Solving the Beer-Lambert Equation for Lactate Solution

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In summary, the conversation discusses using the Lambert-Beer equation to plot the optical density of a lactate solution. The equation is A = εℓC, with a path length of 1 cm. The person is trying to use this equation to determine the concentration of lactate in a solution, but is having trouble getting accurate results. They mention that Beer's law is only accurate for values of A between 0.1 and 1.0, and that they are having difficulty measuring absorption values outside of this range. They also mention using a different formula to get a closer approximation to the example graph, but they do not understand the reasoning behind it.
  • #1
nobahar
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Homework Statement


I need to use the Lambert-Beer equation to plot optical density of a lactate solution.

Homework Equations


[tex]A=\varepsilon\ell C[/tex]
(The path length is 1 cm)

The Attempt at a Solution


This is one of my four samples (if you can show me where I'm going wrong with this then I can apply the correction to the others):
2.22 [tex]\mu[/tex]mol in 1.5ml, therefore there is 0.296 [tex]\mu[/tex]mol in 0.2ml
This info seems to match to the example graph I have.
But using the formula above, where [tex]\varepsilon[/tex]=6.22 for micromol/ml, I get:
6.22 x (0.296/0.2) micromol/ml = 9.2056
This doesn't match up with the graph I have! Any help appreciated! Please!:redface:
 
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  • #2
Beer's law is accurate only for values of A from about 0.1 to 1.0. Experimentally, it is difficult to accurately measure absorption values outside this range.
 
  • #3
That's the main problem, the results from the example graph are at a maximum of 0.4 for the absorption at 340nm (y-axis) when plotted against amount in micromoles up to 0.4 on the x-axis.
I can get a fairly close approximation (the graph itself is supposed to be an estimate) if I use the following formula:
(amount in micromoles x amount in ml) x 6.22. But this equation makes no sense; or at least I can't see the reasoning behind it.
 
  • #4
The slope of the best fit line to the graph should give you ε.
 

1. What is the Beer-Lambert Equation and how is it used to solve for lactate solution?

The Beer-Lambert Equation is a mathematical formula used to relate the concentration of a solution to its absorbance. It is used in conjunction with a spectrophotometer to measure the absorbance of a sample at a specific wavelength. By using the Beer-Lambert Equation, the concentration of lactate in a solution can be determined by measuring its absorbance and plugging the values into the equation.

2. What factors influence the accuracy of the Beer-Lambert Equation when solving for lactate solution?

There are several factors that can affect the accuracy of the Beer-Lambert Equation when solving for lactate solution. These include the purity and stability of the lactate solution, the wavelength of light used for measurement, and any interfering substances present in the solution. It is important to carefully control these factors to ensure accurate results.

3. Can the Beer-Lambert Equation be used to measure the concentration of lactate in any type of solution?

No, the Beer-Lambert Equation is specific to solutions that follow the principles of Beer's Law, which states that the absorbance of a solution is directly proportional to its concentration. Some solutions, such as those with highly concentrated or colored substances, may not follow Beer's Law and therefore cannot be accurately measured using this equation.

4. How does the Beer-Lambert Equation account for dilution of the lactate solution?

The Beer-Lambert Equation takes into account dilution by incorporating the path length of the solution into the equation. The path length is the distance that light travels through the solution, and it is directly proportional to the concentration of the solution. Therefore, as the solution is diluted, the path length decreases and the absorbance also decreases, resulting in a lower concentration measurement.

5. Are there any limitations to using the Beer-Lambert Equation for measuring lactate solution?

Yes, there are some limitations to using the Beer-Lambert Equation for measuring lactate solution. One limitation is that the equation assumes a linear relationship between concentration and absorbance, which may not hold true for all solutions. Additionally, the equation may not be accurate for solutions with high concentrations or for solutions containing multiple absorbing substances. It is important to validate the results obtained from the Beer-Lambert Equation using other methods to ensure accuracy.

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