The internal standard method of analysis was employed in GC for the determinatio
ID: 1004140 • Letter: T
Question
The internal standard method of analysis was employed in GC for the determination of TODD in river water. An analog ot TODD was used as an internal standard. The responses were 55 and 34 for the standard and the internal standard respectively. The internal standard procedure was as follows: 1.0 mg of internal standard was added to 2.0 mg of standard volume of 10.0 L. The internal standard was added to the unknown and the response Was 29 for the unknown and 25 for the internal standard. Find the concentration (in ppm the unknown?Explanation / Answer
Formula: Ax /[X] = F(As / [S])
Ax is response of standard
[X] is the concentration fo standard
F is response factor
As is response of internal standard
[S] is the concentration fo internal standard
First calculate the F:
(55/2.0 mg) = F (34/1.0 mg)
F = 0.81
For Unknown:
Ax /[X] = F(As / [S])
29/[X] = 0.81(25/1.0 mg)
[X] = 1.4 mg
Concentration of unknown is 1.4 mg/10.0 L = 0.14 mg/L = 0.14 ppm