The Initial Volume of a Sample Is 100 μL $\frac{(400 \mu \mathrm{L})\left(\frac{25 \mu g}{\mathrm{~mL}}\right)}{100 \mu \mathrm{L}}$

question 4

Multiple Choice

The initial volume of a sample is 100 μL.It is diluted with saline by a factor of 4.The final volume is 400 μL.Testing the diluted sample finds an analyte concentration of 25 μg/mL.Which of the following expressions can be used to calculate the initial analyte concentration of this sample?

• A) \( \frac{(400 \mu \mathrm{L})\left(\frac{25 \mu g}{\mathrm{~mL}}\right)}{100 \mu \mathrm{L}} \)
• B) \( \frac{(100 \mu L)\left(\frac{25 \mu g}{m L}\right)}{400 \mu L} \)
• C) \( \frac{(400 \mu \mathrm{L})(100 \mu \mathrm{L})}{\frac{25 \mu \mathrm{g}}{\mathrm{mL}}} \)
• D) \( \frac{\text { (2) }\left(\frac{25 \mu g}{m L}\right)}{400 \mu \mathrm{L}} \)

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