What is the concentration of RNA in the diluted sample with A260 0.210 at 1:200?

What is the concentration of RNA in the diluted sample with A260 0.210 at 1:200?

• A. 8.4 μg/mL
• B. 1680 μg/mL
• C. 0.210 μg/mL
• D. 420 μg/mL

Answer: (A)

The amount of RNA is estimated from absorbance at 260 nm using the RNA extinction coefficient: about 40 μg/mL per unit of A260. Since the diluted sample’s absorbance is 0.210, the RNA concentration in that diluted solution is 0.210 × 40 = 8.4 μg/mL. The 1:200 dilution tells you how concentrated the original sample would be (multiply by 200 to get the undiluted concentration), which would be 8.4 × 200 = 1680 μg/mL, but the question asks for the concentration in the diluted sample. So the correct value is 8.4 μg/mL.

The amount of RNA is estimated from absorbance at 260 nm using the RNA extinction coefficient: about 40 μg/mL per unit of A260. Since the diluted sample’s absorbance is 0.210, the RNA concentration in that diluted solution is 0.210 × 40 = 8.4 μg/mL. The 1:200 dilution tells you how concentrated the original sample would be (multiply by 200 to get the undiluted concentration), which would be 8.4 × 200 = 1680 μg/mL, but the question asks for the concentration in the diluted sample. So the correct value is 8.4 μg/mL.