Noel W Davies Hi Noel! Thanks for responding to my question! So, the strength of the formaldehyde solution is 37% - we prepare a stock that is 10,000 ppm in acidified ethanol and then dilute down to 1000 ppm. Should the area response (assuming 100% yield) for derivatized formaldehyde be the same as its pure standard at the same concentration, i.e., diethoxymethane at 1000 ppm?

I was wondering whether we made an error in calculation - but we getting the same behavior when we expose formic acid to acidified ethanol. The derivative of formic acid (ethyl formate) has a much greater area than the actual pure standard of ethyl formate at the same concentration!

We based all our investigation on research done by:Article Simultaneous determination of formic acid and formaldehyde i...

There will be an increase in concentration.

If you derivatise 1000mg of formaldehyde you will end up with 3468mg of diethoxymethane if the reaction is 1:1 by virtue of the different molar masses.

Patrick Mccabe Omg, thank you so much - this is what we have been suspecting. If that is the case, how do you determine the derivatization yield of such a reaction using a GC/FID? For example, diethoxymethane gives you an area of 2385 for 1000 ppm, while 1000 ppm of formaldehyde gives you an area of 9929.

If my calculations are right, if you had 100% yield, the expected area for the 1000ppm formaldehyde will be (2385/1000) x 3468 = 8271

So based on this you have a calculated yield of 120%.

I'm not sure of the accuracy of your analysis but there will some uncertainty there.

Patrick Mccabe You are a life-saver! Literally been busting my head with this lol

Thanks so much!

Glad to help.