How can i detect Formalin in food easily I am trying to detect formalin in different types of food. Formalin $(\ce{CH2(OH)2})$is an aqueous solution of formaldehyde, which is $\ce{CH2O}$ or $\ce{H2CO}$. I used many chemicals to do this, but every time I fail. Please help me to do this. I got some results in my test by using NFPA 704 and ChEMBL, but that is not enough to save all. I would like to make a simple and easy food formalin detector that can save all the people. Please help me or give me some direction.
Simple commercially available tests contain formaldehyde dehydrogenase. This enzyme selectively catalyzes the chemical reaction of formaldehyde:

$$\ce{CH2O + NAD+ + H2O -&gt; HCOO- + NADH + H+}$$

The enzymatic reaction is typically indicated by reduction of a tetrazolium salt to a coloured formazan dye.