A standard solution containing sarin (16 µg/mL) and the internal standard trieth

Question

A standard solution containing sarin (16 µg/mL) and the internal standard triethylphosphate (TEP) (10 µg/mL) was analyzed and found to have peak areas of 75,324 (sarin) and 67,346 (TEP).

A one gram soil sample was spiked with 100 ?L of 50 µg/mL of triethylphosphate and extracted according to the procedure described in #2. The sarin peak area was 50,000 and the TEP peak area was 36,000. (Assume the extraction efficiency is the same for sarin and TEP.)

What is the mass of sarin in the one gram sample of soil in units of µg?

For reference the procedure of #2 is as follows: One gram soil samples were prepared by spiking with nerve agents, such as sarin, and extracting with twice with 2 mL of dichloromethane by ultrasonic vibration (10 min). The extract was concentrated to 0.3 mL by nitrogen blow-down.

Explanation / Answer

Given concentration of sarin =16 micro

Area=50000

number of samples=50000/10=5000

m=1000*16/140.09*10^-6*5000

=16000/700450*10^-6

=0.22 micro g/mol

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