Determination of Formaldehyde in Tofu by Sequential Injection Analysis Using Acetoacetanilide as Hantzsch Reaction Reagent

Formaldehyde is a toxic and dangerous compound that is still often used freely by irresponsible traders or producers as food additives. At low concentrations, formaldehyde can cause eye, nose, throat and skin irritations. Exposure to large amounts of formaldehyde can cause severe pain, vomiting, coma, and even death. According to the International Program on Chemical Safety (IPCS), the threshold for formaldehyde in food that can still be tolerated in adult bodies is 1.5 mg to 14 mg per day while in a drinking water is 0.1 ppm. Determination of formaldehyde generally employ a titration method, which requires a large amount of sample and reagent, and long analysis time. This work aims to determine the formaldehyde in tofu commercially available in traditional markets of Malang City by Sequential Injection Analysis method using acetoacetanilide (AAA) at optimum conditions. Determination of formaldehyde is based on the Hantzsch reaction, which involves a cyclization between AAA and formaldehyde in the presence of ammonia so that it will produce a yellow dihydropyridine derivative product detected at a wavelength of 359 nm. The optimum condition for the formation of the reaction product occurred at an AAA concentration of 0.03 M, an ammonium acetate concentration of 1.5 M, a reaction time of 50 s and a flow rate of 75 µL/s. Excellent sensitivity and accuracy could be attributed to our developed formaldehyde detection method as the detection limit of 4.5 ppb and the recovery values of > 95 were achieved. Low reagent consumption, less waste production, and high throughput analysis are other advantages of our proposed method.