Chromatography Forum

Hi

A solution of 50 mL contains compound A with unknown concentration. The peak area from GC-MS for this compound is A1.
The same solution is treated to remove compound A. After treatment the solution volume is reduced to 30 mL and compound A also reduced to some extenet. The peak area from this sample is A2.

In this case how to calculate the removal % of compound A using peak area information?

Generally, we can calculate the removal % from peak area using the formula (A1-A2)/A1 *100.

How do we calculate the removal percentage when volume is changing? Do we need to consider the change in volume when the removal % is calculated from peak area?

Thanks

What if you did your calculation based on area/mL ?

%removal = [(A1/50mL) - (A2/30mL)] / (A1/50mL) x 100

What if you did your calculation based on area/mL ?

%removal = [(A1/50mL) - (A2/30mL)] / (A1/50mL) x 100

That would be the proper calculation, assuming that the response versus concentration is perfectly linear, which many times for GC/MS is not true.

If the concentration in the ending sample is within 30% of the concentration of the original sample you might get an accurate number, but the farther away you get from the original concentration the more inaccurate it could be.

In addition the response factor for A1 and A2 must be the same so the mass can be calculated and the change in %Concentration is expressed as w/w.