Hi, I am developing a GC/FID method for a 6890 that characterizes and quantitates halogenated analytes used in vapor degreasing. My problem is that my results are not precise and I do not have a calculation method to express my results as weight percent (

I have attached a copy of the method I am currently using. Please review it and let me know if you can assist me. 

Thank you!

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  • Hi megaflorch,

    The only suggestion I have on the acquisition portion of this method is that your gas save time is very short and may actually interfere with the sample if it hasn't made it on column. You have 0.75 minutes, I would lengthen out to 2 minutes. One other , unrelated to sample results, but more for robustness of the method I see is that you have a very high makeup gas flow for your FID. This may cause some lighting issues if the jet becomes slightly restricted at some point, I would suggest dropping the makeup from 30 to something like 10 ml/min. For troubleshooting purposes, you can also try a viscosity delay of 3 on the injection to see if there is a difference and this is just a suggestion since I dont know what solvent you are using.

     

    Regards

    James

  • Thanks James, I will certainly try your suggestions. I suppose that I really do not have too many issues with the parameters of the method, but it is mostly pertaining to my stock preparation and sample preparation and calculations.

    For example, my calibration stock is composed of four analytes, each weighed to 100g+/- 0.001 and combined in the stock solution. Should I calculate each respective analytes concentration? And if I do that, how would I go about it? Determine each density and convert my units appropriately? Im not sure. Also, from my stock solution, I am weighing out my calibration standards instead of just simplifying my concentration. Is there a way to enter the calculation parameter for determining weight percent (w/w) into Chemstation and have it calculate my results? Any additional insights are appreciated.

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  • Thanks James, I will certainly try your suggestions. I suppose that I really do not have too many issues with the parameters of the method, but it is mostly pertaining to my stock preparation and sample preparation and calculations.

    For example, my calibration stock is composed of four analytes, each weighed to 100g+/- 0.001 and combined in the stock solution. Should I calculate each respective analytes concentration? And if I do that, how would I go about it? Determine each density and convert my units appropriately? Im not sure. Also, from my stock solution, I am weighing out my calibration standards instead of just simplifying my concentration. Is there a way to enter the calculation parameter for determining weight percent (w/w) into Chemstation and have it calculate my results? Any additional insights are appreciated.

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