[sweet_question]

I have a calibration curve for methyl salicylate (MeS) from Gas Chromatography (GC).
Calibration curve point taken into account are 1ppm , 10ppm, 100ppm vs. respective area from GC .
I am trying to bubble MeS gas into impinger in known solution at known amount of quantity.
From this solution I can get area from GC.
Question is how I can calculate concentration of MeS bubbled in inpinger.
Points to be noted:
1) MeS used for calibration is in liquid state
2) Concentration of MeS stream to be calculated is in vapor phase
3) Molecular weight of MeS 152.1494 g/mol
4) Same solution used as a solvent for preparing calibration curve and solvent in impinge
Things I can’t Do: Considering weight of impinge before and after bubbling (too many removable parts )
Some Reference:
1ppm = 0.001gm/Lit = 1mg/L
10ppm = 0.01gm/Lit = 10mg/L
100ppm = 0.1gm/Lit = 100mg/L
Below conversion useful if quantity is in gases state
The conversion equation is based on 25 ºC and 1 atmosphere:
X ppm = (Y mg/m3)(24.45)/(molecular weight)


Pls Help !!
Thank you in advance

[JGK]

If you make up the solvent  in the impinger to a constant volume after bubbling the gas through, then the  only other parameter you need to know is the volume of gas which has passed through the impinger.

The measured concentration in ppm from the GC analysis can be used to calculate the amount of MeS collected from the gas. if you know the volume of gas which passed through the impinger you can calculate the MeS concentration in the gas.

If you add a fixed volume of solvent to the impinger, you may get evaporative loss during the bubbling process which will affect your result. I've found it's always better to make up the impinger contents to a fixed volume after the fact.

 

[sweet_question]

Thx for reply,
Some more specification,
Solvent used in the impinger is of constant volume, and it does not evoporate considerably even after 300min.
I know the volume of gas I am passing through the impinger,

Trouble is . 1) Calibration curve is obtain from the liquid solution
2) while back calculating for concentration in ppm from the impenger , I have to take into account that this will be gas phase

So If I dont consider this change I take into account :
[ A] Response Factor (RF)= Slope from calibration curve                
               
Analyte concentration CA [mg/L] = (RF) * GC area (from impenger solution)            
               
[C] Correct flow SC[L/min] =  Sample flow  * ( BP – PW / 760) * ( 293 / (273 + t) )                
   BP = Pressure at time of sampling , mmHg            
   PW = Partial pressure of water vapor at time t , mmHg            
   t      = Ambient temperature at time of sampling , ºC            
               
[D] Stock concentration, ppm = (CA / MW) *(22.4 / SC * ST) * 10E6
           MW = Molecular weight of MeS
           ST  = Sampling time
   

Where I am going wrong !!!!?         

If you make up the solvent  in the impinger to a constant volume after bubbling the gas through, then the  only other parameter you need to know is the volume of gas which has passed through the impinger.

The measured concentration in ppm from the GC analysis can be used to calculate the amount of MeS collected from the gas. if you know the volume of gas which passed through the impinger you can calculate the MeS concentration in the gas.

If you add a fixed volume of solvent to the impinger, you may get evaporative loss during the bubbling process which will affect your result. I've found it's always better to make up the impinger contents to a fixed volume after the fact.

 

[JGK]

As far as I can see all you need to do is work out the concentration of MeS in the impinger solution in whatever unit/mL are appropriate.

Use this value and the inpinger solution volume to get the total MeS in the collected sample.

Divide the total collected by the volume of gas sampled throught the impinger, you should now have a value (in g/L, or whatever mass/volume units you are working with). Convert this to a ppm value and you should be ok.

[sweet_question]

Still not getting what you want to say

"Divide the total collected by the volume of gas sampled throught the impinger" ... I cant weigh the difference in impinger before and after the sampling.

Can you be more elaborate please !!

As far as I can see all you need to do is work out the concentration of MeS in the impinger solution in whatever unit/mL are appropriate.

Use this value and the inpinger solution volume to get the total MeS in the collected sample.

Divide the total collected by the volume of gas sampled throught the impinger, you should now have a value (in g/L, or whatever mass/volume units you are working with). Convert this to a ppm value and you should be ok.

[JGK]

If you know the volume of gas you pass through the impinger and you have mesured the analyte concentration (mass/volume) in the impinger solution by GC

The next step is to calculate the amount (mass) of analyte in the volume of solution in the impinger .

If you know the amunt of analyte and the volume of gas, you can calculate the concentration (mass/volume) of analyte in the gas.

If you weigh the impinger before & after, you could arrive at a similar result but this will assume that only the analyte will be retained in the impinger liquid (also you wouldnt need to bother with the GC if you did it this way).