account for any background absorbance. This ensures accurate and precise measurements of the sample absorbance are obtained.

5. What factors can affect the absorbance measurement in UV spectroscopy?

Several factors can affect the absorbance measurement in UV spectroscopy, including the sample concentration, the path length of the sample, the solvent used, and any impurities in the sample. It is important to control these factors to ensure accurate and reliable results.

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