To find the concentration of DNA in a solution based on its absorbance at 260 nm, you can use the Beer-Lambert law, which relates absorbance (A) to concentration (C) and the molar absorptivity constant (ε). The formula can be expressed as:
\[ C = \frac{A}{k} \]
Where:
- \(A\) is the absorbance,
- \(k\) is the absorptivity constant, which is given as 50 ng/µL for DNA.
Step 1: Calculate concentration of DNA
Given:
- Absorbance (\(A\)) = 0.412,
- \(k\) (constant for DNA) = 50 ng/µL.
Using the formula: \[ C = \frac{0.412}{50} = 0.00824 \text{ µg/µL} \]
To convert to ng/µL (since 1 µg = 1000 ng): \[ C = 0.00824 \text{ µg/µL} \times 1000 = 8.24 \text{ ng/µL} \]
Step 2: Calculate expected absorbance for 125 ng/µL
To find the expected absorbance for a concentration of 125 ng/µL, use the formula: \[ A = C \times k \]
Where:
- \(C\) = 125 ng/µL,
- \(k\) = 50 ng/µL.
Calculating the expected absorbance: \[ A = 125 \text{ ng/µL} \times \frac{1}{50} = 2.5 \]
Summary of results for DNA:
- The concentration of DNA in the solution with an absorbance of 0.412 is 8.24 ng/µL.
- The expected absorbance of a DNA solution with a concentration of 125 ng/µL is 2.5.
Step 3: Calculate concentration of substance Z
For substance Z at 600 nm, using the same approach as above:
Given:
- Absorbance (\(A\)) = 0.15,
- Constant (\(k\)) for substance Z = 25 ng/µL.
Using the formula: \[ C = \frac{A}{k} \] Where:
- \(A\) = 0.15,
- \(k\) = 25 ng/µL.
Calculating concentration: \[ C = \frac{0.15}{25} = 0.006 \text{ µg/µL} \]
Converting to ng/µL: \[ C = 0.006 \text{ µg/µL} \times 1000 = 6 \text{ ng/µL} \]
Summary of results for substance Z:
- The concentration of substance Z with an absorbance of 0.15 is 6 ng/µL.
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