Ciara,

What You can do is spiking. Add a known amount of standard to your sample. The amount should be in the lower range of your calibration range but still easy to quantify (something like 20 mg/L in this case). If the difference between the spiked sample and the calibration( for 20 mg/l) is negligible then you have confirmation that your method is ok and that the sample contains below detection limit.

An other approach would be complete standard addition set but this is more time consuming.

Hi Kris,

Thank you I forgot to mention with my last run I added 2 ethylbutyrate in the run. However, I was unsure what concentration so I used a varying amounts with my mid point standard (50mg/L) and I tried 1mM, 2mM up to 20mM in vial concentration. I prepared the 2 ethylbutyrate with 12% formic acid and milliq water. So with this result am I looking at the amount in area the software is picking up or the peaks themselves? But I should re run this using the low range standard (20mg/L) and the same amount 2 ethybutyrate?

Thank you for taking the time to respond.

Ciara

Hi Ciara,

In my opinion having 10mg of VFA should not be a problem for GC analysis, unless the total volume exceeds by far 1L. If this is the case then you ought to concentrate your sample on some absorbing solid medium (trap) that you can desorb either on the GC itself by heating (try to find out about TENAX) or else to elute the solid trap so that extract concentration fall within your instrument sensitivity.

Good luck

J Pierre

Hi Jean Paul,

Thank you for the above comments. I am just reading about the TENAX packings, that is very interesting.

Ciara: Have you thought about methylating the fatty acids to convert them to methyl esters?